migrate pallet-elections-phragmen to attribute macros (#8044)

* All done

* Fix benchmarks

* Apply suggestions from code review

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* Fix metadata.

* Fix build

* Add migrations

* Fix

* Update frame/elections-phragmen/src/migrations/v4.rs

* Better migeation test

* More test

* Fix warn

* Update frame/elections-phragmen/src/lib.rs

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

* Fix test

* early exit

* Fix

* Fix build

Co-authored-by: Guillaume Thiolliere <gui.thiolliere@gmail.com>

substrate/frame/elections-phragmen/CHANGELOG.md

@@ -4,7 +4,18 @@ All notable changes to this crate will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this crate adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
-## [3.0.0] - UNRELEASED
+## [4.0.0] - UNRELEASED
+
+### Added
+
+### Changed
+\[**Needs Migration**\] [migrate pallet-elections-phragmen to attribute macros](https://github.com/paritytech/substrate/pull/8044)
+
+### Fixed
+
+### Security
+
+## [3.0.0]
 
 ### Added
 [Add slashing events to elections-phragmen](https://github.com/paritytech/substrate/pull/7543)

substrate/frame/elections-phragmen/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "pallet-elections-phragmen"
-version = "3.0.0"
+version = "4.0.0"
 authors = ["Parity Technologies <admin@parity.io>"]
 edition = "2018"
 license = "Apache-2.0"
@@ -16,14 +16,15 @@ targets = ["x86_64-unknown-linux-gnu"]
 codec = { package = "parity-scale-codec", version = "2.0.0", default-features = false, features = ["derive"] }
 sp-runtime = { version = "3.0.0", default-features = false, path = "../../primitives/runtime" }
 sp-npos-elections = { version = "3.0.0", default-features = false, path = "../../primitives/npos-elections" }
+sp-io = { version = "3.0.0", default-features = false, path = "../../primitives/io" }
 frame-support = { version = "3.0.0", default-features = false, path = "../support" }
 frame-system = { version = "3.0.0", default-features = false, path = "../system" }
 sp-std = { version = "3.0.0", default-features = false, path = "../../primitives/std" }
+sp-core = { version = "3.0.0", default-features = false, path = "../../primitives/core" }
 frame-benchmarking = { version = "3.1.0", default-features = false, path = "../benchmarking", optional = true }
 log = { version = "0.4.14", default-features = false }
 
 [dev-dependencies]
-sp-io = { version = "3.0.0", path = "../../primitives/io" }
 hex-literal = "0.3.1"
 pallet-balances = { version = "3.0.0", path = "../balances" }
 sp-core = { version = "3.0.0", path = "../../primitives/core" }
@@ -38,6 +39,8 @@ std = [
 	"sp-npos-elections/std",
 	"frame-system/std",
 	"sp-std/std",
+	"sp-io/std",
+	"sp-core/std",
 	"log/std",
 ]
 runtime-benchmarks = [

substrate/frame/elections-phragmen/src/benchmarking.rs

@@ -23,9 +23,9 @@ use super::*;
 
 use frame_system::RawOrigin;
 use frame_benchmarking::{benchmarks, account, whitelist, impl_benchmark_test_suite};
-use frame_support::traits::OnInitialize;
+use frame_support::{traits::OnInitialize, dispatch::DispatchResultWithPostInfo};
 
-use crate::Module as Elections;
+use crate::Pallet as Elections;
 
 const BALANCE_FACTOR: u32 = 250;
 const MAX_VOTERS: u32 = 500;
@@ -87,11 +87,12 @@ fn submit_candidates_with_self_vote<T: Config>(c: u32, prefix: &'static str)
 	Ok(candidates)
 }
 
-
 /// Submit one voter.
-fn submit_voter<T: Config>(caller: T::AccountId, votes: Vec<T::AccountId>, stake: BalanceOf<T>)
-	-> frame_support::dispatch::DispatchResult
-{
+fn submit_voter<T: Config>(
+	caller: T::AccountId,
+	votes: Vec<T::AccountId>,
+	stake: BalanceOf<T>,
+) -> DispatchResultWithPostInfo {
 	<Elections<T>>::vote(RawOrigin::Signed(caller).into(), votes, stake)
 }
 

substrate/frame/elections-phragmen/src/migrations/mod.rs

@@ -0,0 +1,23 @@
+// This file is part of Substrate.
+
+// Copyright (C) 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.
+
+//! All migrations of this pallet.
+
+/// Version 3.
+pub mod v3;
+/// Version 4.
+pub mod v4;

substrate/frame/elections-phragmen/src/migrations/v4.rs

@@ -0,0 +1,110 @@
+// This file is part of Substrate.
+
+// Copyright (C) 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.
+
+//! Migrations to version [`4.0.0`], as denoted by the changelog.
+
+use frame_support::{
+	weights::Weight,
+	traits::{GetPalletVersion, PalletVersion, Get},
+};
+
+/// The old prefix.
+pub const OLD_PREFIX: &[u8] = b"PhragmenElection";
+
+/// Migrate the entire storage of this pallet to a new prefix.
+///
+/// This new prefix must be the same as the one set in construct_runtime. For safety, use
+/// `PalletInfo` to get it, as:
+/// `<Runtime as frame_system::Config>::PalletInfo::name::<ElectionsPhragmenPallet>`.
+///
+/// The old storage prefix, `PhragmenElection` is hardcoded in the migration code.
+pub fn migrate<
+	T: frame_system::Config,
+	P: GetPalletVersion,
+	N: AsRef<str>,
+>(new_pallet_name: N) -> Weight {
+	if new_pallet_name.as_ref().as_bytes() == OLD_PREFIX {
+		log::info!(
+			target: "runtime::elections-phragmen",
+			"New pallet name is equal to the old prefix. No migration needs to be done.",
+		);
+		return 0;
+	}
+	let maybe_storage_version = <P as GetPalletVersion>::storage_version();
+	log::info!(
+		target: "runtime::elections-phragmen",
+		"Running migration to v4 for elections-phragmen with storage version {:?}",
+		maybe_storage_version,
+	);
+
+	match maybe_storage_version {
+		Some(storage_version) if storage_version <= PalletVersion::new(3, 0, 0) => {
+			log::info!("new prefix: {}", new_pallet_name.as_ref());
+			frame_support::storage::migration::move_pallet(
+				OLD_PREFIX,
+				new_pallet_name.as_ref().as_bytes(),
+			);
+			<T as frame_system::Config>::BlockWeights::get().max_block
+		}
+		_ => {
+			log::warn!(
+				target: "runtime::elections-phragmen",
+				"Attempted to apply migration to v4 but failed because storage version is {:?}",
+				maybe_storage_version,
+			);
+			0
+		},
+	}
+}
+
+/// Some checks prior to migration. This can be linked to
+/// [`frame_support::traits::OnRuntimeUpgrade::pre_upgrade`] for further testing.
+///
+/// Panics if anything goes wrong.
+pub fn pre_migration<P: GetPalletVersion, N: AsRef<str>>(new: N) {
+	let new = new.as_ref();
+	log::info!("pre-migration elections-phragmen test with new = {}", new);
+
+	// the next key must exist, and start with the hash of `OLD_PREFIX`.
+	let next_key = sp_io::storage::next_key(OLD_PREFIX).unwrap();
+	assert!(next_key.starts_with(&sp_io::hashing::twox_128(OLD_PREFIX)));
+
+	// ensure nothing is stored in the new prefix.
+	assert!(
+		sp_io::storage::next_key(new.as_bytes()).map_or(
+			// either nothing is there
+			true,
+			// or we ensure that it has no common prefix with twox_128(new).
+			|next_key| !next_key.starts_with(&sp_io::hashing::twox_128(new.as_bytes()))
+		),
+		"unexpected next_key({}) = {:?}",
+		new,
+		sp_core::hexdisplay::HexDisplay::from(&sp_io::storage::next_key(new.as_bytes()).unwrap())
+	);
+	// ensure storage version is 3.
+	assert!(<P as GetPalletVersion>::storage_version().unwrap().major == 3);
+}
+
+/// Some checks for after migration. This can be linked to
+/// [`frame_support::traits::OnRuntimeUpgrade::post_upgrade`] for further testing.
+///
+/// Panics if anything goes wrong.
+pub fn post_migration<P : GetPalletVersion>() {
+	log::info!("post-migration elections-phragmen");
+	// ensure we've been updated to v4 by the automatic write of crate version -> storage version.
+	assert!(<P as GetPalletVersion>::storage_version().unwrap().major == 4);
+}