Return account's asset balances

Cargo.toml

@@ -74,6 +74,7 @@ members = [
 	"client/utils",
 	"frame/alliance",
 	"frame/assets",
+	"frame/assets/runtime-api",
 	"frame/atomic-swap",
 	"frame/aura",
 	"frame/authority-discovery",

bin/node/runtime/Cargo.toml

@@ -53,6 +53,7 @@ frame-system-rpc-runtime-api = { version = "4.0.0-dev", default-features = false
 frame-try-runtime = { version = "0.10.0-dev", default-features = false, path = "../../../frame/try-runtime", optional = true }
 pallet-alliance = { version = "4.0.0-dev", default-features = false, path = "../../../frame/alliance" }
 pallet-assets = { version = "4.0.0-dev", default-features = false, path = "../../../frame/assets" }
+pallet-assets-runtime-api = { version = "4.0.0-dev", default-features = false, path = "../../../frame/assets/runtime-api" }
 pallet-authority-discovery = { version = "4.0.0-dev", default-features = false, path = "../../../frame/authority-discovery" }
 pallet-authorship = { version = "4.0.0-dev", default-features = false, path = "../../../frame/authorship" }
 pallet-babe = { version = "4.0.0-dev", default-features = false, path = "../../../frame/babe" }
@@ -128,6 +129,7 @@ std = [
 	"frame-election-provider-support/std",
 	"sp-authority-discovery/std",
 	"pallet-assets/std",
+	"pallet-assets-runtime-api/std",
 	"pallet-authority-discovery/std",
 	"pallet-authorship/std",
 	"sp-consensus-babe/std",

bin/node/runtime/src/lib.rs

@@ -2045,6 +2045,20 @@ impl_runtime_apis! {
 		}
 	}
 
+	impl pallet_assets_runtime_api::AssetsApi<
+		Block,
+		AccountId,
+		Balance,
+		u32,
+	> for Runtime
+	{
+		fn account_balances(instance: u8, account: AccountId) -> Vec<(u32, Balance)> {
+			match instance {
+				_ => Assets::account_balances(instance, account),
+			}
+		}
+	}
+
 	impl pallet_contracts::ContractsApi<Block, AccountId, Balance, BlockNumber, Hash> for Runtime
 	{
 		fn call(

frame/assets/runtime-api/Cargo.toml

@@ -0,0 +1,26 @@
+[package]
+name = "pallet-assets-runtime-api"
+version = "4.0.0-dev"
+authors = ["Parity Technologies <admin@parity.io>"]
+edition = "2021"
+license = "Apache-2.0"
+homepage = "https://substrate.io"
+repository = "https://github.com/paritytech/substrate/"
+description = "Runtime API for assets FRAME pallet"
+readme = "README.md"
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[dependencies]
+codec = { package = "parity-scale-codec", version = "3.2.2", default-features = false, features = ["derive"] }
+sp-api = { version = "4.0.0-dev", default-features = false, path = "../../../primitives/api" }
+sp-std = { version = "5.0.0", default-features = false, path = "../../../primitives/std" }
+
+[features]
+default = ["std"]
+std = [
+	"codec/std",
+	"sp-api/std",
+	"sp-std/std",
+]

frame/assets/runtime-api/README.md

@@ -0,0 +1,3 @@
+Runtime API definition for assets pallet.
+
+License: Apache-2.0

frame/assets/runtime-api/src/lib.rs

@@ -0,0 +1,35 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2022 Parity Technologies (UK) Ltd.
+// SPDX-License-Identifier: Apache-2.0
+
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// 	http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Runtime API definition for assets pallet.
+//! Currently supports only one rpc endpoint.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+use codec::Codec;
+use sp_std::vec::Vec;
+
+sp_api::decl_runtime_apis! {
+	pub trait AssetsApi<AccountId, AssetBalance, AssetId> where
+		AccountId: Codec,
+		AssetBalance: Codec,
+		AssetId: Codec
+	{
+		/// Returns the list of asset id and non-zero balance the AccountId has.
+		fn account_balances(instance: u8, account: AccountId) -> Vec<(AssetId, AssetBalance)>;
+	}
+}

frame/assets/src/functions.rs

@@ -924,4 +924,11 @@ impl<T: Config<I>, I: 'static> Pallet<T, I> {
 			Ok(())
 		})
 	}
+
+	/// Used by the RPC service to provide account balances.
+	pub fn account_balances(_instance: u8, account: T::AccountId) -> Vec<(T::AssetId, T::Balance)> {
+		Asset::<T, I>::iter_keys()
+			.filter_map(|id| Self::maybe_balance(id, account.clone()).map(|balance| (id, balance)))
+			.collect::<Vec<_>>()
+	}
 }

frame/assets/src/tests.rs

@@ -37,11 +37,14 @@ fn asset_ids() -> Vec<u32> {
 fn basic_minting_should_work() {
 	new_test_ext().execute_with(|| {
 		assert_ok!(Assets::force_create(RuntimeOrigin::root(), 0, 1, true, 1));
+		assert_ok!(Assets::force_create(RuntimeOrigin::root(), 1, 1, true, 1));
 		assert_ok!(Assets::mint(RuntimeOrigin::signed(1), 0, 1, 100));
 		assert_eq!(Assets::balance(0, 1), 100);
 		assert_ok!(Assets::mint(RuntimeOrigin::signed(1), 0, 2, 100));
 		assert_eq!(Assets::balance(0, 2), 100);
-		assert_eq!(asset_ids(), vec![0, 999]);
+		assert_eq!(asset_ids(), vec![0, 1, 999]);
+		assert_ok!(Assets::mint(RuntimeOrigin::signed(1), 1, 1, 100));
+		assert_eq!(Assets::account_balances(1), vec![(0, 100), (999, 100), (1, 100)]);
 	});
 }