Add ability to stream blocks and tidy errors

historic/src/storage.rs

@@ -216,7 +216,7 @@ where
     > {
         use futures::stream::StreamExt;
         use subxt_rpcs::methods::chain_head::{
-            ArchiveStorageEvent, StorageQuery, StorageQueryType,
+            ArchiveStorageEvent, ArchiveStorageQuery, StorageQueryType,
         };
 
         let expected_num_keys = with_info!(info = &*self.info => {
@@ -235,9 +235,10 @@ where
         let block_hash = self.client.block_hash();
         let key_bytes = self.key(keys)?;
 
-        let items = std::iter::once(StorageQuery {
+        let items = std::iter::once(ArchiveStorageQuery {
             key: &*key_bytes,
             query_type: StorageQueryType::DescendantsValues,
+            pagination_start_key: None,
         });
 
         let sub = self
@@ -297,11 +298,14 @@ where
     T: Config + 'atblock,
     Client: OnlineClientAtBlockT<'atblock, T>,
 {
-    use subxt_rpcs::methods::chain_head::{ArchiveStorageEvent, StorageQuery, StorageQueryType};
+    use subxt_rpcs::methods::chain_head::{
+        ArchiveStorageEvent, ArchiveStorageQuery, StorageQueryType,
+    };
 
-    let query = StorageQuery {
+    let query = ArchiveStorageQuery {
         key: key_bytes,
         query_type: StorageQueryType::Value,
+        pagination_start_key: None,
     };
 
     let mut response_stream = client

new/src/backend.rs

@@ -6,10 +6,10 @@
 //! the necessary information (probably from a JSON-RPC API, but that's up to the
 //! implementation).
 
-mod chain_head;
 mod archive;
-mod legacy;
+mod chain_head;
 mod combined;
+mod legacy;
 mod utils;
 
 use crate::config::{Config, HashFor};
@@ -22,23 +22,10 @@ use std::sync::Arc;
 use subxt_metadata::Metadata;
 
 // Expose our various backends.
-pub use chain_head::{
+pub use archive::ArchiveBackend;
-    ChainHeadBackend,
+pub use chain_head::{ChainHeadBackend, ChainHeadBackendBuilder, ChainHeadBackendDriver};
-    ChainHeadBackendBuilder,
+pub use combined::{CombinedBackend, CombinedBackendBuilder, CombinedBackendDriver};
-    ChainHeadBackendDriver,
+pub use legacy::{LegacyBackend, LegacyBackendBuilder};
-};
-pub use archive::{
-    ArchiveBackend
-};
-pub use legacy::{
-    LegacyBackend,
-    LegacyBackendBuilder
-};
-pub use combined::{
-    CombinedBackend,
-    CombinedBackendBuilder,
-    CombinedBackendDriver
-};
 
 /// Prevent the backend trait being implemented externally.
 #[doc(hidden)]
@@ -78,7 +65,10 @@ pub trait Backend<T: Config>: sealed::Sealed + Send + Sync + 'static {
     /// multiple block hashes correspond to the given number (ie if the number is greater
     /// than that of the latest finalized block and some forks exist). Nevertheless, it could
     /// still return the hash to a block on some fork that is pruned.
-    async fn block_number_to_hash(&self, number: u64) -> Result<Option<BlockRef<HashFor<T>>>, BackendError>;
+    async fn block_number_to_hash(
+        &self,
+        number: u64,
+    ) -> Result<Option<BlockRef<HashFor<T>>>, BackendError>;
 
     /// Get a block header.
     async fn block_header(&self, at: HashFor<T>) -> Result<Option<T::Header>, BackendError>;

new/src/backend/archive.rs

@@ -12,20 +12,17 @@
 
 mod storage_stream;
 
-use subxt_rpcs::methods::ChainHeadRpcMethods;
 use crate::backend::{
-    Backend, BlockRef, StorageResponse, StreamOf, StreamOfResults,
+    Backend, BlockRef, StorageResponse, StreamOf, StreamOfResults, TransactionStatus, utils::retry,
-    TransactionStatus, utils::retry,
 };
 use crate::config::{Config, HashFor, RpcConfigFor};
 use crate::error::BackendError;
 use async_trait::async_trait;
 use futures::StreamExt;
-use subxt_rpcs::RpcClient;
-use subxt_rpcs::methods::chain_head::{
-    ArchiveStorageQuery, ArchiveCallResult, StorageQueryType,
-};
 use storage_stream::ArchiveStorageStream;
+use subxt_rpcs::RpcClient;
+use subxt_rpcs::methods::ChainHeadRpcMethods;
+use subxt_rpcs::methods::chain_head::{ArchiveCallResult, ArchiveStorageQuery, StorageQueryType};
 
 /// The archive backend.
 #[derive(Debug, Clone)]
@@ -36,7 +33,7 @@ pub struct ArchiveBackend<T: Config> {
 
 impl<T: Config> ArchiveBackend<T> {
     /// Configure and construct an [`ArchiveBackend`] and the associated [`ChainHeadBackendDriver`].
-    pub fn new(client: impl Into<RpcClient>,) -> ArchiveBackend<T> {
+    pub fn new(client: impl Into<RpcClient>) -> ArchiveBackend<T> {
         let methods = ChainHeadRpcMethods::new(client.into());
 
         ArchiveBackend { methods }
@@ -50,7 +47,8 @@ impl<T: Config> Backend<T> for ArchiveBackend<T> {
         keys: Vec<Vec<u8>>,
         at: HashFor<T>,
     ) -> Result<StreamOfResults<StorageResponse>, BackendError> {
-        let queries = keys.into_iter()
+        let queries = keys
+            .into_iter()
             .map(|key| ArchiveStorageQuery {
                 key: key,
                 query_type: StorageQueryType::Value,
@@ -58,12 +56,17 @@ impl<T: Config> Backend<T> for ArchiveBackend<T> {
             })
             .collect();
 
-        let stream = ArchiveStorageStream::new(at, self.methods.clone(), queries).map(|item| {
+        let stream = ArchiveStorageStream::new(at, self.methods.clone(), queries)
-            match item {
+            .map(|item| match item {
                 Err(e) => Some(Err(e)),
-                Ok(item) => item.value.map(|val| Ok(StorageResponse { key: item.key.0, value: val.0 }))
+                Ok(item) => item.value.map(|val| {
-            }
+                    Ok(StorageResponse {
-        }).filter_map(async |item| item);
+                        key: item.key.0,
+                        value: val.0,
+                    })
+                }),
+            })
+            .filter_map(async |item| item);
 
         Ok(StreamOf(Box::pin(stream)))
     }
@@ -74,19 +77,18 @@ impl<T: Config> Backend<T> for ArchiveBackend<T> {
         at: HashFor<T>,
     ) -> Result<StreamOfResults<Vec<u8>>, BackendError> {
         let queries = std::iter::once(ArchiveStorageQuery {
-                key: key,
+            key: key,
-                // Just ask for the hash and then ignore it and return keys
+            // Just ask for the hash and then ignore it and return keys
-                query_type: StorageQueryType::DescendantsHashes,
+            query_type: StorageQueryType::DescendantsHashes,
-                pagination_start_key: None,
+            pagination_start_key: None,
-            })
+        })
-            .collect();
+        .collect();
 
-        let stream = ArchiveStorageStream::new(at, self.methods.clone(), queries).map(|item| {
+        let stream =
-            match item {
+            ArchiveStorageStream::new(at, self.methods.clone(), queries).map(|item| match item {
                 Err(e) => Err(e),
-                Ok(item) => Ok(item.key.0)
+                Ok(item) => Ok(item.key.0),
-            }
+            });
-        });
 
         Ok(StreamOf(Box::pin(stream)))
     }
@@ -97,18 +99,23 @@ impl<T: Config> Backend<T> for ArchiveBackend<T> {
         at: HashFor<T>,
     ) -> Result<StreamOfResults<StorageResponse>, BackendError> {
         let queries = std::iter::once(ArchiveStorageQuery {
-                key: key,
+            key: key,
-                query_type: StorageQueryType::DescendantsValues,
+            query_type: StorageQueryType::DescendantsValues,
-                pagination_start_key: None,
+            pagination_start_key: None,
-            })
+        })
-            .collect();
+        .collect();
 
-        let stream = ArchiveStorageStream::new(at, self.methods.clone(), queries).map(|item| {
+        let stream = ArchiveStorageStream::new(at, self.methods.clone(), queries)
-            match item {
+            .map(|item| match item {
                 Err(e) => Some(Err(e)),
-                Ok(item) => item.value.map(|val| Ok(StorageResponse { key: item.key.0, value: val.0 }))
+                Ok(item) => item.value.map(|val| {
-            }
+                    Ok(StorageResponse {
-        }).filter_map(async |item| item);
+                        key: item.key.0,
+                        value: val.0,
+                    })
+                }),
+            })
+            .filter_map(async |item| item);
 
         Ok(StreamOf(Box::pin(stream)))
     }
@@ -121,9 +128,15 @@ impl<T: Config> Backend<T> for ArchiveBackend<T> {
         .await
     }
 
-    async fn block_number_to_hash(&self, number: u64) -> Result<Option<BlockRef<HashFor<T>>>, BackendError> {
+    async fn block_number_to_hash(
+        &self,
+        number: u64,
+    ) -> Result<Option<BlockRef<HashFor<T>>>, BackendError> {
         retry(|| async {
-            let mut hashes = self.methods.archive_v1_hash_by_height(number as usize).await?;
+            let mut hashes = self
+                .methods
+                .archive_v1_hash_by_height(number as usize)
+                .await?;
             if let (Some(hash), None) = (hashes.pop(), hashes.pop()) {
                 // One hash; return it.
                 Ok(Some(BlockRef::from_hash(hash)))
@@ -131,7 +144,8 @@ impl<T: Config> Backend<T> for ArchiveBackend<T> {
                 // More than one; return None.
                 Ok(None)
             }
-        }).await
+        })
+        .await
     }
 
     async fn block_header(&self, at: HashFor<T>) -> Result<Option<T::Header>, BackendError> {
@@ -147,9 +161,7 @@ impl<T: Config> Backend<T> for ArchiveBackend<T> {
             let Some(exts) = self.methods.archive_v1_body(at).await? else {
                 return Ok(None);
             };
-            Ok(Some(
+            Ok(Some(exts.into_iter().map(|ext| ext.0).collect()))
-                exts.into_iter().map(|ext| ext.0).collect()
-            ))
         })
         .await
     }
@@ -159,7 +171,9 @@ impl<T: Config> Backend<T> for ArchiveBackend<T> {
             let height = self.methods.archive_v1_finalized_height().await?;
             let mut hashes = self.methods.archive_v1_hash_by_height(height).await?;
             let Some(hash) = hashes.pop() else {
-                return Err(BackendError::Other("Multiple hashes not expected at a finalized height".into()))
+                return Err(BackendError::Other(
+                    "Multiple hashes not expected at a finalized height".into(),
+                ));
             };
             Ok(BlockRef::from_hash(hash))
         })
@@ -170,21 +184,27 @@ impl<T: Config> Backend<T> for ArchiveBackend<T> {
         &self,
         _hasher: T::Hasher,
     ) -> Result<StreamOfResults<(T::Header, BlockRef<HashFor<T>>)>, BackendError> {
-        Err(BackendError::Other("The archive backend cannot stream block headers".into()))
+        Err(BackendError::Other(
+            "The archive backend cannot stream block headers".into(),
+        ))
     }
 
     async fn stream_best_block_headers(
         &self,
         _hasher: T::Hasher,
     ) -> Result<StreamOfResults<(T::Header, BlockRef<HashFor<T>>)>, BackendError> {
-        Err(BackendError::Other("The archive backend cannot stream block headers".into()))
+        Err(BackendError::Other(
+            "The archive backend cannot stream block headers".into(),
+        ))
     }
 
     async fn stream_finalized_block_headers(
         &self,
         _hasher: T::Hasher,
     ) -> Result<StreamOfResults<(T::Header, BlockRef<HashFor<T>>)>, BackendError> {
-        Err(BackendError::Other("The archive backend cannot stream block headers".into()))
+        Err(BackendError::Other(
+            "The archive backend cannot stream block headers".into(),
+        ))
     }
 
     async fn submit_transaction(
@@ -201,7 +221,10 @@ impl<T: Config> Backend<T> for ArchiveBackend<T> {
         call_parameters: Option<&[u8]>,
         at: HashFor<T>,
     ) -> Result<Vec<u8>, BackendError> {
-        let res = self.methods.archive_v1_call(at, method, call_parameters.unwrap_or(&[])).await?;
+        let res = self
+            .methods
+            .archive_v1_call(at, method, call_parameters.unwrap_or(&[]))
+            .await?;
         match res {
             ArchiveCallResult::Success(bytes) => Ok(bytes.0),
             ArchiveCallResult::Error(e) => Err(BackendError::other(e)),
@@ -209,5 +232,4 @@ impl<T: Config> Backend<T> for ArchiveBackend<T> {
     }
 }
 
- impl<T: Config> crate::backend::sealed::Sealed for ArchiveBackend<T> {}
+impl<T: Config> crate::backend::sealed::Sealed for ArchiveBackend<T> {}
-

new/src/backend/archive/storage_stream.rs

@@ -1,13 +1,15 @@
-use std::collections::VecDeque;
-use subxt_rpcs::Error as RpcError;
-use subxt_rpcs::methods::chain_head::{ArchiveStorageQuery, ArchiveStorageSubscription, ArchiveStorageEvent, ArchiveStorageEventItem};
-use std::pin::Pin;
-use std::future::Future;
-use futures::{FutureExt, Stream, StreamExt};
-use std::task::{Context, Poll};
-use crate::error::BackendError;
 use crate::config::{Config, HashFor, RpcConfigFor};
+use crate::error::BackendError;
+use futures::{FutureExt, Stream, StreamExt};
+use std::collections::VecDeque;
+use std::future::Future;
+use std::pin::Pin;
+use std::task::{Context, Poll};
+use subxt_rpcs::Error as RpcError;
 use subxt_rpcs::methods::ChainHeadRpcMethods;
+use subxt_rpcs::methods::chain_head::{
+    ArchiveStorageEvent, ArchiveStorageEventItem, ArchiveStorageQuery, ArchiveStorageSubscription,
+};
 
 pub struct ArchiveStorageStream<T: Config> {
     at: HashFor<T>,
@@ -19,15 +21,21 @@ pub struct ArchiveStorageStream<T: Config> {
 enum StreamState<T: Config> {
     GetSubscription {
         current_query: ArchiveStorageQuery<Vec<u8>>,
-        sub_fut: Pin<Box<dyn Future<Output = Result<ArchiveStorageSubscription<HashFor<T>>, RpcError>> + Send + 'static>>
+        sub_fut: Pin<
+            Box<
+                dyn Future<Output = Result<ArchiveStorageSubscription<HashFor<T>>, RpcError>>
+                    + Send
+                    + 'static,
+            >,
+        >,
     },
     RunSubscription {
         current_query: ArchiveStorageQuery<Vec<u8>>,
-        sub: ArchiveStorageSubscription<HashFor<T>>
+        sub: ArchiveStorageSubscription<HashFor<T>>,
     },
 }
 
-impl <T: Config> ArchiveStorageStream<T> {
+impl<T: Config> ArchiveStorageStream<T> {
     /// Fetch descendant keys.
     pub fn new(
         at: HashFor<T>,
@@ -69,27 +77,23 @@ impl<T: Config> Stream for ArchiveStorageStream<T> {
                             pagination_start_key: query.pagination_start_key.as_deref(),
                         });
 
-                        methods.archive_v1_storage(
+                        methods.archive_v1_storage(at, query, None).await
-                            at, 
-                            query, 
-                            None
-                        ).await
                     };
 
                     this.state = Some(StreamState::GetSubscription {
                         current_query,
-                        sub_fut: Box::pin(sub_fut) 
+                        sub_fut: Box::pin(sub_fut),
                     });
-                },
+                }
                 // We're getting our subscription stream for the current query.
-                Some(StreamState::GetSubscription { current_query, mut sub_fut }) => {
+                Some(StreamState::GetSubscription {
+                    current_query,
+                    mut sub_fut,
+                }) => {
                     match sub_fut.poll_unpin(cx) {
                         Poll::Ready(Ok(sub)) => {
-                            this.state = Some(StreamState::RunSubscription { 
+                            this.state = Some(StreamState::RunSubscription { current_query, sub });
-                                current_query, 
+                        }
-                                sub
-                            });
-                        },
                         Poll::Ready(Err(e)) => {
                             if e.is_disconnected_will_reconnect() {
                                 // Push the query back onto the queue to try again
@@ -98,19 +102,22 @@ impl<T: Config> Stream for ArchiveStorageStream<T> {
                             }
 
                             this.state = None;
-                            return Poll::Ready(Some(Err(e.into())))
+                            return Poll::Ready(Some(Err(e.into())));
                         }
                         Poll::Pending => {
                             this.state = Some(StreamState::GetSubscription {
                                 current_query,
-                                sub_fut
+                                sub_fut,
                             });
-                            return Poll::Pending
+                            return Poll::Pending;
-                        },
+                        }
                     }
-                },
+                }
                 // Running the subscription and returning results.
-                Some(StreamState::RunSubscription { current_query, mut sub }) => {
+                Some(StreamState::RunSubscription {
+                    current_query,
+                    mut sub,
+                }) => {
                     match sub.poll_next_unpin(cx) {
                         Poll::Ready(Some(Ok(val))) => {
                             match val {
@@ -123,9 +130,9 @@ impl<T: Config> Stream for ArchiveStorageStream<T> {
                                             // At the time of writing, it's not clear if paginationStartKey
                                             // starts from the key itself or the first key after it:
                                             // https://github.com/paritytech/json-rpc-interface-spec/issues/176
-                                            pagination_start_key: Some(item.key.0.clone())
+                                            pagination_start_key: Some(item.key.0.clone()),
                                         },
-                                        sub 
+                                        sub,
                                     });
 
                                     // We treat `paginationStartKey` as being the key we want results to begin _after_.
@@ -140,17 +147,17 @@ impl<T: Config> Stream for ArchiveStorageStream<T> {
                                     }
 
                                     return Poll::Ready(Some(Ok(item)));
-                                },
+                                }
                                 ArchiveStorageEvent::Error(e) => {
                                     this.state = None;
-                                    return Poll::Ready(Some(Err(BackendError::other(e.error))))
+                                    return Poll::Ready(Some(Err(BackendError::other(e.error))));
-                                },
+                                }
                                 ArchiveStorageEvent::Done => {
                                     this.state = None;
                                     continue;
-                                },
+                                }
                             }
-                        },
+                        }
                         Poll::Ready(Some(Err(e))) => {
                             if e.is_disconnected_will_reconnect() {
                                 // Put the current query back into the queue and retry.
@@ -167,11 +174,9 @@ impl<T: Config> Stream for ArchiveStorageStream<T> {
                             this.state = None;
                             continue;
                         }
-                        Poll::Pending => {
+                        Poll::Pending => return Poll::Pending,
-                            return Poll::Pending
-                        },
                     }
-                },
+                }
             }
         }
     }

new/src/backend/chain_head.rs

@@ -13,11 +13,10 @@ mod follow_stream_driver;
 mod follow_stream_unpin;
 mod storage_items;
 
-use subxt_rpcs::methods::ChainHeadRpcMethods;
 use self::follow_stream_driver::FollowStreamFinalizedHeads;
 use crate::backend::{
-    Backend, BlockRef, BlockRefT, StorageResponse, StreamOf, StreamOfResults,
+    Backend, BlockRef, BlockRefT, StorageResponse, StreamOf, StreamOfResults, TransactionStatus,
-    TransactionStatus, utils::retry,
+    utils::retry,
 };
 use crate::config::{Config, Hash, HashFor, RpcConfigFor};
 use crate::error::{BackendError, RpcError};
@@ -29,6 +28,7 @@ use std::collections::HashMap;
 use std::task::Poll;
 use storage_items::StorageItems;
 use subxt_rpcs::RpcClient;
+use subxt_rpcs::methods::ChainHeadRpcMethods;
 use subxt_rpcs::methods::chain_head::{
     FollowEvent, MethodResponse, StorageQuery, StorageQueryType, StorageResultType,
 };
@@ -373,8 +373,13 @@ impl<T: Config> Backend<T> for ChainHeadBackend<T> {
         .await
     }
 
-    async fn block_number_to_hash(&self, _number: u64) -> Result<Option<BlockRef<HashFor<T>>>, BackendError> {
+    async fn block_number_to_hash(
-        Err(BackendError::other("The ChainHead V1 RPCs do not support obtaining a block hash from a number."))
+        &self,
+        _number: u64,
+    ) -> Result<Option<BlockRef<HashFor<T>>>, BackendError> {
+        Err(BackendError::other(
+            "The ChainHead V1 RPCs do not support obtaining a block hash from a number.",
+        ))
     }
 
     async fn block_header(&self, at: HashFor<T>) -> Result<Option<T::Header>, BackendError> {
@@ -567,24 +572,29 @@ pub(crate) async fn submit_transaction_ignoring_follow_events<T: Config>(
                     RpcTransactionStatus::Broadcasted => TransactionStatus::Broadcasted,
                     RpcTransactionStatus::BestChainBlockIncluded { block: None } => {
                         TransactionStatus::NoLongerInBestBlock
-                    },
+                    }
                     RpcTransactionStatus::BestChainBlockIncluded { block: Some(block) } => {
-                        TransactionStatus::InBestBlock { hash: BlockRef::from_hash(block.hash) }
+                        TransactionStatus::InBestBlock {
-                    },
+                            hash: BlockRef::from_hash(block.hash),
+                        }
+                    }
                     RpcTransactionStatus::Finalized { block } => {
-                        TransactionStatus::InFinalizedBlock { hash: BlockRef::from_hash(block.hash) }
+                        TransactionStatus::InFinalizedBlock {
-                    },
+                            hash: BlockRef::from_hash(block.hash),
+                        }
+                    }
                     RpcTransactionStatus::Error { error } => {
                         TransactionStatus::Error { message: error }
-                    },
+                    }
                     RpcTransactionStatus::Invalid { error } => {
                         TransactionStatus::Invalid { message: error }
-                    },
+                    }
                     RpcTransactionStatus::Dropped { error } => {
                         TransactionStatus::Dropped { message: error }
-                    },
+                    }
                 }
-            }).map_err(Into::into)
+            })
+            .map_err(Into::into)
         });
 
     Ok(StreamOf(Box::pin(tx_progress)))
@@ -644,9 +654,7 @@ async fn submit_transaction_tracking_follow_events<T: Config>(
             // Poll for a follow event, and error if the stream has unexpectedly ended.
             let follow_ev_poll = match seen_blocks_sub.poll_next_unpin(cx) {
                 Poll::Ready(None) => {
-                    return Poll::Ready(err_other(
+                    return Poll::Ready(err_other("chainHead_follow stream ended unexpectedly"));
-                        "chainHead_follow stream ended unexpectedly",
-                    ));
                 }
                 Poll::Ready(Some(follow_ev)) => Poll::Ready(follow_ev),
                 Poll::Pending => Poll::Pending,
@@ -671,10 +679,8 @@ async fn submit_transaction_tracking_follow_events<T: Config>(
                     }
                     FollowEvent::Finalized(ev) => {
                         for block_ref in ev.finalized_block_hashes {
-                            seen_blocks.insert(
+                            seen_blocks
-                                block_ref.hash(),
+                                .insert(block_ref.hash(), (SeenBlockMarker::Finalized, block_ref));
-                                (SeenBlockMarker::Finalized, block_ref),
-                            );
                         }
                     }
                     FollowEvent::Stop => {
@@ -694,9 +700,7 @@ async fn submit_transaction_tracking_follow_events<T: Config>(
             // If we have a finalized hash, we are done looking for tx events and we are just waiting
             // for a pinned block with a matching hash (which must appear eventually given it's finalized).
             if let Some(hash) = &finalized_hash {
-                if let Some((SeenBlockMarker::Finalized, block_ref)) =
+                if let Some((SeenBlockMarker::Finalized, block_ref)) = seen_blocks.remove(hash) {
-                    seen_blocks.remove(hash)
-                {
                     // Found it! Hand back the event with a pinned block. We're done.
                     done = true;
                     let ev = TransactionStatus::InFinalizedBlock {

new/src/backend/chain_head/follow_stream.rs

@@ -103,7 +103,9 @@ impl<Hash> FollowStream<Hash> {
     }
 
     /// Create a new [`FollowStream`] given the RPC methods.
-    pub fn from_methods<T: Config>(methods: ChainHeadRpcMethods<RpcConfigFor<T>>) -> FollowStream<HashFor<T>> {
+    pub fn from_methods<T: Config>(
+        methods: ChainHeadRpcMethods<RpcConfigFor<T>>,
+    ) -> FollowStream<HashFor<T>> {
         FollowStream {
             stream_getter: Box::new(move || {
                 let methods = methods.clone();
@@ -113,7 +115,7 @@ impl<Hash> FollowStream<Hash> {
                     // Extract the subscription ID:
                     let Some(sub_id) = stream.subscription_id().map(ToOwned::to_owned) else {
                         return Err(BackendError::other(
-                            "Subscription ID expected for chainHead_follow response, but not given"
+                            "Subscription ID expected for chainHead_follow response, but not given",
                         ));
                     };
                     // Map stream errors into the higher level subxt one:

new/src/backend/combined.rs

@@ -7,19 +7,16 @@
 
 use crate::backend::chain_head::ChainHeadBackendDriver;
 use crate::backend::{
-    legacy::LegacyBackend,
+    Backend, BlockRef, StorageResponse, StreamOfResults, TransactionStatus,
-    chain_head::ChainHeadBackend,
+    archive::ArchiveBackend, chain_head::ChainHeadBackend, legacy::LegacyBackend,
-    archive::ArchiveBackend,
-    Backend, BlockRef, StorageResponse, StreamOfResults,
-    TransactionStatus,
 };
 use crate::config::{Config, HashFor};
 use crate::error::{BackendError, CombinedBackendError};
 use async_trait::async_trait;
-use futures::StreamExt;
-use subxt_rpcs::RpcClient;
 use futures::Stream;
+use futures::StreamExt;
 use std::task::Poll;
+use subxt_rpcs::RpcClient;
 
 pub struct CombinedBackendBuilder<T: Config> {
     archive: BackendChoice<ArchiveBackend<T>>,
@@ -33,7 +30,7 @@ enum BackendChoice<V> {
     UseDefault,
 }
 
-impl <T: Config> CombinedBackendBuilder<T> {
+impl<T: Config> CombinedBackendBuilder<T> {
     /// Create a new [`CombinedBackendBuilder`].
     pub fn new() -> Self {
         CombinedBackendBuilder {
@@ -86,7 +83,10 @@ impl <T: Config> CombinedBackendBuilder<T> {
     ///
     /// If you just want to run the driver in the background until completion in on the default runtime,
     /// use [`CombinedBackendBuilder::build_with_background_driver`] instead.
-    pub async fn build(self, rpc_client: impl Into<RpcClient>) -> Result<(CombinedBackend<T>, CombinedBackendDriver<T>), CombinedBackendError> {
+    pub async fn build(
+        self,
+        rpc_client: impl Into<RpcClient>,
+    ) -> Result<(CombinedBackend<T>, CombinedBackendDriver<T>), CombinedBackendError> {
         let rpc_client = rpc_client.into();
 
         // What does the thing wer're talking to actually know about?
@@ -98,7 +98,9 @@ impl <T: Config> CombinedBackendBuilder<T> {
         let has_archive_methods = methods.iter().any(|m| m.starts_with("archive_v1_"));
         let has_chainhead_methods = methods.iter().any(|m| m.starts_with("chainHead_v1"));
 
-        let mut combined_driver = CombinedBackendDriver { chainhead_driver: None };
+        let mut combined_driver = CombinedBackendDriver {
+            chainhead_driver: None,
+        };
 
         let archive = if has_archive_methods {
             match self.archive {
@@ -106,19 +108,24 @@ impl <T: Config> CombinedBackendBuilder<T> {
                 BackendChoice::UseDefault => Some(ArchiveBackend::new(rpc_client.clone())),
                 BackendChoice::DontUse => None,
             }
-        } else { None };
+        } else {
+            None
+        };
 
         let chainhead = if has_chainhead_methods {
             match self.chainhead {
                 BackendChoice::Use(b) => Some(b),
                 BackendChoice::UseDefault => {
-                    let (chainhead, chainhead_driver) = ChainHeadBackend::builder().build(rpc_client.clone());
+                    let (chainhead, chainhead_driver) =
+                        ChainHeadBackend::builder().build(rpc_client.clone());
                     combined_driver.chainhead_driver = Some(chainhead_driver);
                     Some(chainhead)
-                },
+                }
                 BackendChoice::DontUse => None,
             }
-        } else { None };
+        } else {
+            None
+        };
 
         let legacy = match self.legacy {
             BackendChoice::Use(b) => Some(b),
@@ -129,7 +136,7 @@ impl <T: Config> CombinedBackendBuilder<T> {
         let combined = CombinedBackend {
             archive,
             chainhead,
-            legacy
+            legacy,
         };
 
         Ok((combined, combined_driver))
@@ -141,10 +148,11 @@ impl <T: Config> CombinedBackendBuilder<T> {
     /// - On non-wasm targets, this will spawn the driver on `tokio`.
     /// - On wasm targets, this will spawn the driver on `wasm-bindgen-futures`.
     #[cfg(feature = "runtime")]
-    pub async fn build_with_background_driver(self, client: impl Into<RpcClient>) -> Result<CombinedBackend<T>, CombinedBackendError> {
+    pub async fn build_with_background_driver(
-        let (backend, mut driver) = self
+        self,
-            .build(client)
+        client: impl Into<RpcClient>,
-            .await?;
+    ) -> Result<CombinedBackend<T>, CombinedBackendError> {
+        let (backend, mut driver) = self.build(client).await?;
 
         super::utils::spawn(async move {
             // NOTE: we need to poll the driver until it's done i.e returns None
@@ -166,10 +174,10 @@ impl <T: Config> CombinedBackendBuilder<T> {
 /// that the [`CombinedBackend`] can make progress. It does not need polling
 /// if [`CombinedBackendDriver::needs_polling`] returns `false`.
 pub struct CombinedBackendDriver<T: Config> {
-    chainhead_driver: Option<ChainHeadBackendDriver<T>>
+    chainhead_driver: Option<ChainHeadBackendDriver<T>>,
 }
 
-impl <T: Config> CombinedBackendDriver<T> {
+impl<T: Config> CombinedBackendDriver<T> {
     pub fn needs_polling(&self) -> bool {
         self.chainhead_driver.is_some()
     }
@@ -183,7 +191,7 @@ impl<T: Config> Stream for CombinedBackendDriver<T> {
     ) -> std::task::Poll<Option<Self::Item>> {
         match &mut self.chainhead_driver {
             Some(driver) => driver.poll_next_unpin(cx),
-            None => Poll::Ready(None)
+            None => Poll::Ready(None),
         }
     }
 }
@@ -196,7 +204,7 @@ pub struct CombinedBackend<T: Config> {
     legacy: Option<LegacyBackend<T>>,
 }
 
-impl <T: Config> CombinedBackend<T> {
+impl<T: Config> CombinedBackend<T> {
     /// Configure and construct a [`CombinedBackend`].
     pub fn builder() -> CombinedBackendBuilder<T> {
         CombinedBackendBuilder::new()
@@ -243,13 +251,11 @@ impl<T: Config> Backend<T> for CombinedBackend<T> {
         keys: Vec<Vec<u8>>,
         at: HashFor<T>,
     ) -> Result<StreamOfResults<StorageResponse>, BackendError> {
-        try_backends(&[
+        try_backends(
-            self.archive(),
+            &[self.archive(), self.chainhead(), self.legacy()],
-            self.chainhead(),
+            async |b: &dyn Backend<T>| b.storage_fetch_values(keys.clone(), at).await,
-            self.legacy()
+        )
-        ], async |b: &dyn Backend<T>| {
+        .await
-            b.storage_fetch_values(keys.clone(), at).await
-        }).await
     }
 
     async fn storage_fetch_descendant_keys(
@@ -257,13 +263,11 @@ impl<T: Config> Backend<T> for CombinedBackend<T> {
         key: Vec<u8>,
         at: HashFor<T>,
     ) -> Result<StreamOfResults<Vec<u8>>, BackendError> {
-        try_backends(&[
+        try_backends(
-            self.archive(),
+            &[self.archive(), self.chainhead(), self.legacy()],
-            self.chainhead(),
+            async |b: &dyn Backend<T>| b.storage_fetch_descendant_keys(key.clone(), at).await,
-            self.legacy()
+        )
-        ], async |b: &dyn Backend<T>| {
+        .await
-            b.storage_fetch_descendant_keys(key.clone(), at).await
-        }).await
     }
 
     async fn storage_fetch_descendant_values(
@@ -271,123 +275,130 @@ impl<T: Config> Backend<T> for CombinedBackend<T> {
         key: Vec<u8>,
         at: HashFor<T>,
     ) -> Result<StreamOfResults<StorageResponse>, BackendError> {
-        try_backends(&[
+        try_backends(
-            self.archive(),
+            &[self.archive(), self.chainhead(), self.legacy()],
-            self.chainhead(),
+            async |b: &dyn Backend<T>| b.storage_fetch_descendant_values(key.clone(), at).await,
-            self.legacy()
+        )
-        ], async |b: &dyn Backend<T>| {
+        .await
-            b.storage_fetch_descendant_values(key.clone(), at).await
-        }).await
     }
 
     async fn genesis_hash(&self) -> Result<HashFor<T>, BackendError> {
-        try_backends(&[
+        try_backends(
-            self.archive(),
+            &[self.archive(), self.chainhead(), self.legacy()],
-            self.chainhead(),
+            async |b: &dyn Backend<T>| b.genesis_hash().await,
-            self.legacy()
+        )
-        ], async |b: &dyn Backend<T>| {
+        .await
-            b.genesis_hash().await
-        }).await
     }
 
-    async fn block_number_to_hash(&self, number: u64) -> Result<Option<BlockRef<HashFor<T>>>, BackendError> {
+    async fn block_number_to_hash(
-        try_backends(&[
+        &self,
-            self.archive(),
+        number: u64,
-            self.legacy(),
+    ) -> Result<Option<BlockRef<HashFor<T>>>, BackendError> {
-            // chainHead last as it cannot handle this request and will fail, so it's here
+        try_backends(
-            // just to hand back a more relevant error in case the above two backends aren't
+            &[
-            // enabled or have some issue.
+                self.archive(),
-            self.chainhead()
+                self.legacy(),
-        ], async |b: &dyn Backend<T>| {
+                // chainHead last as it cannot handle this request and will fail, so it's here
-            b.block_number_to_hash(number).await
+                // just to hand back a more relevant error in case the above two backends aren't
-        }).await
+                // enabled or have some issue.
+                self.chainhead(),
+            ],
+            async |b: &dyn Backend<T>| b.block_number_to_hash(number).await,
+        )
+        .await
     }
 
     async fn block_header(&self, at: HashFor<T>) -> Result<Option<T::Header>, BackendError> {
-        try_backends(&[
+        try_backends(
-            self.archive(),
+            &[self.archive(), self.chainhead(), self.legacy()],
-            self.chainhead(),
+            async |b: &dyn Backend<T>| b.block_header(at).await,
-            self.legacy()
+        )
-        ], async |b: &dyn Backend<T>| {
+        .await
-            b.block_header(at).await
-        }).await
     }
 
     async fn block_body(&self, at: HashFor<T>) -> Result<Option<Vec<Vec<u8>>>, BackendError> {
-        try_backends(&[
+        try_backends(
-            self.archive(),
+            &[self.archive(), self.chainhead(), self.legacy()],
-            self.chainhead(),
+            async |b: &dyn Backend<T>| b.block_body(at).await,
-            self.legacy()
+        )
-        ], async |b: &dyn Backend<T>| {
+        .await
-            b.block_body(at).await
-        }).await
     }
 
     async fn latest_finalized_block_ref(&self) -> Result<BlockRef<HashFor<T>>, BackendError> {
-        try_backends(&[
+        try_backends(
-            // Prioritize chainHead backend since it's streaming these things; save another call.
+            &[
-            self.chainhead(),
+                // Prioritize chainHead backend since it's streaming these things; save another call.
-            self.archive(),
+                self.chainhead(),
-            self.legacy()
+                self.archive(),
-        ], async |b: &dyn Backend<T>| {
+                self.legacy(),
-            b.latest_finalized_block_ref().await
+            ],
-        }).await
+            async |b: &dyn Backend<T>| b.latest_finalized_block_ref().await,
+        )
+        .await
     }
 
     async fn stream_all_block_headers(
         &self,
         hasher: T::Hasher,
     ) -> Result<StreamOfResults<(T::Header, BlockRef<HashFor<T>>)>, BackendError> {
-        try_backends(&[
+        try_backends(
-            // Ignore archive backend; it doesn't support this.
+            &[
-            self.chainhead(),
+                // Ignore archive backend; it doesn't support this.
-            self.legacy()
+                self.chainhead(),
-        ], async |b: &dyn Backend<T>| {
+                self.legacy(),
-            b.stream_all_block_headers(hasher.clone()).await
+            ],
-        }).await
+            async |b: &dyn Backend<T>| b.stream_all_block_headers(hasher.clone()).await,
+        )
+        .await
     }
 
     async fn stream_best_block_headers(
         &self,
         hasher: T::Hasher,
     ) -> Result<StreamOfResults<(T::Header, BlockRef<HashFor<T>>)>, BackendError> {
-        try_backends(&[
+        try_backends(
-            // Ignore archive backend; it doesn't support this.
+            &[
-            self.chainhead(),
+                // Ignore archive backend; it doesn't support this.
-            self.legacy()
+                self.chainhead(),
-        ], async |b: &dyn Backend<T>| {
+                self.legacy(),
-            b.stream_best_block_headers(hasher.clone()).await
+            ],
-        }).await
+            async |b: &dyn Backend<T>| b.stream_best_block_headers(hasher.clone()).await,
+        )
+        .await
     }
 
     async fn stream_finalized_block_headers(
         &self,
         hasher: T::Hasher,
     ) -> Result<StreamOfResults<(T::Header, BlockRef<HashFor<T>>)>, BackendError> {
-        try_backends(&[
+        try_backends(
-            // Ignore archive backend; it doesn't support this.
+            &[
-            self.chainhead(),
+                // Ignore archive backend; it doesn't support this.
-            self.legacy()
+                self.chainhead(),
-        ], async |b: &dyn Backend<T>| {
+                self.legacy(),
-            b.stream_finalized_block_headers(hasher.clone()).await
+            ],
-        }).await
+            async |b: &dyn Backend<T>| b.stream_finalized_block_headers(hasher.clone()).await,
+        )
+        .await
     }
 
     async fn submit_transaction(
         &self,
         extrinsic: &[u8],
     ) -> Result<StreamOfResults<TransactionStatus<HashFor<T>>>, BackendError> {
-        try_backends(&[
+        try_backends(
-            // chainHead first as it does the same as the archive backend, but with better
+            &[
-            // guarantees around the block handed back being pinned & ready to access.
+                // chainHead first as it does the same as the archive backend, but with better
-            self.chainhead(),
+                // guarantees around the block handed back being pinned & ready to access.
-            self.legacy(),
+                self.chainhead(),
-            // archive last just incase chainHead & legacy fail or aren't provided for some 
+                self.legacy(),
-            // reason.
+                // archive last just incase chainHead & legacy fail or aren't provided for some
-            self.archive(),
+                // reason.
-        ], async |b: &dyn Backend<T>| {
+                self.archive(),
-            b.submit_transaction(extrinsic).await
+            ],
-        }).await
+            async |b: &dyn Backend<T>| b.submit_transaction(extrinsic).await,
+        )
+        .await
     }
 
     async fn call(
@@ -396,20 +407,18 @@ impl<T: Config> Backend<T> for CombinedBackend<T> {
         call_parameters: Option<&[u8]>,
         at: HashFor<T>,
     ) -> Result<Vec<u8>, BackendError> {
-        try_backends(&[
+        try_backends(
-            self.archive(),
+            &[self.archive(), self.chainhead(), self.legacy()],
-            self.chainhead(),
+            async |b: &dyn Backend<T>| b.call(method, call_parameters, at).await,
-            self.legacy()
+        )
-        ], async |b: &dyn Backend<T>| {
+        .await
-            b.call(method, call_parameters, at).await
-        }).await
     }
 }
 
 /// Call one backend after the other in the list until we get a successful result back.
 async fn try_backends<'s, 'b, T, Func, Fut, O>(
     backends: &'s [Option<&'b dyn Backend<T>>],
-    mut f: Func
+    mut f: Func,
 ) -> Result<O, BackendError>
 where
     'b: 's,
@@ -417,13 +426,14 @@ where
     Func: FnMut(&'b dyn Backend<T>) -> Fut,
     Fut: Future<Output = Result<O, BackendError>> + 'b,
 {
-    static NO_AVAILABLE_BACKEND: &str = "None of the configured backends are capable of handling this request";
+    static NO_AVAILABLE_BACKEND: &str =
+        "None of the configured backends are capable of handling this request";
     let mut err = BackendError::other(NO_AVAILABLE_BACKEND);
 
     for backend in backends.into_iter().filter_map(|b| *b) {
         match f(backend).await {
             Ok(res) => return Ok(res),
-            Err(e) => { err = e }
+            Err(e) => err = e,
         }
     }
 

new/src/backend/legacy.rs

@@ -7,21 +7,20 @@
 
 mod descendant_streams;
 
-use subxt_rpcs::methods::legacy::{ TransactionStatus as RpcTransactionStatus, LegacyRpcMethods };
 use crate::backend::utils::{retry, retry_stream};
 use crate::backend::{
-    Backend, BlockRef, StorageResponse, StreamOf, StreamOfResults,
+    Backend, BlockRef, StorageResponse, StreamOf, StreamOfResults, TransactionStatus,
-    TransactionStatus,
 };
 use crate::config::{Config, HashFor, Hasher, Header, RpcConfigFor};
 use crate::error::BackendError;
 use async_trait::async_trait;
+use codec::Encode;
+use descendant_streams::{StorageFetchDescendantKeysStream, StorageFetchDescendantValuesStream};
 use futures::TryStreamExt;
 use futures::{Future, Stream, StreamExt, future, future::Either, stream};
 use subxt_rpcs::RpcClient;
 use subxt_rpcs::methods::legacy::NumberOrHex;
-use codec::Encode;
+use subxt_rpcs::methods::legacy::{LegacyRpcMethods, TransactionStatus as RpcTransactionStatus};
-use descendant_streams::{StorageFetchDescendantKeysStream, StorageFetchDescendantValuesStream};
 
 /// Configure and build an [`LegacyBackend`].
 pub struct LegacyBackendBuilder<T> {
@@ -135,7 +134,7 @@ impl<T: Config> Backend<T> for LegacyBackend<T> {
             self.methods.clone(),
             key,
             at,
-            self.storage_page_size
+            self.storage_page_size,
         );
 
         let keys = keys.flat_map(|keys| {
@@ -163,7 +162,7 @@ impl<T: Config> Backend<T> for LegacyBackend<T> {
             self.methods.clone(),
             key,
             at,
-            self.storage_page_size
+            self.storage_page_size,
         );
 
         Ok(StreamOf(Box::pin(values_stream)))
@@ -177,7 +176,10 @@ impl<T: Config> Backend<T> for LegacyBackend<T> {
         .await
     }
 
-    async fn block_number_to_hash(&self, number: u64) -> Result<Option<BlockRef<HashFor<T>>>, BackendError> {
+    async fn block_number_to_hash(
+        &self,
+        number: u64,
+    ) -> Result<Option<BlockRef<HashFor<T>>>, BackendError> {
         retry(|| async {
             let number_or_hash = NumberOrHex::Number(number);
             let hash = self
@@ -186,7 +188,8 @@ impl<T: Config> Backend<T> for LegacyBackend<T> {
                 .await?
                 .map(BlockRef::from_hash);
             Ok(hash)
-        }).await
+        })
+        .await
     }
 
     async fn block_header(&self, at: HashFor<T>) -> Result<Option<T::Header>, BackendError> {

new/src/backend/legacy/descendant_streams.rs

@@ -1,12 +1,12 @@
-use crate::backend::utils::retry;
+use super::LegacyRpcMethods;
 use crate::backend::StorageResponse;
+use crate::backend::utils::retry;
 use crate::config::{Config, HashFor, RpcConfigFor};
 use crate::error::BackendError;
 use futures::{Future, FutureExt, Stream, StreamExt};
 use std::collections::VecDeque;
 use std::pin::Pin;
 use std::task::{Context, Poll};
-use super::LegacyRpcMethods;
 
 /// This provides a stream of values given some prefix `key`. It
 /// internally manages pagination and such.
@@ -26,7 +26,7 @@ pub struct StorageFetchDescendantKeysStream<T: Config> {
     done: bool,
 }
 
-impl <T: Config> StorageFetchDescendantKeysStream<T> {
+impl<T: Config> StorageFetchDescendantKeysStream<T> {
     /// Fetch descendant keys.
     pub fn new(
         methods: LegacyRpcMethods<RpcConfigFor<T>>,
@@ -91,7 +91,7 @@ impl<T: Config> Stream for StorageFetchDescendantKeysStream<T> {
 
                         // Error getting keys? Return it.
                         return Poll::Ready(Some(Err(e)));
-                    },
+                    }
                     Poll::Pending => {
                         this.keys_fut = Some(keys_fut);
                         return Poll::Pending;
@@ -142,7 +142,7 @@ pub struct StorageFetchDescendantValuesStream<T: Config> {
     results: VecDeque<(Vec<u8>, Vec<u8>)>,
 }
 
-impl <T: Config> StorageFetchDescendantValuesStream<T> {
+impl<T: Config> StorageFetchDescendantValuesStream<T> {
     /// Fetch descendant values.
     pub fn new(
         methods: LegacyRpcMethods<RpcConfigFor<T>>,
@@ -201,7 +201,7 @@ impl<T: Config> Stream for StorageFetchDescendantValuesStream<T> {
                             continue;
                         }
 
-                        return Poll::Ready(Some(Err(e)))
+                        return Poll::Ready(Some(Err(e)));
                     }
                     Poll::Pending => {
                         this.results_fut = Some(results_fut);

new/src/backend/utils.rs

@@ -148,7 +148,7 @@ where
             match &mut self.state {
                 RetrySubscriptionState::Init => {
                     self.state = RetrySubscriptionState::Pending((self.resubscribe)());
-                },
+                }
                 RetrySubscriptionState::Stream(s) => match s.poll_next_unpin(cx) {
                     Poll::Ready(Some(Err(err))) => {
                         if err.is_disconnected_will_reconnect() {
@@ -158,7 +158,7 @@ where
                     }
                     Poll::Ready(None) => {
                         self.state = RetrySubscriptionState::Done;
-                        return Poll::Ready(None)
+                        return Poll::Ready(None);
                     }
                     Poll::Ready(Some(Ok(val))) => {
                         return Poll::Ready(Some(Ok(val)));
@@ -182,9 +182,7 @@ where
                         return Poll::Pending;
                     }
                 },
-                RetrySubscriptionState::Done => {
+                RetrySubscriptionState::Done => return Poll::Ready(None),
-                    return Poll::Ready(None)
-                }
             };
         }
     }

new/src/client.rs

@@ -1,15 +1,17 @@
 mod offline_client;
 mod online_client;
 
+use crate::config::{Config, HashFor};
 use core::marker::PhantomData;
+use subxt_metadata::Metadata;
 
 // We keep these traits internal, so that we can mess with them later if needed,
 // and instead only the concrete types are public which wrap these trait impls.
 pub(crate) use offline_client::OfflineClientAtBlockT;
 pub(crate) use online_client::OnlineClientAtBlockT;
 
-pub use offline_client::OfflineClient;
+pub use offline_client::{OfflineClient, OfflineClientAtBlock};
-pub use online_client::OnlineClient;
+pub use online_client::{OnlineClient, OnlineClientAtBlock};
 
 /// This represents a client at a specific block number.
 #[derive(Clone, Debug)]
@@ -27,3 +29,23 @@ impl<Client, T> ClientAtBlock<Client, T> {
         }
     }
 }
+
+impl<Client, T> ClientAtBlock<Client, T>
+where
+    T: Config,
+    Client: OfflineClientAtBlockT,
+{
+    pub fn metadata_ref(&self) -> &Metadata {
+        self.client.metadata_ref()
+    }
+}
+
+impl<Client, T> ClientAtBlock<Client, T>
+where
+    T: Config,
+    Client: OnlineClientAtBlockT<T>,
+{
+    pub fn block_hash(&self) -> HashFor<T> {
+        self.client.block_hash()
+    }
+}

new/src/client/offline_client.rs

@@ -1,8 +1,8 @@
-use crate::config::Config;
 use crate::client::ClientAtBlock;
+use crate::config::Config;
 use crate::error::OfflineClientAtBlockError;
-use subxt_metadata::Metadata;
 use std::sync::Arc;
+use subxt_metadata::Metadata;
 
 #[derive(Clone, Debug)]
 pub struct OfflineClient<T: Config> {
@@ -13,9 +13,7 @@ pub struct OfflineClient<T: Config> {
 impl<T: Config> OfflineClient<T> {
     /// Create a new [`OfflineClient`] with the given configuration.
     pub fn new(config: T) -> Self {
-        OfflineClient {
+        OfflineClient { config }
-            config,
-        }
     }
 
     /// Pick the block height at which to operate. This references data from the
@@ -35,25 +33,29 @@ impl<T: Config> OfflineClient<T> {
             .metadata_for_spec_version(spec_version)
             .ok_or(OfflineClientAtBlockError::MetadataNotFound { spec_version })?;
 
-        Ok(ClientAtBlock::new(OfflineClientAtBlock {
+        Ok(ClientAtBlock::new(OfflineClientAtBlock { metadata }))
-            metadata,
-        }))
     }
 }
 
+#[derive(Clone)]
 pub struct OfflineClientAtBlock {
     metadata: Arc<Metadata>,
 }
 
 /// This represents an offline-only client at a specific block.
 #[doc(hidden)]
-pub trait OfflineClientAtBlockT {
+pub trait OfflineClientAtBlockT: Clone {
-    /// Get the metadata appropriate for this block.
+    /// Get a reference to the metadata appropriate for this block.
-    fn metadata(&self) -> &Metadata;
+    fn metadata_ref(&self) -> &Metadata;
+    /// Get a clone of the metadata appropriate for this block.
+    fn metadata(&self) -> Arc<Metadata>;
 }
 
 impl OfflineClientAtBlockT for OfflineClientAtBlock {
-    fn metadata(&self) -> &Metadata {
+    fn metadata_ref(&self) -> &Metadata {
         &self.metadata
     }
+    fn metadata(&self) -> Arc<Metadata> {
+        self.metadata.clone()
+    }
 }

new/src/client/online_client.rs

@@ -1,17 +1,19 @@
 mod block_number_or_ref;
+mod blocks;
 
-use core::marker::PhantomData;
 use super::ClientAtBlock;
 use super::OfflineClientAtBlockT;
-use crate::config::{ Config, HashFor, Header, Hasher };
+use crate::backend::{Backend, BlockRef, CombinedBackend};
-use crate::error::OnlineClientAtBlockError;
+use crate::config::{Config, HashFor, Hasher, Header};
-use crate::backend::{ Backend, CombinedBackend, BlockRef };
+use crate::error::{BlocksError, OnlineClientAtBlockError};
+use blocks::Blocks;
 use codec::{Compact, Decode, Encode};
+use core::marker::PhantomData;
 use frame_metadata::{RuntimeMetadata, RuntimeMetadataPrefixed};
 use scale_info_legacy::TypeRegistrySet;
 use std::sync::Arc;
-use subxt_rpcs::RpcClient;
 use subxt_metadata::Metadata;
+use subxt_rpcs::RpcClient;
 
 #[cfg(feature = "jsonrpsee")]
 #[cfg_attr(docsrs, doc(cfg(feature = "jsonrpsee")))]
@@ -32,7 +34,7 @@ struct OnlineClientInner<T: Config> {
     backend: Arc<dyn Backend<T>>,
 }
 
-impl <T: Config> std::fmt::Debug for OnlineClientInner<T> {
+impl<T: Config> std::fmt::Debug for OnlineClientInner<T> {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.debug_struct("OnlineClientInner")
             .field("config", &"<config>")
@@ -63,9 +65,9 @@ impl<T: Config> OnlineClient<T> {
             url: url_str.to_string(),
         })?;
         if !Self::is_url_secure(&url) {
-            return Err(OnlineClientError::RpcError(
+            return Err(OnlineClientError::RpcError(subxt_rpcs::Error::InsecureUrl(
-                subxt_rpcs::Error::InsecureUrl(url_str.to_string()),
+                url_str.to_string(),
-            ));
+            )));
         }
         OnlineClient::from_insecure_url(config, url).await
     }
@@ -110,18 +112,98 @@ impl<T: Config> OnlineClient<T> {
 
     /// Construct a new [`OnlineClient`] by providing an underlying [`Backend`]
     /// implementation to power it.
-    pub fn from_backend(
+    pub fn from_backend(config: T, backend: impl Into<Arc<dyn Backend<T>>>) -> OnlineClient<T> {
-        config: T,
-        backend: impl Into<Arc<dyn Backend<T>>>,
-    ) -> OnlineClient<T> {
         OnlineClient {
             inner: Arc::new(OnlineClientInner {
                 config,
-                backend: backend.into()
+                backend: backend.into(),
-            })
+            }),
         }
     }
 
+    /// Obtain a stream of all blocks imported by the node.
+    ///
+    /// **Note:** You probably want to use [`Self::stream_blocks()`] most of
+    /// the time. Blocks returned here may be pruned at any time and become inaccessible,
+    /// leading to errors when trying to work with them.
+    pub async fn stream_all_blocks(&self) -> Result<Blocks<T>, BlocksError> {
+        // We need a hasher to know how to hash things. Thus, we need metadata to instantiate
+        // the hasher, so let's use the current block.
+        let current_block = self
+            .at_current_block()
+            .await
+            .map_err(BlocksError::CannotGetCurrentBlock)?;
+        let hasher = current_block.client.hasher.clone();
+
+        let stream = self
+            .inner
+            .backend
+            .stream_all_block_headers(hasher)
+            .await
+            .map_err(BlocksError::CannotGetBlockHeaderStream)?;
+
+        Ok(Blocks::from_headers_stream(self.clone(), stream))
+    }
+
+    /// Obtain a stream of blocks imported by the node onto the current best fork.
+    ///
+    /// **Note:** You probably want to use [`Self::stream_blocks()`] most of
+    /// the time. Blocks returned here may be pruned at any time and become inaccessible,
+    /// leading to errors when trying to work with them.
+    pub async fn stream_best_blocks(&self) -> Result<Blocks<T>, BlocksError> {
+        // We need a hasher to know how to hash things. Thus, we need metadata to instantiate
+        // the hasher, so let's use the current block.
+        let current_block = self
+            .at_current_block()
+            .await
+            .map_err(BlocksError::CannotGetCurrentBlock)?;
+        let hasher = current_block.client.hasher.clone();
+
+        let stream = self
+            .inner
+            .backend
+            .stream_best_block_headers(hasher)
+            .await
+            .map_err(BlocksError::CannotGetBlockHeaderStream)?;
+
+        Ok(Blocks::from_headers_stream(self.clone(), stream))
+    }
+
+    /// Obtain a stream of finalized blocks.
+    pub async fn stream_blocks(&self) -> Result<Blocks<T>, BlocksError> {
+        // We need a hasher to know how to hash things. Thus, we need metadata to instantiate
+        // the hasher, so let's use the current block.
+        let current_block = self
+            .at_current_block()
+            .await
+            .map_err(BlocksError::CannotGetCurrentBlock)?;
+        let hasher = current_block.client.hasher.clone();
+
+        let stream = self
+            .inner
+            .backend
+            .stream_finalized_block_headers(hasher)
+            .await
+            .map_err(BlocksError::CannotGetBlockHeaderStream)?;
+
+        Ok(Blocks::from_headers_stream(self.clone(), stream))
+    }
+
+    /// Instantiate a client to work at the current finalized block _at the time of instantiation_.
+    /// This does not track new blocks.
+    pub async fn at_current_block(
+        &self,
+    ) -> Result<ClientAtBlock<OnlineClientAtBlock<T>, T>, OnlineClientAtBlockError> {
+        let latest_block = self
+            .inner
+            .backend
+            .latest_finalized_block_ref()
+            .await
+            .map_err(|e| OnlineClientAtBlockError::CannotGetCurrentBlock { reason: e })?;
+
+        self.at_block(latest_block).await
+    }
+
     /// Instantiate a client for working at a specific block.
     pub async fn at_block(
         &self,
@@ -140,13 +222,13 @@ impl<T: Config> OnlineClient<T> {
                     .await
                     .map_err(|e| OnlineClientAtBlockError::CannotGetBlockHeader {
                         block_hash: block_hash.into(),
-                        reason: e
+                        reason: e,
                     })?
                     .ok_or(OnlineClientAtBlockError::BlockHeaderNotFound {
-                        block_hash: block_hash.into()
+                        block_hash: block_hash.into(),
                     })?;
                 (block_ref, block_header.number())
-            },
+            }
             BlockNumberOrRef::Number(block_num) => {
                 let block_ref = self
                     .inner
@@ -155,10 +237,10 @@ impl<T: Config> OnlineClient<T> {
                     .await
                     .map_err(|e| OnlineClientAtBlockError::CannotGetBlockHash {
                         block_number: block_num,
-                        reason: e 
+                        reason: e,
                     })?
                     .ok_or(OnlineClientAtBlockError::BlockNotFound {
-                        block_number: block_num
+                        block_number: block_num,
                     })?;
                 (block_ref, block_num)
             }
@@ -176,7 +258,7 @@ impl<T: Config> OnlineClient<T> {
                     .await
                     .map_err(|e| OnlineClientAtBlockError::CannotGetSpecVersion {
                         block_hash: block_hash.into(),
-                        reason: e 
+                        reason: e,
                     })?;
 
                 #[derive(codec::Decode)]
@@ -199,101 +281,107 @@ impl<T: Config> OnlineClient<T> {
         let metadata = match self.inner.config.metadata_for_spec_version(spec_version) {
             Some(metadata) => metadata,
             None => {
-                let metadata: Metadata = match get_metadata(&*self.inner.backend, block_hash).await? {
+                let metadata: Metadata =
-                    m @ RuntimeMetadata::V0(_) |
+                    match get_metadata(&*self.inner.backend, block_hash).await? {
-                    m @ RuntimeMetadata::V1(_) |
+                        m @ RuntimeMetadata::V0(_)
-                    m @ RuntimeMetadata::V2(_) |
+                        | m @ RuntimeMetadata::V1(_)
-                    m @ RuntimeMetadata::V3(_) |
+                        | m @ RuntimeMetadata::V2(_)
-                    m @ RuntimeMetadata::V4(_) |
+                        | m @ RuntimeMetadata::V3(_)
-                    m @ RuntimeMetadata::V5(_) |
+                        | m @ RuntimeMetadata::V4(_)
-                    m @ RuntimeMetadata::V6(_) |
+                        | m @ RuntimeMetadata::V5(_)
-                    m @ RuntimeMetadata::V7(_) => {
+                        | m @ RuntimeMetadata::V6(_)
-                        return Err(OnlineClientAtBlockError::UnsupportedMetadataVersion {
+                        | m @ RuntimeMetadata::V7(_) => {
-                            block_hash: block_hash.into(),
+                            return Err(OnlineClientAtBlockError::UnsupportedMetadataVersion {
-                            version: m.version()
-                        })
-                    },
-                    RuntimeMetadata::V8(m) => {
-                        let types = get_legacy_types(self, spec_version)?;
-                        Metadata::from_v8(&m, &types)
-                            .map_err(|e| OnlineClientAtBlockError::CannotConvertLegacyMetadata {
                                 block_hash: block_hash.into(),
-                                metadata_version: 8,
+                                version: m.version(),
-                                reason: e
+                            });
+                        }
+                        RuntimeMetadata::V8(m) => {
+                            let types = get_legacy_types(self, spec_version)?;
+                            Metadata::from_v8(&m, &types).map_err(|e| {
+                                OnlineClientAtBlockError::CannotConvertLegacyMetadata {
+                                    block_hash: block_hash.into(),
+                                    metadata_version: 8,
+                                    reason: e,
+                                }
                             })?
-                    },
+                        }
-                    RuntimeMetadata::V9(m) => {
+                        RuntimeMetadata::V9(m) => {
-                        let types = get_legacy_types(self, spec_version)?;
+                            let types = get_legacy_types(self, spec_version)?;
-                        Metadata::from_v9(&m, &types)
+                            Metadata::from_v9(&m, &types).map_err(|e| {
-                            .map_err(|e| OnlineClientAtBlockError::CannotConvertLegacyMetadata {
+                                OnlineClientAtBlockError::CannotConvertLegacyMetadata {
-                                block_hash: block_hash.into(),
+                                    block_hash: block_hash.into(),
-                                metadata_version: 9,
+                                    metadata_version: 9,
-                                reason: e
+                                    reason: e,
+                                }
                             })?
-                    },
+                        }
-                    RuntimeMetadata::V10(m) => {
+                        RuntimeMetadata::V10(m) => {
-                        let types = get_legacy_types(self, spec_version)?;
+                            let types = get_legacy_types(self, spec_version)?;
-                        Metadata::from_v10(&m, &types)
+                            Metadata::from_v10(&m, &types).map_err(|e| {
-                            .map_err(|e| OnlineClientAtBlockError::CannotConvertLegacyMetadata {
+                                OnlineClientAtBlockError::CannotConvertLegacyMetadata {
-                                block_hash: block_hash.into(),
+                                    block_hash: block_hash.into(),
-                                metadata_version: 10,
+                                    metadata_version: 10,
-                                reason: e
+                                    reason: e,
+                                }
                             })?
-                    },
+                        }
-                    RuntimeMetadata::V11(m) => {
+                        RuntimeMetadata::V11(m) => {
-                        let types = get_legacy_types(self, spec_version)?;
+                            let types = get_legacy_types(self, spec_version)?;
-                        Metadata::from_v11(&m, &types)
+                            Metadata::from_v11(&m, &types).map_err(|e| {
-                            .map_err(|e| OnlineClientAtBlockError::CannotConvertLegacyMetadata {
+                                OnlineClientAtBlockError::CannotConvertLegacyMetadata {
-                                block_hash: block_hash.into(),
+                                    block_hash: block_hash.into(),
-                                metadata_version: 11,
+                                    metadata_version: 11,
-                                reason: e
+                                    reason: e,
+                                }
                             })?
-                    },
+                        }
-                    RuntimeMetadata::V12(m) => {
+                        RuntimeMetadata::V12(m) => {
-                        let types = get_legacy_types(self, spec_version)?;
+                            let types = get_legacy_types(self, spec_version)?;
-                        Metadata::from_v12(&m, &types)
+                            Metadata::from_v12(&m, &types).map_err(|e| {
-                            .map_err(|e| OnlineClientAtBlockError::CannotConvertLegacyMetadata {
+                                OnlineClientAtBlockError::CannotConvertLegacyMetadata {
-                                block_hash: block_hash.into(),
+                                    block_hash: block_hash.into(),
-                                metadata_version: 12,
+                                    metadata_version: 12,
-                                reason: e
+                                    reason: e,
+                                }
                             })?
-                    },
+                        }
-                    RuntimeMetadata::V13(m) => {
+                        RuntimeMetadata::V13(m) => {
-                        let types = get_legacy_types(self, spec_version)?;
+                            let types = get_legacy_types(self, spec_version)?;
-                        Metadata::from_v13(&m, &types)
+                            Metadata::from_v13(&m, &types).map_err(|e| {
-                            .map_err(|e| OnlineClientAtBlockError::CannotConvertLegacyMetadata {
+                                OnlineClientAtBlockError::CannotConvertLegacyMetadata {
-                                block_hash: block_hash.into(),
+                                    block_hash: block_hash.into(),
-                                metadata_version: 13,
+                                    metadata_version: 13,
-                                reason: e
+                                    reason: e,
+                                }
                             })?
-                    },
+                        }
-                    RuntimeMetadata::V14(m) => {
+                        RuntimeMetadata::V14(m) => Metadata::from_v14(m).map_err(|e| {
-                        Metadata::from_v14(m)
+                            OnlineClientAtBlockError::CannotConvertModernMetadata {
-                            .map_err(|e| OnlineClientAtBlockError::CannotConvertModernMetadata {
                                 block_hash: block_hash.into(),
                                 metadata_version: 14,
-                                reason: e
+                                reason: e,
-                            })?
+                            }
-                    },
+                        })?,
-                    RuntimeMetadata::V15(m) => {
+                        RuntimeMetadata::V15(m) => Metadata::from_v15(m).map_err(|e| {
-                        Metadata::from_v15(m)
+                            OnlineClientAtBlockError::CannotConvertModernMetadata {
-                            .map_err(|e| OnlineClientAtBlockError::CannotConvertModernMetadata {
                                 block_hash: block_hash.into(),
                                 metadata_version: 15,
-                                reason: e
+                                reason: e,
-                            })?
+                            }
-                    },
+                        })?,
-                    RuntimeMetadata::V16(m) => {
+                        RuntimeMetadata::V16(m) => Metadata::from_v16(m).map_err(|e| {
-                        Metadata::from_v16(m)
+                            OnlineClientAtBlockError::CannotConvertModernMetadata {
-                            .map_err(|e| OnlineClientAtBlockError::CannotConvertModernMetadata {
                                 block_hash: block_hash.into(),
                                 metadata_version: 16,
-                                reason: e
+                                reason: e,
-                            })?
+                            }
-                    },
+                        })?,
-                };
+                    };
                 let metadata = Arc::new(metadata);
-                self.inner.config.set_metadata_for_spec_version(spec_version, metadata.clone());
+                self.inner
+                    .config
+                    .set_metadata_for_spec_version(spec_version, metadata.clone());
                 metadata
             }
         };
@@ -307,15 +395,14 @@ impl<T: Config> OnlineClient<T> {
 
         Ok(ClientAtBlock {
             client: online_client_at_block,
-            marker: PhantomData 
+            marker: PhantomData,
         })
     }
 }
 
 /// This represents an online client at a specific block.
 #[doc(hidden)]
-pub trait OnlineClientAtBlockT<T: Config>: OfflineClientAtBlockT
+pub trait OnlineClientAtBlockT<T: Config>: OfflineClientAtBlockT {
-{
     /// Return the RPC methods we'll use to interact with the node.
     fn backend(&self) -> &dyn Backend<T>;
     /// Return the block hash for the current block.
@@ -325,6 +412,7 @@ pub trait OnlineClientAtBlockT<T: Config>: OfflineClientAtBlockT
 }
 
 /// The inner type providing the necessary data to work online at a specific block.
+#[derive(Clone)]
 pub struct OnlineClientAtBlock<T: Config> {
     metadata: Arc<Metadata>,
     backend: Arc<dyn Backend<T>>,
@@ -345,12 +433,18 @@ impl<T: Config> OnlineClientAtBlockT<T> for OnlineClientAtBlock<T> {
 }
 
 impl<T: Config> OfflineClientAtBlockT for OnlineClientAtBlock<T> {
-    fn metadata(&self) -> &Metadata {
+    fn metadata_ref(&self) -> &Metadata {
         &self.metadata
     }
+    fn metadata(&self) -> Arc<Metadata> {
+        self.metadata.clone()
+    }
 }
 
-fn get_legacy_types<T: Config>(client: &OnlineClient<T>, spec_version: u32) -> Result<TypeRegistrySet<'_>, OnlineClientAtBlockError> {
+fn get_legacy_types<T: Config>(
+    client: &OnlineClient<T>,
+    spec_version: u32,
+) -> Result<TypeRegistrySet<'_>, OnlineClientAtBlockError> {
     client
         .inner
         .config
@@ -377,7 +471,11 @@ async fn get_metadata<T: Config>(
     if let Some(version_to_get) = version_to_get {
         let version_bytes = version_to_get.encode();
         let rpc_response = backend
-            .call("Metadata_metadata_at_version", Some(&version_bytes), block_hash)
+            .call(
+                "Metadata_metadata_at_version",
+                Some(&version_bytes),
+                block_hash,
+            )
             .await
             .map_err(|e| OnlineClientAtBlockError::CannotGetMetadata {
                 block_hash: block_hash.into(),

new/src/client/online_client/block_number_or_ref.rs

@@ -1,5 +1,5 @@
-use crate::config::{ Config, HashFor, Hasher };
 use crate::backend::BlockRef;
+use crate::config::{Config, HashFor, Hasher};
 
 /// This represents either a block number or a reference
 /// to a block, which is essentially a block hash.
@@ -7,22 +7,22 @@ pub enum BlockNumberOrRef<T: Config> {
     /// A block number.
     Number(u64),
     /// A block ref / hash.
-    BlockRef(BlockRef<HashFor<T>>)
+    BlockRef(BlockRef<HashFor<T>>),
 }
 
-impl <T: Config> From<u32> for BlockNumberOrRef<T> {
+impl<T: Config> From<u32> for BlockNumberOrRef<T> {
     fn from(value: u32) -> Self {
         BlockNumberOrRef::Number(value.into())
     }
 }
 
-impl <T: Config> From<u64> for BlockNumberOrRef<T> {
+impl<T: Config> From<u64> for BlockNumberOrRef<T> {
     fn from(value: u64) -> Self {
         BlockNumberOrRef::Number(value)
     }
 }
 
-impl <T: Config> From<BlockRef<HashFor<T>>> for BlockNumberOrRef<T> {
+impl<T: Config> From<BlockRef<HashFor<T>>> for BlockNumberOrRef<T> {
     fn from(block_ref: BlockRef<HashFor<T>>) -> Self {
         BlockNumberOrRef::BlockRef(block_ref)
     }
@@ -31,9 +31,9 @@ impl <T: Config> From<BlockRef<HashFor<T>>> for BlockNumberOrRef<T> {
 // Ideally we'd have `impl From<HashFor<T>> for BlockNumberOrRef<T>` but since our config
 // could set _any_ hash type, this boils down to `impl From<H> for ..` which is too general.
 // Thus, we target our current concrete hash type.
-impl <T: Config> From<crate::config::substrate::H256> for BlockNumberOrRef<T> 
+impl<T: Config> From<crate::config::substrate::H256> for BlockNumberOrRef<T>
 where
-    <T::Hasher as Hasher>::Hash: From<crate::config::substrate::H256>
+    <T::Hasher as Hasher>::Hash: From<crate::config::substrate::H256>,
 {
     fn from(hash: crate::config::substrate::H256) -> Self {
         BlockNumberOrRef::BlockRef(BlockRef::from_hash(hash.into()))

new/src/client/online_client/blocks.rs

@@ -0,0 +1,76 @@
+use crate::backend::{BlockRef, StreamOfResults};
+use crate::client::{ClientAtBlock, OnlineClient, OnlineClientAtBlock};
+use crate::config::{Config, HashFor, Header};
+use crate::error::{BlocksError, OnlineClientAtBlockError};
+use futures::{Stream, StreamExt};
+use std::pin::Pin;
+use std::task::{Context, Poll};
+
+/// A stream of blocks.
+pub struct Blocks<T: Config> {
+    client: OnlineClient<T>,
+    stream: StreamOfResults<(T::Header, BlockRef<HashFor<T>>)>,
+}
+
+impl<T: Config> Blocks<T> {
+    pub(crate) fn from_headers_stream(
+        client: OnlineClient<T>,
+        stream: StreamOfResults<(T::Header, BlockRef<HashFor<T>>)>,
+    ) -> Self {
+        Blocks { client, stream }
+    }
+}
+
+impl<T: Config> Stream for Blocks<T> {
+    type Item = Result<Block<T>, BlocksError>;
+
+    fn poll_next(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Option<Self::Item>> {
+        let item = match self.stream.poll_next_unpin(cx) {
+            Poll::Pending => return Poll::Pending,
+            Poll::Ready(None) => return Poll::Ready(None),
+            Poll::Ready(Some(item)) => item,
+        };
+
+        let res = match item {
+            Ok((block_header, block_ref)) => Ok(Block {
+                block_ref,
+                block_header,
+                client: self.client.clone(),
+            }),
+            Err(e) => Err(BlocksError::CannotGetBlockHeader(e)),
+        };
+
+        Poll::Ready(Some(res))
+    }
+}
+
+/// A block from the stream of blocks.
+pub struct Block<T: Config> {
+    block_ref: BlockRef<HashFor<T>>,
+    block_header: T::Header,
+    client: OnlineClient<T>,
+}
+
+impl<T: Config> Block<T> {
+    /// The block hash
+    pub fn hash(&self) -> HashFor<T> {
+        self.block_ref.hash()
+    }
+
+    /// The block number.
+    pub fn number(&self) -> u64 {
+        self.block_header.number()
+    }
+
+    /// The block header.
+    pub fn header(&self) -> &T::Header {
+        &self.block_header
+    }
+
+    /// Instantiate a client at this block.
+    pub async fn client(
+        &self,
+    ) -> Result<ClientAtBlock<OnlineClientAtBlock<T>, T>, OnlineClientAtBlockError> {
+        self.client.at_block(self.block_ref.clone()).await
+    }
+}

new/src/config.rs

@@ -19,10 +19,10 @@ use codec::{Decode, Encode};
 use core::fmt::Debug;
 use scale_decode::DecodeAsType;
 use scale_encode::EncodeAsType;
-use serde::{Serialize, de::DeserializeOwned};
-use subxt_metadata::Metadata;
-use std::{fmt::Display, marker::PhantomData, sync::Arc};
 use scale_info_legacy::TypeRegistrySet;
+use serde::{Serialize, de::DeserializeOwned};
+use std::{fmt::Display, marker::PhantomData, sync::Arc};
+use subxt_metadata::Metadata;
 use subxt_rpcs::RpcConfig;
 
 pub use default_extrinsic_params::{DefaultExtrinsicParams, DefaultExtrinsicParamsBuilder};
@@ -72,21 +72,14 @@ pub trait Config: Clone + Debug + Sized + Send + Sync + 'static {
     /// The [`crate::client::OnlineClient`] will look this up on chain if it's not available here, and then
     /// call [`Config::set_metadata_for_spec_version`] to give the configuration the opportunity to cache it.
     /// The [`crate::client::OfflineClient`] will error if this is not available for the required spec version.
-    fn metadata_for_spec_version(
+    fn metadata_for_spec_version(&self, _spec_version: u32) -> Option<Arc<Metadata>> {
-        &self,
-        _spec_version: u32,
-    ) -> Option<Arc<Metadata>> {
         None
     }
 
     /// Set some metadata for a given spec version. the [`crate::client::OnlineClient`] will call this if it has
     /// to retrieve metadata from the chain, to give this the opportunity to cache it. The configuration can
     /// do nothing if it prefers.
-    fn set_metadata_for_spec_version(
+    fn set_metadata_for_spec_version(&self, _spec_version: u32, _metadata: Arc<Metadata>) {}
-        &self,
-        _spec_version: u32,
-        _metadata: Arc<Metadata>,
-    ) {}
 
     /// Return legacy types (ie types to use with Runtimes that return pre-V14 metadata) for a given spec version.
     /// If this returns `None`, [`subxt`] will return an error if type definitions are needed to access some older
@@ -105,10 +98,10 @@ pub trait Config: Clone + Debug + Sized + Send + Sync + 'static {
 /// `RpcConfigFor<Config>` can be used anywhere which requires an implementation of [`subxt_rpcs::RpcConfig`].
 /// This is only needed at the type level, and so there is no way to construct this.
 pub struct RpcConfigFor<T> {
-    marker: PhantomData<T>
+    marker: PhantomData<T>,
 }
 
-impl <T: Config> RpcConfig for RpcConfigFor<T> {
+impl<T: Config> RpcConfig for RpcConfigFor<T> {
     type Hash = HashFor<T>;
     type Header = T::Header;
     type AccountId = T::AccountId;

new/src/config/extrinsic_params.rs

@@ -11,9 +11,9 @@ use crate::{
     config::{Config, HashFor},
     error::ExtrinsicParamsError,
 };
-use subxt_metadata::Metadata;
-use std::sync::Arc;
 use core::any::Any;
+use std::sync::Arc;
+use subxt_metadata::Metadata;
 
 /// This provides access to some relevant client state in transaction extensions,
 /// and is just a combination of some of the available properties.

new/src/config/polkadot.rs

@@ -7,11 +7,11 @@
 use super::{Config, DefaultExtrinsicParams, DefaultExtrinsicParamsBuilder};
 
 use crate::config::substrate::{SubstrateConfig, SubstrateConfigBuilder};
-use std::sync::Arc;
 use scale_info_legacy::TypeRegistrySet;
+use std::sync::Arc;
 use subxt_metadata::Metadata;
 
-pub use crate::config::substrate::{ SpecVersionForRange, SubstrateHeader };
+pub use crate::config::substrate::{SpecVersionForRange, SubstrateHeader};
 pub use crate::utils::{AccountId32, MultiAddress, MultiSignature};
 pub use primitive_types::{H256, U256};
 
@@ -79,18 +79,11 @@ impl Config for PolkadotConfig {
         self.0.spec_version_for_block_number(block_number)
     }
 
-    fn metadata_for_spec_version(
+    fn metadata_for_spec_version(&self, spec_version: u32) -> Option<Arc<Metadata>> {
-        &self,
-        spec_version: u32,
-    ) -> Option<Arc<Metadata>> {
         self.0.metadata_for_spec_version(spec_version)
     }
 
-    fn set_metadata_for_spec_version(
+    fn set_metadata_for_spec_version(&self, spec_version: u32, metadata: Arc<Metadata>) {
-        &self,
-        spec_version: u32,
-        metadata: Arc<Metadata>,
-    ) {
         self.0.set_metadata_for_spec_version(spec_version, metadata)
     }
 }

new/src/config/substrate.rs

@@ -6,16 +6,16 @@
 
 use super::{Config, DefaultExtrinsicParams, DefaultExtrinsicParamsBuilder, Hasher, Header};
 use crate::config::Hash;
+use crate::utils::RangeMap;
 pub use crate::utils::{AccountId32, MultiAddress, MultiSignature};
 use codec::{Decode, Encode};
 pub use primitive_types::{H256, U256};
-use serde::{Deserialize, Serialize};
-use subxt_metadata::Metadata;
-use crate::utils::RangeMap;
 use scale_info_legacy::{ChainTypeRegistry, TypeRegistrySet};
+use serde::{Deserialize, Serialize};
 use std::collections::HashMap;
 use std::sync::Arc;
 use std::sync::Mutex;
+use subxt_metadata::Metadata;
 
 /// Construct a [`SubstrateConfig`] using this.
 pub struct SubstrateConfigBuilder {
@@ -81,10 +81,7 @@ impl SubstrateConfigBuilder {
 
     /// The storage hasher encoding/decoding changed during V9 metadata. By default we support the "new" version
     /// of things. We can use this option to support the old version of things prior to a given spec version.
-    pub fn use_old_v9_hashers_before_spec_version(
+    pub fn use_old_v9_hashers_before_spec_version(mut self, spec_version: u32) -> Self {
-        mut self,
-        spec_version: u32
-    ) -> Self {
         self.use_old_v9_hashers_before_spec_version = spec_version;
         self
     }
@@ -96,7 +93,7 @@ impl SubstrateConfigBuilder {
                 legacy_types: self.legacy_types,
                 spec_version_for_block_number: self.spec_version_for_block_number,
                 metadata_for_spec_version: self.metadata_for_spec_version,
-            })
+            }),
         }
     }
 }
@@ -116,7 +113,7 @@ pub struct SpecVersionForRange {
 /// that have not customized the block hash type).
 #[derive(Debug, Clone)]
 pub struct SubstrateConfig {
-    inner: Arc<SubstrateConfigInner>
+    inner: Arc<SubstrateConfigInner>,
 }
 
 #[derive(Debug)]
@@ -150,15 +147,13 @@ impl Config for SubstrateConfig {
     }
 
     fn spec_version_for_block_number(&self, block_number: u64) -> Option<u32> {
-        self.inner.spec_version_for_block_number
+        self.inner
+            .spec_version_for_block_number
             .get(block_number)
             .copied()
     }
 
-    fn metadata_for_spec_version(
+    fn metadata_for_spec_version(&self, spec_version: u32) -> Option<Arc<Metadata>> {
-        &self,
-        spec_version: u32,
-    ) -> Option<Arc<Metadata>> {
         self.inner
             .metadata_for_spec_version
             .lock()
@@ -167,11 +162,7 @@ impl Config for SubstrateConfig {
             .cloned()
     }
 
-    fn set_metadata_for_spec_version(
+    fn set_metadata_for_spec_version(&self, spec_version: u32, metadata: Arc<Metadata>) {
-        &self,
-        spec_version: u32,
-        metadata: Arc<Metadata>,
-    ) {
         self.inner
             .metadata_for_spec_version
             .lock()

new/src/config/transaction_extensions.rs

@@ -7,7 +7,7 @@
 //! [`AnyOf`] to configure the set of transaction extensions which are known about
 //! when interacting with a chain.
 
-use super::extrinsic_params::{ ExtrinsicParams, ClientState };
+use super::extrinsic_params::{ClientState, ExtrinsicParams};
 use crate::config::ExtrinsicParamsEncoder;
 use crate::config::{Config, HashFor};
 use crate::error::ExtrinsicParamsError;
@@ -16,9 +16,9 @@ use codec::{Compact, Encode};
 use core::any::Any;
 use core::fmt::Debug;
 use derive_where::derive_where;
-use std::collections::HashMap;
 use scale_decode::DecodeAsType;
 use scale_info::PortableRegistry;
+use std::collections::HashMap;
 
 // Re-export this here; it's a bit generically named to be re-exported from ::config.
 pub use super::extrinsic_params::Params;

new/src/error.rs

@@ -7,8 +7,8 @@
 mod dispatch_error;
 mod hex;
 
-use thiserror::Error as DeriveError;
 use std::borrow::Cow;
+use thiserror::Error as DeriveError;
 
 #[cfg(feature = "unstable-light-client")]
 pub use subxt_lightclient::LightClientError;
@@ -19,10 +19,10 @@ pub use dispatch_error::{
 };
 
 // Re-expose the errors we use from other crates here:
-pub use subxt_metadata::Metadata;
 pub use hex::Hex;
 pub use scale_decode::Error as DecodeError;
 pub use scale_encode::Error as EncodeError;
+pub use subxt_metadata::Metadata;
 pub use subxt_metadata::TryFromError as MetadataTryFromError;
 
 /// A global error type. Any of the errors exposed here can convert into this
@@ -50,14 +50,10 @@ pub enum Error {
     #[error(transparent)]
     BackendError(#[from] BackendError),
     #[error(transparent)]
-    BlockError(#[from] BlockError),
+    BlocksError(#[from] BlocksError),
     #[error(transparent)]
     AccountNonceError(#[from] AccountNonceError),
     #[error(transparent)]
-    RuntimeUpdaterError(#[from] RuntimeUpdaterError),
-    #[error(transparent)]
-    RuntimeUpdateeApplyError(#[from] RuntimeUpdateeApplyError),
-    #[error(transparent)]
     RuntimeApiError(#[from] RuntimeApiError),
     #[error(transparent)]
     EventsError(#[from] EventsError),
@@ -143,10 +139,12 @@ impl Error {
 
     fn backend_error(&self) -> Option<&BackendError> {
         match self {
-            Error::BlockError(e) => e.backend_error(),
+            // Many of these contain no backend error, but keep the checks next to
+            // the actual error types to make it harder to miss adding any, and be exhaustive
+            // here so new error variants are not missed as easily.
+            Error::BlocksError(e) => e.backend_error(),
             Error::AccountNonceError(e) => e.backend_error(),
             Error::OnlineClientError(e) => e.backend_error(),
-            Error::RuntimeUpdaterError(e) => e.backend_error(),
             Error::RuntimeApiError(e) => e.backend_error(),
             Error::EventsError(e) => e.backend_error(),
             Error::ExtrinsicError(e) => e.backend_error(),
@@ -155,8 +153,23 @@ impl Error {
             Error::TransactionEventsError(e) => e.backend_error(),
             Error::TransactionFinalizedSuccessError(e) => e.backend_error(),
             Error::StorageError(e) => e.backend_error(),
-            // Any errors that **don't** return a BackendError anywhere will return None:
+            Error::OfflineClientAtBlockError(e) => e.backend_error(),
-            _ => None,
+            Error::OnlineClientAtBlockError(e) => e.backend_error(),
+            Error::ExtrinsicDecodeErrorAt(e) => e.backend_error(),
+            Error::ConstantError(e) => e.backend_error(),
+            Error::CustomValueError(e) => e.backend_error(),
+            Error::StorageKeyError(e) => e.backend_error(),
+            Error::StorageValueError(e) => e.backend_error(),
+            Error::TransactionStatusError(e) => e.backend_error(),
+            Error::ModuleErrorDetailsError(e) => e.backend_error(),
+            Error::ModuleErrorDecodeError(e) => e.backend_error(),
+            Error::DispatchErrorDecodeError(e) => e.backend_error(),
+            // BackendError is always a BackendError:
+            Error::BackendError(e) => Some(e),
+            // Other errors come from different crates so can never contain a BackendError:
+            Error::OtherRpcClientError(_) => None,
+            Error::OtherCodecError(_) => None,
+            Error::Other(_) => None,
         }
     }
 }
@@ -182,6 +195,12 @@ pub enum OfflineClientAtBlockError {
     },
 }
 
+impl OfflineClientAtBlockError {
+    fn backend_error(&self) -> Option<&BackendError> {
+        None
+    }
+}
+
 #[derive(Debug, thiserror::Error)]
 #[non_exhaustive]
 #[allow(missing_docs)]
@@ -219,11 +238,39 @@ impl OnlineClientError {
     }
 }
 
+/// Errors constructing streams of blocks.
+#[allow(missing_docs)]
+#[derive(Debug, thiserror::Error)]
+#[non_exhaustive]
+pub enum BlocksError {
+    #[error("Cannot construct block stream: cannot get the current block: {0}")]
+    CannotGetCurrentBlock(OnlineClientAtBlockError),
+    #[error("Cannot construct block stream: cannot get block header stream: {0}")]
+    CannotGetBlockHeaderStream(BackendError),
+    #[error("Error streaming blocks: cannot get the next block header: {0}")]
+    CannotGetBlockHeader(BackendError),
+}
+
+impl BlocksError {
+    fn backend_error(&self) -> Option<&BackendError> {
+        match self {
+            BlocksError::CannotGetCurrentBlock(e) => e.backend_error(),
+            BlocksError::CannotGetBlockHeaderStream(e) => Some(e),
+            BlocksError::CannotGetBlockHeader(e) => Some(e),
+        }
+    }
+}
+
 /// Errors constructing an online client at a specific block number.
 #[allow(missing_docs)]
 #[derive(Debug, thiserror::Error)]
 #[non_exhaustive]
 pub enum OnlineClientAtBlockError {
+    #[error("Cannot construct OnlineClientAtBlock: cannot get the current block: {reason}")]
+    CannotGetCurrentBlock {
+        /// The error we encountered.
+        reason: BackendError,
+    },
     #[error(
         "Cannot construct OnlineClientAtBlock: failed to get block hash from node for block {block_number}: {reason}"
     )]
@@ -238,19 +285,25 @@ pub enum OnlineClientAtBlockError {
         /// The block number for which a block was not found.
         block_number: u64,
     },
-    #[error("Cannot construct OnlineClientAtBlock: cannot get the block header for block {block_hash}: {reason}")]
+    #[error(
+        "Cannot construct OnlineClientAtBlock: cannot get the block header for block {block_hash}: {reason}"
+    )]
     CannotGetBlockHeader {
         /// Block hash that we failed to fetch the header for.
         block_hash: Hex,
         /// The error we encountered.
         reason: BackendError,
     },
-    #[error("Cannot construct OnlineClientAtBlock: cannot find the block header for block {block_hash}")]
+    #[error(
+        "Cannot construct OnlineClientAtBlock: cannot find the block header for block {block_hash}"
+    )]
     BlockHeaderNotFound {
         /// Block hash that we failed to find the header for.
         block_hash: Hex,
     },
-    #[error("Cannot construct OnlineClientAtBlock: failed to obtain spec version for block {block_hash}: {reason}")]
+    #[error(
+        "Cannot construct OnlineClientAtBlock: failed to obtain spec version for block {block_hash}: {reason}"
+    )]
     CannotGetSpecVersion {
         /// The block hash for which we failed to obtain the spec version.
         block_hash: Hex,
@@ -275,41 +328,59 @@ pub enum OnlineClientAtBlockError {
         /// The error we encountered.
         reason: String,
     },
-    #[error("Cannot construct OnlineClientAtBlock: Metadata V{version} (required at block {block_hash} is not supported.")]
+    #[error(
+        "Cannot construct OnlineClientAtBlock: Metadata V{version} (required at block {block_hash} is not supported."
+    )]
     UnsupportedMetadataVersion {
         /// The block hash that requires the unsupported version.
         block_hash: Hex,
         /// The unsupported metadata version.
         version: u32,
     },
-    #[error("Cannot construct OnlineClientAtBlock: No legacy types were provided but we're trying to access a block that requires them.")]
+    #[error(
+        "Cannot construct OnlineClientAtBlock: No legacy types were provided but we're trying to access a block that requires them."
+    )]
     MissingLegacyTypes,
-    #[error("Cannot construct OnlineClientAtBlock: unable to convert legacy metadata (required at block {block_hash}): {reason}")]
+    #[error(
+        "Cannot construct OnlineClientAtBlock: unable to convert legacy metadata (required at block {block_hash}): {reason}"
+    )]
     CannotConvertLegacyMetadata {
         /// The block hash that requires legacy types.
         block_hash: Hex,
         /// The metadata version.
         metadata_version: u32,
         /// Reason the conversion failed.
-        reason: subxt_metadata::LegacyFromError
+        reason: subxt_metadata::LegacyFromError,
     },
-    #[error("Cannot construct OnlineClientAtBlock: unable to convert modern metadata (required at block {block_hash}): {reason}")]
+    #[error(
+        "Cannot construct OnlineClientAtBlock: unable to convert modern metadata (required at block {block_hash}): {reason}"
+    )]
     CannotConvertModernMetadata {
         /// The block hash that requires legacy types.
         block_hash: Hex,
         /// The metadata version.
         metadata_version: u32,
         /// Reason the conversion failed.
-        reason: subxt_metadata::TryFromError
+        reason: subxt_metadata::TryFromError,
-    }
+    }, // #[error(
+       //     "Cannot construct OnlineClientAtBlock: cannot inject types from metadata: failure to parse a type found in the metadata: {parse_error}"
+       // )]
+       // CannotInjectMetadataTypes {
+       //     /// Error parsing a type found in the metadata.
+       //     parse_error: scale_info_legacy::lookup_name::ParseError,
+       // },
+}
 
-    // #[error(
+impl OnlineClientAtBlockError {
-    //     "Cannot construct OnlineClientAtBlock: cannot inject types from metadata: failure to parse a type found in the metadata: {parse_error}"
+    fn backend_error(&self) -> Option<&BackendError> {
-    // )]
+        match self {
-    // CannotInjectMetadataTypes {
+            OnlineClientAtBlockError::CannotGetCurrentBlock { reason }
-    //     /// Error parsing a type found in the metadata.
+            | OnlineClientAtBlockError::CannotGetBlockHash { reason, .. }
-    //     parse_error: scale_info_legacy::lookup_name::ParseError,
+            | OnlineClientAtBlockError::CannotGetBlockHeader { reason, .. }
-    // },
+            | OnlineClientAtBlockError::CannotGetSpecVersion { reason, .. } => Some(reason),
+            _ => None,
+        }
+    }
 }
 
 #[derive(Debug, thiserror::Error)]
@@ -362,7 +433,7 @@ impl From<subxt_rpcs::Error> for BackendError {
 #[allow(missing_docs)]
 pub enum CombinedBackendError {
     #[error("Could not obtain the list of RPC methods to determine which backends can be used")]
-    CouldNotObtainRpcMethodList(subxt_rpcs::Error)
+    CouldNotObtainRpcMethodList(subxt_rpcs::Error),
 }
 
 /// An RPC error. Since we are generic over the RPC client that is used,
@@ -382,49 +453,6 @@ pub enum RpcError {
     SubscriptionDropped,
 }
 
-/// Block error
-#[derive(Debug, thiserror::Error)]
-#[non_exhaustive]
-#[allow(missing_docs)]
-pub enum BlockError {
-    #[error(
-        "Could not find the block body with hash {block_hash} (perhaps it was on a non-finalized fork?)"
-    )]
-    BlockNotFound { block_hash: Hex },
-    #[error("Could not download the block header with hash {block_hash}: {reason}")]
-    CouldNotGetBlockHeader {
-        block_hash: Hex,
-        reason: BackendError,
-    },
-    #[error("Could not download the latest block header: {0}")]
-    CouldNotGetLatestBlock(BackendError),
-    #[error("Could not subscribe to all blocks: {0}")]
-    CouldNotSubscribeToAllBlocks(BackendError),
-    #[error("Could not subscribe to best blocks: {0}")]
-    CouldNotSubscribeToBestBlocks(BackendError),
-    #[error("Could not subscribe to finalized blocks: {0}")]
-    CouldNotSubscribeToFinalizedBlocks(BackendError),
-    #[error("Error getting account nonce at block {block_hash}")]
-    AccountNonceError {
-        block_hash: Hex,
-        account_id: Hex,
-        reason: AccountNonceError,
-    },
-}
-
-impl BlockError {
-    fn backend_error(&self) -> Option<&BackendError> {
-        match self {
-            BlockError::CouldNotGetBlockHeader { reason: e, .. }
-            | BlockError::CouldNotGetLatestBlock(e)
-            | BlockError::CouldNotSubscribeToAllBlocks(e)
-            | BlockError::CouldNotSubscribeToBestBlocks(e)
-            | BlockError::CouldNotSubscribeToFinalizedBlocks(e) => Some(e),
-            _ => None,
-        }
-    }
-}
-
 #[derive(Debug, thiserror::Error)]
 #[non_exhaustive]
 #[allow(missing_docs)]
@@ -446,56 +474,6 @@ impl AccountNonceError {
     }
 }
 
-#[derive(Debug, thiserror::Error)]
-#[non_exhaustive]
-#[allow(missing_docs)]
-pub enum RuntimeUpdaterError {
-    #[error("Error subscribing to runtime updates: The update stream ended unexpectedly")]
-    UnexpectedEndOfUpdateStream,
-    #[error("Error subscribing to runtime updates: The finalized block stream ended unexpectedly")]
-    UnexpectedEndOfBlockStream,
-    #[error("Error subscribing to runtime updates: Can't stream runtime version: {0}")]
-    CannotStreamRuntimeVersion(BackendError),
-    #[error("Error subscribing to runtime updates: Can't get next runtime version in stream: {0}")]
-    CannotGetNextRuntimeVersion(BackendError),
-    #[error("Error subscribing to runtime updates: Cannot stream finalized blocks: {0}")]
-    CannotStreamFinalizedBlocks(BackendError),
-    #[error("Error subscribing to runtime updates: Cannot get next finalized block in stream: {0}")]
-    CannotGetNextFinalizedBlock(BackendError),
-    #[error("Cannot fetch new metadata for runtime update: {0}")]
-    CannotFetchNewMetadata(BackendError),
-    #[error(
-        "Error subscribing to runtime updates: Cannot find the System.LastRuntimeUpgrade storage entry"
-    )]
-    CantFindSystemLastRuntimeUpgrade,
-    #[error("Error subscribing to runtime updates: Cannot fetch last runtime upgrade: {0}")]
-    CantFetchLastRuntimeUpgrade(StorageError),
-    #[error("Error subscribing to runtime updates: Cannot decode last runtime upgrade: {0}")]
-    CannotDecodeLastRuntimeUpgrade(StorageValueError),
-}
-
-impl RuntimeUpdaterError {
-    fn backend_error(&self) -> Option<&BackendError> {
-        match self {
-            RuntimeUpdaterError::CannotStreamRuntimeVersion(e)
-            | RuntimeUpdaterError::CannotGetNextRuntimeVersion(e)
-            | RuntimeUpdaterError::CannotStreamFinalizedBlocks(e)
-            | RuntimeUpdaterError::CannotGetNextFinalizedBlock(e)
-            | RuntimeUpdaterError::CannotFetchNewMetadata(e) => Some(e),
-            _ => None,
-        }
-    }
-}
-
-/// Error that can occur during upgrade.
-#[non_exhaustive]
-#[derive(Debug, thiserror::Error)]
-#[allow(missing_docs)]
-pub enum RuntimeUpdateeApplyError {
-    #[error("The proposed runtime update is the same as the current version")]
-    SameVersion,
-}
-
 /// Error working with Runtime APIs
 #[non_exhaustive]
 #[derive(Debug, thiserror::Error)]
@@ -704,6 +682,12 @@ pub enum CustomValueError {
     CouldNotDecodeCustomValue(frame_decode::custom_values::CustomValueDecodeError<u32>),
 }
 
+impl CustomValueError {
+    fn backend_error(&self) -> Option<&BackendError> {
+        None
+    }
+}
+
 /// Error working with View Functions.
 #[non_exhaustive]
 #[derive(Debug, thiserror::Error)]
@@ -781,6 +765,12 @@ pub enum TransactionStatusError {
     Dropped(String),
 }
 
+impl TransactionStatusError {
+    fn backend_error(&self) -> Option<&BackendError> {
+        None
+    }
+}
+
 /// Error fetching events for a just-submitted transaction
 #[derive(Debug, thiserror::Error)]
 #[non_exhaustive]
@@ -876,6 +866,12 @@ pub enum ModuleErrorDetailsError {
     },
 }
 
+impl ModuleErrorDetailsError {
+    fn backend_error(&self) -> Option<&BackendError> {
+        None
+    }
+}
+
 /// Error decoding the [`ModuleError`]
 #[derive(Debug, thiserror::Error)]
 #[non_exhaustive]
@@ -883,6 +879,12 @@ pub enum ModuleErrorDetailsError {
 #[error("Could not decode the DispatchError::Module payload into the given type: {0}")]
 pub struct ModuleErrorDecodeError(scale_decode::Error);
 
+impl ModuleErrorDecodeError {
+    fn backend_error(&self) -> Option<&BackendError> {
+        None
+    }
+}
+
 /// Error decoding the [`DispatchError`]
 #[derive(Debug, thiserror::Error)]
 #[non_exhaustive]
@@ -901,6 +903,12 @@ pub enum DispatchErrorDecodeError {
     },
 }
 
+impl DispatchErrorDecodeError {
+    fn backend_error(&self) -> Option<&BackendError> {
+        None
+    }
+}
+
 /// Error working with storage.
 #[derive(Debug, thiserror::Error)]
 #[non_exhaustive]
@@ -984,6 +992,12 @@ pub enum ConstantError {
     ConstantInfoError(frame_decode::constants::ConstantInfoError<'static>),
 }
 
+impl ConstantError {
+    fn backend_error(&self) -> Option<&BackendError> {
+        None
+    }
+}
+
 #[derive(Debug, DeriveError)]
 #[non_exhaustive]
 #[allow(missing_docs)]
@@ -1006,6 +1020,12 @@ pub enum StorageKeyError {
     },
 }
 
+impl StorageKeyError {
+    fn backend_error(&self) -> Option<&BackendError> {
+        None
+    }
+}
+
 #[derive(Debug, DeriveError)]
 #[non_exhaustive]
 #[allow(missing_docs)]
@@ -1018,6 +1038,12 @@ pub enum StorageValueError {
     LeftoverBytes { bytes: Vec<u8> },
 }
 
+impl StorageValueError {
+    fn backend_error(&self) -> Option<&BackendError> {
+        None
+    }
+}
+
 #[derive(Debug, thiserror::Error)]
 #[non_exhaustive]
 #[allow(missing_docs)]
@@ -1027,6 +1053,12 @@ pub struct ExtrinsicDecodeErrorAt {
     pub error: ExtrinsicDecodeErrorAtReason,
 }
 
+impl ExtrinsicDecodeErrorAt {
+    fn backend_error(&self) -> Option<&BackendError> {
+        None
+    }
+}
+
 #[derive(Debug, thiserror::Error)]
 #[non_exhaustive]
 #[allow(missing_docs)]

new/src/error/dispatch_error.rs

@@ -6,10 +6,10 @@
 //! something fails in trying to submit/execute a transaction.
 
 use super::{DispatchErrorDecodeError, ModuleErrorDecodeError, ModuleErrorDetailsError};
-use subxt_metadata::Metadata;
 use core::fmt::Debug;
 use scale_decode::{DecodeAsType, TypeResolver, visitor::DecodeAsTypeResult};
 use std::{borrow::Cow, marker::PhantomData};
+use subxt_metadata::Metadata;
 
 /// An error dispatching a transaction.
 #[derive(Debug, thiserror::Error, PartialEq, Eq)]

new/src/lib.rs

@@ -32,11 +32,11 @@ mod only_used_in_docs_or_tests {
 // #[macro_use]
 // mod macros;
 
-pub mod config;
+pub mod backend;
 pub mod client;
+pub mod config;
 pub mod error;
 pub mod utils;
-pub mod backend;
 // pub mod book;
 // pub mod blocks;
 // pub mod constants;

new/src/utils.rs

@@ -10,22 +10,22 @@ pub mod bits;
 mod era;
 mod multi_address;
 mod multi_signature;
+mod range_map;
 mod static_type;
 mod unchecked_extrinsic;
 mod wrapper_opaque;
 mod yesnomaybe;
-mod range_map;
 
 use codec::{Compact, Decode, Encode};
 use derive_where::derive_where;
 
-pub use range_map::{ RangeMap, RangeMapBuilder, RangeMapError };
 pub use account_id::AccountId32;
 pub use account_id20::AccountId20;
 pub use era::Era;
 pub use multi_address::MultiAddress;
 pub use multi_signature::MultiSignature;
 pub use primitive_types::{H160, H256, H512};
+pub use range_map::{RangeMap, RangeMapBuilder, RangeMapError};
 pub use static_type::Static;
 pub use unchecked_extrinsic::UncheckedExtrinsic;
 pub use wrapper_opaque::WrapperKeepOpaque;

new/src/utils/range_map.rs

@@ -110,7 +110,7 @@ pub enum RangeMapError<K: Display> {
         /// The range being proposed / added.
         proposed: (K, K),
         /// The existing range which overlaps.
-        existing: (K, K) 
+        existing: (K, K),
     },
 }
 

new/src/utils/unchecked_extrinsic.rs

@@ -9,10 +9,10 @@
 //! runtime APIs. Deriving `EncodeAsType` would lead to the inner
 //! bytes to be re-encoded (length prefixed).
 
-use core::marker::PhantomData;
-use codec::{Decode, Encode};
-use scale_decode::{DecodeAsType, IntoVisitor, TypeResolver, Visitor, visitor::DecodeAsTypeResult};
 use super::{Encoded, Static};
+use codec::{Decode, Encode};
+use core::marker::PhantomData;
+use scale_decode::{DecodeAsType, IntoVisitor, TypeResolver, Visitor, visitor::DecodeAsTypeResult};
 
 /// The unchecked extrinsic from substrate.
 #[derive(Clone, Debug, Eq, PartialEq, Encode)]