[WIP] Allow metadata to be filtered to contain only the pallet information asked for

bin/node-template/runtime/src/lib.rs

@@ -359,6 +359,9 @@ impl_runtime_apis! {
 	}
 
 	impl sp_api::Metadata<Block> for Runtime {
+		fn metadata_for_pallets(pallets_to_keep: Vec<Vec<u8>>) -> OpaqueMetadata {
+			OpaqueMetadata::new(Runtime::metadata_for_pallets(pallets_to_keep).into())
+		}
 		fn metadata() -> OpaqueMetadata {
 			OpaqueMetadata::new(Runtime::metadata().into())
 		}

bin/node/runtime/src/lib.rs

@@ -1799,6 +1799,9 @@ impl_runtime_apis! {
 	}
 
 	impl sp_api::Metadata<Block> for Runtime {
+		fn metadata_for_pallets(pallets_to_keep: Vec<Vec<u8>>) -> OpaqueMetadata {
+			OpaqueMetadata::new(Runtime::metadata_for_pallets(pallets_to_keep).into())
+		}
 		fn metadata() -> OpaqueMetadata {
 			OpaqueMetadata::new(Runtime::metadata().into())
 		}

client/rpc-api/src/state/mod.rs

@@ -76,7 +76,7 @@ pub trait StateApi<Hash> {
 
 	/// Returns the runtime metadata as an opaque blob.
 	#[method(name = "state_getMetadata", blocking)]
-	fn metadata(&self, hash: Option<Hash>) -> RpcResult<Bytes>;
+	fn metadata(&self, pallets: Option<Vec<String>>, hash: Option<Hash>) -> RpcResult<Bytes>;
 
 	/// Get the runtime version.
 	#[method(name = "state_getRuntimeVersion", aliases = ["chain_getRuntimeVersion"], blocking)]

client/rpc/src/state/mod.rs

@@ -115,7 +115,9 @@ where
 	) -> Result<Option<u64>, Error>;
 
 	/// Returns the runtime metadata as an opaque blob.
-	fn metadata(&self, block: Option<Block::Hash>) -> Result<Bytes, Error>;
+	///
+	/// If a list of pallet names is provided, only metadata for those pallets will be returned.
+	fn metadata(&self, pallets: Option<Vec<String>>, block: Option<Block::Hash>) -> Result<Bytes, Error>;
 
 	/// Get the runtime version.
 	fn runtime_version(&self, block: Option<Block::Hash>) -> Result<RuntimeVersion, Error>;
@@ -267,8 +269,8 @@ where
 		self.backend.storage_size(block, key).map_err(Into::into)
 	}
 
-	fn metadata(&self, block: Option<Block::Hash>) -> RpcResult<Bytes> {
-		self.backend.metadata(block).map_err(Into::into)
+	fn metadata(&self, pallets: Option<Vec<String>>, block: Option<Block::Hash>) -> RpcResult<Bytes> {
+		self.backend.metadata(pallets, block).map_err(Into::into)
 	}
 
 	fn runtime_version(&self, at: Option<Block::Hash>) -> RpcResult<RuntimeVersion> {

client/rpc/src/state/state_full.rs

@@ -296,11 +296,19 @@ where
 			.map_err(client_err)
 	}
 
-	fn metadata(&self, block: Option<Block::Hash>) -> std::result::Result<Bytes, Error> {
+	fn metadata(&self, pallets: Option<Vec<String>>, block: Option<Block::Hash>) -> std::result::Result<Bytes, Error> {
 		self.block_or_best(block).map_err(client_err).and_then(|block| {
-			self.client
-				.runtime_api()
-				.metadata(&BlockId::Hash(block))
+			let api = self.client.runtime_api();
+
+			let metadata = match pallets {
+				Some(pallet_names) => {
+					let name_bytes = pallet_names.into_iter().map(|n| n.into_bytes()).collect();
+					api.metadata_for_pallets(&BlockId::Hash(block), name_bytes)
+				},
+				None => api.metadata(&BlockId::Hash(block))
+			};
+
+			metadata
 				.map(Into::into)
 				.map_err(|e| Error::Client(Box::new(e)))
 		})

frame/support/procedural/src/construct_runtime/expand/metadata.rs

@@ -74,9 +74,25 @@ pub fn expand_runtime_metadata(
 
 	quote! {
 		impl #runtime {
+			pub fn metadata_for_pallets(pallets_to_keep: #scrate::sp_std::vec::Vec<#scrate::sp_std::vec::Vec<u8>>) -> #scrate::metadata::RuntimeMetadataPrefixed {
+				Self::metadata_inner(Some(pallets_to_keep))
+			}
 			pub fn metadata() -> #scrate::metadata::RuntimeMetadataPrefixed {
+				Self::metadata_inner(None)
+			}
+			fn metadata_inner(pallets_to_keep: Option<#scrate::sp_std::vec::Vec<#scrate::sp_std::vec::Vec<u8>>>) -> #scrate::metadata::RuntimeMetadataPrefixed {
+				let mut pallets = #scrate::sp_std::vec![ #(#pallets),* ];
+
+				// Filter pallet list to only include those asked for, if provided.
+				if let Some(pallet_names_to_keep) = pallets_to_keep {
+					pallets = pallets
+						.into_iter()
+						.filter(|p| pallet_names_to_keep.iter().any(|n| n == p.name.as_bytes()))
+						.collect();
+				}
+
 				#scrate::metadata::RuntimeMetadataLastVersion::new(
-					#scrate::sp_std::vec![ #(#pallets),* ],
+					pallets,
 					#scrate::metadata::ExtrinsicMetadata {
 						ty: #scrate::scale_info::meta_type::<#extrinsic>(),
 						version: <#extrinsic as #scrate::sp_runtime::traits::ExtrinsicMetadata>::VERSION,

primitives/api/src/lib.rs

@@ -730,6 +730,9 @@ decl_runtime_apis! {
 
 	/// The `Metadata` api trait that returns metadata for the runtime.
 	pub trait Metadata {
+		/// Returns the metadata of a runtime filtered to contain only
+		/// details about the list of pallets provided.
+		fn metadata_for_pallets(pallets_to_keep: sp_std::vec::Vec<sp_std::vec::Vec<u8>>) -> OpaqueMetadata;
 		/// Returns the metadata of a runtime.
 		fn metadata() -> OpaqueMetadata;
 	}

test-utils/runtime/src/lib.rs

@@ -710,6 +710,9 @@ cfg_if! {
 			}
 
 			impl sp_api::Metadata<Block> for Runtime {
+				fn metadata_for_pallets(_pallet_names: Vec<Vec<u8>>) -> OpaqueMetadata {
+					unimplemented!()
+				}
 				fn metadata() -> OpaqueMetadata {
 					unimplemented!()
 				}
@@ -980,6 +983,9 @@ cfg_if! {
 			}
 
 			impl sp_api::Metadata<Block> for Runtime {
+				fn metadata_for_pallets(pallet_names_to_keep: Vec<Vec<u8>>) -> OpaqueMetadata {
+					unimplemented!()
+				}
 				fn metadata() -> OpaqueMetadata {
 					unimplemented!()
 				}