Implement fungible::* for Balances

bin/node/runtime/src/lib.rs

@@ -1042,6 +1042,8 @@ impl pallet_assets::Config for Runtime {
 	type MetadataDepositPerByte = MetadataDepositPerByte;
 	type ApprovalDeposit = ApprovalDeposit;
 	type StringLimit = StringLimit;
+	type Freezer = ();
+	type Extra = ();
 	type WeightInfo = pallet_assets::weights::SubstrateWeight<Runtime>;
 }
 

frame/assets/src/extra_mutator.rs

@@ -0,0 +1,105 @@
+// This file is part of Substrate.
+
+// Copyright (C) 2017-2021 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.
+
+//! Datatype for easy mutation of the extra "sidecar" data.
+
+use super::*;
+
+/// A mutator type allowing inspection and possible modification of the extra "sidecar" data.
+///
+/// This may be used as a `Deref` for the pallet's extra data. If mutated (using `DerefMut`), then
+/// any uncommitted changes (see `commit` function) will be automatically committed to storage when
+/// dropped. Changes, even after committed, may be reverted to their original values with the
+/// `revert` function.
+pub struct ExtraMutator<T: Config> {
+	id: T::AssetId,
+	who: T::AccountId,
+	original: T::Extra,
+	pending: Option<T::Extra>,
+}
+
+impl<T: Config> Drop for ExtraMutator<T> {
+	fn drop(&mut self) {
+		debug_assert!(self.commit().is_ok(), "attempt to write to non-existent asset account");
+	}
+}
+
+impl<T: Config> sp_std::ops::Deref for ExtraMutator<T> {
+	type Target = T::Extra;
+	fn deref(&self) -> &T::Extra {
+		match self.pending {
+			Some(ref value) => value,
+			None => &self.original,
+		}
+	}
+}
+
+impl<T: Config> sp_std::ops::DerefMut for ExtraMutator<T> {
+	fn deref_mut(&mut self) -> &mut T::Extra {
+		if self.pending.is_none() {
+			self.pending = Some(self.original.clone());
+		}
+		self.pending.as_mut().unwrap()
+	}
+}
+
+impl<T: Config> ExtraMutator<T> {
+	pub(super) fn maybe_new(id: T::AssetId, who: impl sp_std::borrow::Borrow<T::AccountId>)
+		-> Option<ExtraMutator<T>>
+	{
+		if Account::<T>::contains_key(id, who.borrow()) {
+			Some(ExtraMutator::<T> {
+				id,
+				who: who.borrow().clone(),
+				original: Account::<T>::get(id, who.borrow()).extra,
+				pending: None,
+			})
+		} else {
+			None
+		}
+	}
+
+
+	/// Commit any changes to storage.
+	pub fn commit(&mut self) -> Result<(), ()> {
+		if let Some(extra) = self.pending.take() {
+			Account::<T>::try_mutate_exists(self.id, self.who.borrow(), |maybe_account|
+				if let Some(ref mut account) = maybe_account {
+					account.extra = extra;
+					Ok(())
+				} else {
+					Err(())
+				}
+			)
+		} else {
+			Ok(())
+		}
+	}
+
+	/// Revert any changes, even those already committed by `self` and drop self.
+	pub fn revert(mut self) -> Result<(), ()> {
+		self.pending = None;
+		Account::<T>::try_mutate_exists(self.id, self.who.borrow(), |maybe_account|
+			if let Some(ref mut account) = maybe_account {
+				account.extra = self.original.clone();
+				Ok(())
+			} else {
+				Err(())
+			}
+		)
+	}
+}