Adds export-state subcommand (#5842)

* Export state cli

* More work

* Fix tests

* Make it work

* Fix compilation

* Apply suggestions from code review

substrate/client/service/src/chain_ops.rs

@@ -33,13 +33,14 @@ use sp_consensus::{
 	import_queue::{IncomingBlock, Link, BlockImportError, BlockImportResult, ImportQueue},
 };
 use sc_executor::{NativeExecutor, NativeExecutionDispatch};
+use sp_core::storage::{StorageKey, well_known_keys, ChildInfo, Storage, StorageChild, StorageMap};
+use sc_client_api::{StorageProvider, BlockBackend, UsageProvider};
 
-use std::{io::{Read, Write, Seek}, pin::Pin};
-use sc_client_api::BlockBackend;
+use std::{io::{Read, Write, Seek}, pin::Pin, collections::HashMap};
 
 /// Build a chain spec json
 pub fn build_spec(spec: &dyn ChainSpec, raw: bool) -> error::Result<String> {
-	Ok(spec.as_json(raw)?)
+	spec.as_json(raw).map_err(Into::into)
 }
 
 impl<
@@ -298,4 +299,45 @@ impl<
 			Err(e) => Box::pin(future::err(format!("Error reading block: {:?}", e).into())),
 		}
 	}
+
+	fn export_raw_state(
+		&self,
+		block: Option<BlockId<Self::Block>>,
+	) -> Result<Storage, Error> {
+		let block = block.unwrap_or_else(
+			|| BlockId::Hash(self.client.usage_info().chain.best_hash)
+		);
+
+		let empty_key = StorageKey(Vec::new());
+		let mut top_storage = self.client.storage_pairs(&block, &empty_key)?;
+		let mut children_default = HashMap::new();
+
+		// Remove all default child storage roots from the top storage and collect the child storage
+		// pairs.
+		while let Some(pos) = top_storage
+			.iter()
+			.position(|(k, _)| k.0.starts_with(well_known_keys::DEFAULT_CHILD_STORAGE_KEY_PREFIX)) {
+			let (key, _) = top_storage.swap_remove(pos);
+
+			let key = StorageKey(
+				key.0[well_known_keys::DEFAULT_CHILD_STORAGE_KEY_PREFIX.len()..].to_vec(),
+			);
+			let child_info = ChildInfo::new_default(&key.0);
+
+			let keys = self.client.child_storage_keys(&block, &child_info, &empty_key)?;
+			let mut pairs = StorageMap::new();
+			keys.into_iter().try_for_each(|k| {
+				if let Some(value) = self.client.child_storage(&block, &child_info, &k)? {
+					pairs.insert(k.0, value.0);
+				}
+
+				Ok::<_, Error>(())
+			})?;
+
+			children_default.insert(key.0, StorageChild { child_info, data: pairs });
+		}
+
+		let top = top_storage.into_iter().map(|(k, v)| (k.0, v.0)).collect();
+		Ok(Storage { top, children_default })
+	}
 }