Add low level traits to retrieve name, symbol, decimals and allowance in pallet-assets (#9757)

* Add ERC20 compatible trait to retrieve name, symbol, decimals and allowance

* delegate instead of spender

* Remove erc20 trait and divide it into lower level traits

* add import

* approvals and metadata depend on fungibles

Co-authored-by: Shawn Tabrizi <shawntabrizi@gmail.com>

substrate/frame/support/src/traits/tokens/fungibles.rs

@@ -25,7 +25,9 @@ use crate::dispatch::{DispatchError, DispatchResult};
 use sp_runtime::traits::Saturating;
 use sp_std::vec::Vec;
 
+pub mod approvals;
 mod balanced;
+pub mod metadata;
 pub use balanced::{Balanced, Unbalanced};
 mod imbalance;
 pub use imbalance::{CreditOf, DebtOf, HandleImbalanceDrop, Imbalance};

substrate/frame/support/src/traits/tokens/fungibles/approvals.rs

@@ -0,0 +1,43 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2019-2021 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.
+
+//! Inspect and Mutate traits for Asset approvals
+
+use crate::dispatch::DispatchResult;
+pub trait Inspect<AccountId>: super::Inspect<AccountId> {
+	// Check the amount approved by an owner to be spent by a delegate
+	fn allowance(asset: Self::AssetId, owner: &AccountId, delegate: &AccountId) -> Self::Balance;
+}
+
+pub trait Mutate<AccountId>: Inspect<AccountId> {
+	// Aprove a delegate account to spend an amount of tokens owned by an owner
+	fn approve(
+		asset: Self::AssetId,
+		owner: &AccountId,
+		delegate: &AccountId,
+		amount: Self::Balance,
+	) -> DispatchResult;
+
+	// Transfer from a delegate account an amount approved by the owner of the asset
+	fn transfer_from(
+		asset: Self::AssetId,
+		owner: &AccountId,
+		delegate: &AccountId,
+		dest: &AccountId,
+		amount: Self::Balance,
+	) -> DispatchResult;
+}

substrate/frame/support/src/traits/tokens/fungibles/metadata.rs

@@ -0,0 +1,41 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2019-2021 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.
+
+//! Inspect and Mutate traits for Asset metadata
+
+use crate::dispatch::DispatchResult;
+use sp_std::vec::Vec;
+
+pub trait Inspect<AccountId>: super::Inspect<AccountId> {
+	// Get name for an AssetId.
+	fn name(asset: Self::AssetId) -> Vec<u8>;
+	// Get symbol for an AssetId.
+	fn symbol(asset: Self::AssetId) -> Vec<u8>;
+	// Get decimals for an AssetId.
+	fn decimals(asset: Self::AssetId) -> u8;
+}
+
+pub trait Mutate<AccountId>: Inspect<AccountId> {
+	// Set name, symbol and decimals for a given assetId.
+	fn set(
+		asset: Self::AssetId,
+		from: &AccountId,
+		name: Vec<u8>,
+		symbol: Vec<u8>,
+		decimals: u8,
+	) -> DispatchResult;
+}