fix: runtime API implementations not exported (#809)

Fixes KILTprotocol/ticket#3688.

Due to how the `impl_runtime_apis` macro works, it is expected to be
included in a runtime's `lib.rs` file. Since we split up the runtimes,
the runtime APIs were not included anymore. I found a related issue in
the subxt repo: paritytech/subxt#1873.

Because the trait definition generated by the macro is local, we can't
import it in the `lib.rs` module for the `construct_runtime` macro to
pick up the right implementation, so we need a workaround that basically
introduces a new marker trait, and we import _that_ in the `lib.rs` file
so that the right implementation of `Runtime::runtime_metadata()` is
picked up. More details about the issue are presented in the subxt
ticket.

## How to test

Spin up a chopsticks deployment after building peregrine and spiritnet
runtime, and verify that the runtime APIs are there now.

Author: ntn-x2

Cargo.lock

@@ -169,6 +169,7 @@ sp-core                                    = { git = "https://github.com/parityt
 sp-genesis-builder                         = { git = "https://github.com/paritytech/polkadot-sdk", default-features = false, branch = "release-crates-io-v1.7.0" }
 sp-inherents                               = { git = "https://github.com/paritytech/polkadot-sdk", default-features = false, branch = "release-crates-io-v1.7.0" }
 sp-io                                      = { git = "https://github.com/paritytech/polkadot-sdk", default-features = false, branch = "release-crates-io-v1.7.0" }
+sp-metadata-ir                             = { git = "https://github.com/paritytech/polkadot-sdk", default-features = false, branch = "release-crates-io-v1.7.0" }
 sp-offchain                                = { git = "https://github.com/paritytech/polkadot-sdk", default-features = false, branch = "release-crates-io-v1.7.0" }
 sp-runtime                                 = { git = "https://github.com/paritytech/polkadot-sdk", default-features = false, branch = "release-crates-io-v1.7.0" }
 sp-session                                 = { git = "https://github.com/paritytech/polkadot-sdk", default-features = false, branch = "release-crates-io-v1.7.0" }

Cargo.toml

@@ -59,6 +59,7 @@ sp-block-builder    = { workspace = true }
 sp-consensus-aura   = { workspace = true }
 sp-core             = { workspace = true }
 sp-inherents        = { workspace = true }
+sp-metadata-ir      = { workspace = true }
 sp-offchain         = { workspace = true }
 sp-runtime          = { workspace = true }
 sp-session          = { workspace = true }
@@ -241,6 +242,7 @@ std = [
   "sp-core/std",
   "sp-genesis-builder/std",
   "sp-inherents/std",
+  "sp-metadata-ir/std",
   "sp-offchain/std",
   "sp-runtime/std",
   "sp-session/std",

runtimes/peregrine/Cargo.toml

@@ -54,6 +54,7 @@ mod migrations;
 pub use migrations::RuntimeMigrations;
 mod parachain;
 mod runtime_apis;
+use runtime_apis::_InternalImplRuntimeApis;
 pub use runtime_apis::{api, RuntimeApi};
 mod system;
 use sp_version::RuntimeVersion;

runtimes/peregrine/src/lib.rs

@@ -16,6 +16,7 @@ use pallet_transaction_payment::{FeeDetails, RuntimeDispatchInfo};
 use sp_api::impl_runtime_apis;
 use sp_core::OpaqueMetadata;
 use sp_inherents::{CheckInherentsResult, InherentData};
+use sp_metadata_ir::RuntimeApiMetadataIR;
 use sp_runtime::{
 	traits::{Block as BlockT, TryConvert},
 	ApplyExtrinsicResult, KeyTypeId,
@@ -53,6 +54,22 @@ use crate::{
 // `impl_runtime_apis` is private.
 pub(crate) const RUNTIME_API_VERSION: ApisVec = RUNTIME_API_VERSIONS;
 
+// Workaround for runtime API impls not exposed in metadata if implemented in a
+// different file than the runtime's `lib.rs`. Related issue (subxt) -> https://github.com/paritytech/subxt/issues/1873.
+pub(crate) trait _InternalImplRuntimeApis {
+	fn runtime_metadata(&self) -> Vec<RuntimeApiMetadataIR>;
+}
+
+impl<T> _InternalImplRuntimeApis for T
+where
+	T: InternalImplRuntimeApis,
+{
+	#[inline(always)]
+	fn runtime_metadata(&self) -> Vec<RuntimeApiMetadataIR> {
+		<T as InternalImplRuntimeApis>::runtime_metadata(self)
+	}
+}
+
 impl_runtime_apis! {
 	impl sp_api::Core<Block> for Runtime {
 		fn version() -> RuntimeVersion {

runtimes/peregrine/src/runtime_apis.rs

@@ -59,6 +59,7 @@ sp-block-builder    = { workspace = true }
 sp-consensus-aura   = { workspace = true }
 sp-core             = { workspace = true }
 sp-inherents        = { workspace = true }
+sp-metadata-ir      = { workspace = true }
 sp-offchain         = { workspace = true }
 sp-runtime          = { workspace = true }
 sp-session          = { workspace = true }
@@ -240,6 +241,7 @@ std = [
   "sp-core/std",
   "sp-genesis-builder/std",
   "sp-inherents/std",
+  "sp-metadata-ir/std",
   "sp-offchain/std",
   "sp-runtime/std",
   "sp-session/std",

runtimes/spiritnet/Cargo.toml

@@ -54,6 +54,7 @@ mod migrations;
 pub use migrations::RuntimeMigrations;
 mod parachain;
 mod runtime_apis;
+use runtime_apis::_InternalImplRuntimeApis;
 pub use runtime_apis::{api, RuntimeApi};
 mod system;
 use sp_version::RuntimeVersion;

runtimes/spiritnet/src/lib.rs

@@ -16,6 +16,7 @@ use pallet_transaction_payment::{FeeDetails, RuntimeDispatchInfo};
 use sp_api::impl_runtime_apis;
 use sp_core::OpaqueMetadata;
 use sp_inherents::{CheckInherentsResult, InherentData};
+use sp_metadata_ir::RuntimeApiMetadataIR;
 use sp_runtime::{
 	traits::{Block as BlockT, TryConvert},
 	ApplyExtrinsicResult, KeyTypeId,
@@ -53,6 +54,22 @@ use crate::{
 // `impl_runtime_apis` is private.
 pub(crate) const RUNTIME_API_VERSION: ApisVec = RUNTIME_API_VERSIONS;
 
+// Workaround for runtime API impls not exposed in metadata if implemented in a
+// different file than the runtime's `lib.rs`. Related issue (subxt) -> https://github.com/paritytech/subxt/issues/1873.
+pub(crate) trait _InternalImplRuntimeApis {
+	fn runtime_metadata(&self) -> Vec<RuntimeApiMetadataIR>;
+}
+
+impl<T> _InternalImplRuntimeApis for T
+where
+	T: InternalImplRuntimeApis,
+{
+	#[inline(always)]
+	fn runtime_metadata(&self) -> Vec<RuntimeApiMetadataIR> {
+		<T as InternalImplRuntimeApis>::runtime_metadata(self)
+	}
+}
+
 impl_runtime_apis! {
 	impl sp_api::Core<Block> for Runtime {
 		fn version() -> RuntimeVersion {