Add StorageNoopGuard (paritytech#12163)

* Add StorageNoopGuard

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Fix import

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Fix feature gate

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Fix feature gate

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* Use sp-std

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

frame/support/src/lib.rs

@@ -93,6 +93,8 @@ pub mod unsigned {
  };
 }
 
+#[cfg(any(feature = "std", feature = "runtime-benchmarks", test))]
+pub use self::storage::storage_noop_guard::StorageNoopGuard;
 pub use self::{
  dispatch::{Callable, Parameter},
  hash::{

frame/support/src/storage/mod.rs

@@ -46,6 +46,7 @@ pub mod child;
 pub mod generator;
 pub mod hashed;
 pub mod migration;
+pub mod storage_noop_guard;
 pub mod transactional;
 pub mod types;
 pub mod unhashed;

frame/support/src/storage/storage_noop_guard.rs

@@ -0,0 +1,114 @@
+// 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.
+
+// Feature gated since it can panic.
+#![cfg(any(feature = "std", feature = "runtime-benchmarks", test))]
+
+//! Contains the [`crate::StorageNoopGuard`] for conveniently asserting
+//! that no storage mutation has been made by a whole code block.
+
+/// Asserts that no storage changes took place between con- and destruction of [`Self`].
+///
+/// This is easier than wrapping the whole code-block inside a `assert_storage_noop!`.
+///
+/// # Example
+///
+/// ```should_panic
+/// use frame_support::{StorageNoopGuard, storage::unhashed::put};
+///
+/// sp_io::TestExternalities::default().execute_with(|| {
+/// let _guard = frame_support::StorageNoopGuard::default();
+/// put(b"key", b"value");
+/// // Panics since there are storage changes.
+/// });
+/// ```
+#[must_use]
+pub struct StorageNoopGuard(sp_std::vec::Vec<u8>);
+
+impl Default for StorageNoopGuard {
+ fn default() -> Self {
+ Self(frame_support::storage_root(frame_support::StateVersion::V1))
+ }
+}
+
+impl Drop for StorageNoopGuard {
+ fn drop(&mut self) {
+ // No need to double panic, eg. inside a test assertion failure.
+ if sp_std::thread::panicking() {
+ return
+ }
+ assert_eq!(
+ frame_support::storage_root(frame_support::StateVersion::V1),
+ self.0,
+ "StorageNoopGuard detected wrongful storage changes.",
+ );
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use super::*;
+ use sp_io::TestExternalities;
+
+ #[test]
+ #[should_panic(expected = "StorageNoopGuard detected wrongful storage changes.")]
+ fn storage_noop_guard_panics_on_changed() {
+ TestExternalities::default().execute_with(|| {
+ let _guard = StorageNoopGuard::default();
+ frame_support::storage::unhashed::put(b"key", b"value");
+ });
+ }
+
+ #[test]
+ fn storage_noop_guard_works_on_unchanged() {
+ TestExternalities::default().execute_with(|| {
+ let _guard = StorageNoopGuard::default();
+ frame_support::storage::unhashed::put(b"key", b"value");
+ frame_support::storage::unhashed::kill(b"key");
+ });
+ }
+
+ #[test]
+ #[should_panic(expected = "StorageNoopGuard detected wrongful storage changes.")]
+ fn storage_noop_guard_panics_on_early_drop() {
+ TestExternalities::default().execute_with(|| {
+ let guard = StorageNoopGuard::default();
+ frame_support::storage::unhashed::put(b"key", b"value");
+ sp_std::mem::drop(guard);
+ frame_support::storage::unhashed::kill(b"key");
+ });
+ }
+
+ #[test]
+ fn storage_noop_guard_works_on_changed_forget() {
+ TestExternalities::default().execute_with(|| {
+ let guard = StorageNoopGuard::default();
+ frame_support::storage::unhashed::put(b"key", b"value");
+ sp_std::mem::forget(guard);
+ });
+ }
+
+ #[test]
+ #[should_panic(expected = "Something else")]
+ fn storage_noop_guard_does_not_double_panic() {
+ TestExternalities::default().execute_with(|| {
+ let _guard = StorageNoopGuard::default();
+ frame_support::storage::unhashed::put(b"key", b"value");
+ panic!("Something else");
+ });
+ }
+}