fix(testnet): metadata api (#511)

* fix(testnet): metadata api

* test(mainnet): metadata api

* fix: copilot docs improvements

Author: Daanvdplas

Cargo.lock

@@ -81,6 +81,7 @@ pop-runtime-testnet = { path = "runtime/testnet", default-features = true } # de
 frame-benchmarking = { git = "https://github.com/paritytech/polkadot-sdk", branch = "stable2412", default-features = false }
 frame-benchmarking-cli = { git = "https://github.com/paritytech/polkadot-sdk", branch = "stable2412" }
 frame-executive = { git = "https://github.com/paritytech/polkadot-sdk", branch = "stable2412", default-features = false }
+frame-metadata = { version = "18.0.0", default-features = false }
 frame-metadata-hash-extension = { git = "https://github.com/paritytech/polkadot-sdk", branch = "stable2412", default-features = false }
 frame-support = { git = "https://github.com/paritytech/polkadot-sdk", branch = "stable2412", default-features = false }
 frame-system = { git = "https://github.com/paritytech/polkadot-sdk", branch = "stable2412", default-features = false }

Cargo.toml

@@ -94,6 +94,7 @@ parachains-common.workspace = true
 [dev-dependencies]
 enumflags2 = "0.7.9"
 env_logger = "0.11.2"
+frame-metadata.workspace = true
 hex = "0.4.3"
 polkadot-runtime-parachains.workspace = true
 sp-keyring.workspace = true

runtime/mainnet/Cargo.toml

@@ -505,3 +505,42 @@ impl_runtime_apis! {
 		}
 	}
 }
+
+#[test]
+fn metadata_api_implemented() {
+	use core::ops::Deref;
+
+	use codec::Decode;
+	use frame_metadata::{RuntimeMetadata, RuntimeMetadataPrefixed};
+	const V16_UNSTABLE: u32 = u32::MAX;
+
+	fn assert<T: sp_api::runtime_decl_for_metadata::Metadata<Block>>() {
+		let opaque_meta: OpaqueMetadata = T::metadata();
+		let prefixed_meta = RuntimeMetadataPrefixed::decode(&mut &opaque_meta.deref()[..]).unwrap();
+		assert_eq!(prefixed_meta, Runtime::metadata());
+		// Always returns metadata v14:
+		// https://github.com/paritytech/polkadot-sdk/blob/c36d3066c082b769f20c31dfdbae77d8fd027a0d/substrate/frame/support/procedural/src/construct_runtime/expand/metadata.rs#L151
+		let RuntimeMetadata::V14(_) = prefixed_meta.1 else {
+			panic!("Expected metadata V14");
+		};
+
+		assert_eq!(T::metadata_versions(), vec![14, 15, V16_UNSTABLE]);
+
+		let version = 15;
+		let opaque_meta = T::metadata_at_version(version).expect("V15 should exist");
+		let prefixed_meta_bytes = opaque_meta.deref();
+		assert_eq!(prefixed_meta_bytes, Runtime::metadata_at_version(version).unwrap().deref());
+		let prefixed_meta = RuntimeMetadataPrefixed::decode(&mut &prefixed_meta_bytes[..]).unwrap();
+		// Ensure that we have the V15 variant.
+		let RuntimeMetadata::V15(metadata) = prefixed_meta.1 else {
+			panic!("Expected metadata V15");
+		};
+		// TODO: This shouldn't be empty and should be resolved with 2503.
+		assert!(metadata.apis.is_empty());
+		assert!(!metadata.pallets.is_empty());
+
+		// Ensure metadata v16 is not provided.
+		assert!(T::metadata_at_version(16).is_none());
+	}
+	sp_io::TestExternalities::new_empty().execute_with(|| assert::<Runtime>());
+}

runtime/mainnet/src/apis.rs

@@ -107,6 +107,7 @@ pallet-ismp-runtime-api.workspace = true
 [dev-dependencies]
 enumflags2.workspace = true
 env_logger.workspace = true
+frame-metadata.workspace = true
 hex.workspace = true
 
 [features]