Adds json_metadata RPC call

substrate/client/src/client.rs

@@ -251,6 +251,13 @@ impl<B, E, Block> Client<B, E, Block> where
 		&self.executor
 	}
 
+	/// Returns the runtime metadata as JSON.
+	pub fn json_metadata(&self, id: &BlockId<Block>) -> error::Result<String> {
+		self.executor.call(id, "json_metadata",&[])
+			.and_then(|r| String::decode(&mut &r.return_data[..])
+					  .ok_or("Metadata decoding failed".into()))
+	}
+
 	/// Reads storage value at a given block + key, returning read proof.
 	pub fn read_proof(&self, id: &BlockId<Block>, key: &[u8]) -> error::Result<Vec<Vec<u8>>> {
 		self.state_at(id)

substrate/rpc/Cargo.toml

@@ -19,6 +19,7 @@ substrate-runtime-primitives = { path = "../runtime/primitives" }
 substrate-runtime-version = { path = "../runtime/version" }
 substrate-state-machine = { path = "../state-machine" }
 tokio = "0.1.7"
+serde_json = "1.0"
 
 [dev-dependencies]
 assert_matches = "1.1"

substrate/rpc/src/lib.rs

@@ -29,6 +29,7 @@ extern crate substrate_runtime_primitives as runtime_primitives;
 extern crate substrate_state_machine as state_machine;
 extern crate substrate_runtime_version as runtime_version;
 extern crate tokio;
+extern crate serde_json;
 
 #[macro_use]
 extern crate error_chain;

substrate/rpc/src/state/error.rs

@@ -19,11 +19,17 @@ use rpc;
 
 use errors;
 
+use serde_json;
+
 error_chain! {
 	links {
 		Client(client::error::Error, client::error::ErrorKind) #[doc = "Client error"];
 	}
 
+	foreign_links {
+		Json(serde_json::Error);
+	}
+
 	errors {
 		/// Provided block range couldn't be resolved to a list of blocks.
 		InvalidBlockRange(from: String, to: String, details: String) {

substrate/rpc/src/state/mod.rs

@@ -33,6 +33,7 @@ use rpc::futures::{stream, Future, Sink, Stream};
 use runtime_primitives::generic::BlockId;
 use runtime_primitives::traits::{Block as BlockT, Header};
 use tokio::runtime::TaskExecutor;
+use serde_json;
 
 use subscriptions::Subscriptions;
 
@@ -63,6 +64,10 @@ build_rpc_trait! {
 		#[rpc(name = "state_getStorageSize", alias = ["state_getStorageSizeAt", ])]
 		fn storage_size(&self, StorageKey, Trailing<Hash>) -> Result<Option<u64>>;
 
+		/// Returns the runtime metadata as JSON.
+		#[rpc(name = "state_metadata", alias = ["state_metadataAt", ])]
+		fn json_metadata(&self, Trailing<Hash>) -> Result<serde_json::Value>;
+
 		/// Query historical storage entries (by key) starting from a block given as the second parameter.
 		///
 		/// NOTE This first returned result contains the initial state of storage for all keys.
@@ -138,6 +143,12 @@ impl<B, E, Block> StateApi<Block::Hash> for State<B, E, Block> where
 		Ok(self.storage(key, block)?.map(|x| x.0.len() as u64))
 	}
 
+	fn json_metadata(&self, block: Trailing<Block::Hash>) -> Result<serde_json::Value> {
+		let block = self.unwrap_or_best(block)?;
+		let metadata = self.client.json_metadata(&BlockId::Hash(block))?;
+		serde_json::from_str(&metadata).map_err(Into::into)
+	}
+
 	fn query_storage(&self, keys: Vec<StorageKey>, from: Block::Hash, to: Trailing<Block::Hash>) -> Result<Vec<StorageChangeSet<Block::Hash>>> {
 		let to = self.unwrap_or_best(to)?;