Add Runtime API to execute runtime calls (#777)

* rpc: Add RuntimeAPI call via `state_call` method

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* subxt: Add runtime API

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Expose the RuntimeAPI client

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* tests: Test the runtime API call against the metadata

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* client: Fetch the metadata from runtime API

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* blocks: Fix doc typo

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* blocks: Use &str instead of String to identify fn names

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* Update subxt/src/runtime_api/runtime_client.rs

Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com>

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>
Co-authored-by: Niklas Adolfsson <niklasadolfsson1@gmail.com>

subxt/src/blocks/block_types.rs

@@ -18,6 +18,7 @@ use crate::{
     },
     events,
     rpc::types::ChainBlockResponse,
+    runtime_api::RuntimeApi,
 };
 use derivative::Derivative;
 use futures::lock::Mutex as AsyncMutex;
@@ -89,6 +90,11 @@ where
             self.cached_events.clone(),
         ))
     }
+
+    /// Execute a runtime API call at this block.
+    pub async fn runtime_api(&self) -> Result<RuntimeApi<T, C>, Error> {
+        Ok(RuntimeApi::new(self.client.clone(), self.hash()))
+    }
 }
 
 /// The body of a block.

subxt/src/client/offline_client.rs

@@ -7,6 +7,7 @@ use crate::{
     constants::ConstantsClient,
     events::EventsClient,
     rpc::types::RuntimeVersion,
+    runtime_api::RuntimeApiClient,
     storage::StorageClient,
     tx::TxClient,
     Config,
@@ -49,6 +50,11 @@ pub trait OfflineClientT<T: Config>: Clone + Send + Sync + 'static {
     fn blocks(&self) -> BlocksClient<T, Self> {
         BlocksClient::new(self.clone())
     }
+
+    /// Work with runtime API.
+    fn runtime_api(&self) -> RuntimeApiClient<T, Self> {
+        RuntimeApiClient::new(self.clone())
+    }
 }
 
 /// A client that is capable of performing offline-only operations.

subxt/src/client/online_client.rs

@@ -19,12 +19,18 @@ use crate::{
         Rpc,
         RpcClientT,
     },
+    runtime_api::RuntimeApiClient,
     storage::StorageClient,
     tx::TxClient,
     Config,
     Metadata,
 };
+use codec::{
+    Compact,
+    Decode,
+};
 use derivative::Derivative;
+use frame_metadata::RuntimeMetadataPrefixed;
 use futures::future;
 use parking_lot::RwLock;
 use std::sync::Arc;
@@ -95,7 +101,7 @@ impl<T: Config> OnlineClient<T> {
         let (genesis_hash, runtime_version, metadata) = future::join3(
             rpc.genesis_hash(),
             rpc.runtime_version(None),
-            rpc.metadata(None),
+            OnlineClient::fetch_metadata(&rpc),
         )
         .await;
 
@@ -109,6 +115,15 @@ impl<T: Config> OnlineClient<T> {
         })
     }
 
+    /// Fetch the metadata from substrate using the runtime API.
+    async fn fetch_metadata(rpc: &Rpc<T>) -> Result<Metadata, Error> {
+        let bytes = rpc.state_call("Metadata_metadata", None, None).await?;
+        let cursor = &mut &*bytes;
+        let _ = <Compact<u32>>::decode(cursor)?;
+        let meta: RuntimeMetadataPrefixed = Decode::decode(cursor)?;
+        Ok(meta.try_into()?)
+    }
+
     /// Create an object which can be used to keep the runtime up to date
     /// in a separate thread.
     ///
@@ -214,6 +229,11 @@ impl<T: Config> OnlineClient<T> {
     pub fn blocks(&self) -> BlocksClient<T, Self> {
         <Self as OfflineClientT<T>>::blocks(self)
     }
+
+    /// Work with runtime API.
+    pub fn runtime_api(&self) -> RuntimeApiClient<T, Self> {
+        <Self as OfflineClientT<T>>::runtime_api(self)
+    }
 }
 
 impl<T: Config> OfflineClientT<T> for OnlineClient<T> {

subxt/src/lib.rs

@@ -155,6 +155,7 @@ pub mod error;
 pub mod events;
 pub mod metadata;
 pub mod rpc;
+pub mod runtime_api;
 pub mod storage;
 pub mod tx;
 pub mod utils;

subxt/src/rpc/rpc.rs

@@ -371,6 +371,25 @@ impl<T: Config> Rpc<T> {
         Ok(xt_hash)
     }
 
+    /// Execute a runtime API call.
+    pub async fn state_call(
+        &self,
+        function: &str,
+        call_parameters: Option<&[u8]>,
+        at: Option<T::Hash>,
+    ) -> Result<types::Bytes, Error> {
+        let call_parameters = call_parameters.unwrap_or_default();
+
+        let bytes: types::Bytes = self
+            .client
+            .request(
+                "state_call",
+                rpc_params![function, to_hex(call_parameters), at],
+            )
+            .await?;
+        Ok(bytes)
+    }
+
     /// Create and submit an extrinsic and return a subscription to the events triggered.
     pub async fn watch_extrinsic<X: Encode>(
         &self,

subxt/src/runtime_api/mod.rs

@@ -0,0 +1,11 @@
+// Copyright 2019-2022 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+//! Types associated with executing runtime API calls.
+
+mod runtime_client;
+mod runtime_types;
+
+pub use runtime_client::RuntimeApiClient;
+pub use runtime_types::RuntimeApi;

subxt/src/runtime_api/runtime_client.rs

@@ -0,0 +1,66 @@
+// Copyright 2019-2022 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+use super::runtime_types::RuntimeApi;
+
+use crate::{
+    client::OnlineClientT,
+    error::Error,
+    Config,
+};
+use derivative::Derivative;
+use std::{
+    future::Future,
+    marker::PhantomData,
+};
+
+/// Execute runtime API calls.
+#[derive(Derivative)]
+#[derivative(Clone(bound = "Client: Clone"))]
+pub struct RuntimeApiClient<T, Client> {
+    client: Client,
+    _marker: PhantomData<T>,
+}
+
+impl<T, Client> RuntimeApiClient<T, Client> {
+    /// Create a new [`RuntimeApiClient`]
+    pub fn new(client: Client) -> Self {
+        Self {
+            client,
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<T, Client> RuntimeApiClient<T, Client>
+where
+    T: Config,
+    Client: OnlineClientT<T>,
+{
+    /// Obtain a runtime API at some block hash.
+    pub fn at(
+        &self,
+        block_hash: Option<T::Hash>,
+    ) -> impl Future<Output = Result<RuntimeApi<T, Client>, Error>> + Send + 'static {
+        // Clone and pass the client in like this so that we can explicitly
+        // return a Future that's Send + 'static, rather than tied to &self.
+        let client = self.client.clone();
+        async move {
+            // If block hash is not provided, get the hash
+            // for the latest block and use that.
+            let block_hash = match block_hash {
+                Some(hash) => hash,
+                None => {
+                    client
+                        .rpc()
+                        .block_hash(None)
+                        .await?
+                        .expect("substrate RPC returns the best block when no block number is provided; qed")
+                }
+            };
+
+            Ok(RuntimeApi::new(client, block_hash))
+        }
+    }
+}

subxt/src/runtime_api/runtime_types.rs

@@ -0,0 +1,59 @@
+// Copyright 2019-2022 Parity Technologies (UK) Ltd.
+// This file is dual-licensed as Apache-2.0 or GPL-3.0.
+// see LICENSE for license details.
+
+use crate::{
+    client::OnlineClientT,
+    error::Error,
+    Config,
+};
+use derivative::Derivative;
+use std::{
+    future::Future,
+    marker::PhantomData,
+};
+
+/// Execute runtime API calls.
+#[derive(Derivative)]
+#[derivative(Clone(bound = "Client: Clone"))]
+pub struct RuntimeApi<T: Config, Client> {
+    client: Client,
+    block_hash: T::Hash,
+    _marker: PhantomData<T>,
+}
+
+impl<T: Config, Client> RuntimeApi<T, Client> {
+    /// Create a new [`RuntimeApi`]
+    pub(crate) fn new(client: Client, block_hash: T::Hash) -> Self {
+        Self {
+            client,
+            block_hash,
+            _marker: PhantomData,
+        }
+    }
+}
+
+impl<T, Client> RuntimeApi<T, Client>
+where
+    T: Config,
+    Client: OnlineClientT<T>,
+{
+    /// Execute a raw runtime API call.
+    pub fn call_raw<'a>(
+        &self,
+        function: &'a str,
+        call_parameters: Option<&'a [u8]>,
+    ) -> impl Future<Output = Result<Vec<u8>, Error>> + 'a {
+        let client = self.client.clone();
+        let block_hash = self.block_hash;
+        // Ensure that the returned future doesn't have a lifetime tied to api.runtime_api(),
+        // which is a temporary thing we'll be throwing away quickly:
+        async move {
+            let data = client
+                .rpc()
+                .state_call(function, call_parameters, Some(block_hash))
+                .await?;
+            Ok(data.0)
+        }
+    }
+}