Migrate Weights properly to v2 (#1722)

* Migrate Weights properly to v2

* Add missing on_runtime_upgrade implementation

* Fix benchmarks

* Apply suggestions from code review

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

* cargo fmt

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

pallets/dmp-queue/src/migration.rs

@@ -0,0 +1,101 @@
+// Copyright 2022 Parity Technologies (UK) Ltd.
+// This file is part of Polkadot.
+
+// Polkadot is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Polkadot is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Polkadot.  If not, see <http://www.gnu.org/licenses/>.
+
+//! A module that is responsible for migration of storage.
+
+use crate::{Config, Pallet, Store};
+use frame_support::{
+	pallet_prelude::*,
+	traits::StorageVersion,
+	weights::{constants::WEIGHT_PER_MILLIS, Weight},
+};
+use xcm::latest::Weight as XcmWeight;
+
+/// The current storage version.
+pub const STORAGE_VERSION: StorageVersion = StorageVersion::new(1);
+
+/// Migrates the pallet storage to the most recent version, checking and setting the
+/// `StorageVersion`.
+pub fn migrate_to_latest<T: Config>() -> Weight {
+	let mut weight = T::DbWeight::get().reads(1);
+
+	if StorageVersion::get::<Pallet<T>>() == 0 {
+		weight += migrate_to_v1::<T>();
+		StorageVersion::new(1).put::<Pallet<T>>();
+	}
+
+	weight
+}
+
+mod v0 {
+	use super::*;
+	use codec::{Decode, Encode};
+
+	#[derive(Decode, Encode, Debug)]
+	pub struct ConfigData {
+		pub max_individual: XcmWeight,
+	}
+
+	impl Default for ConfigData {
+		fn default() -> Self {
+			ConfigData { max_individual: 10u64 * WEIGHT_PER_MILLIS.ref_time() }
+		}
+	}
+}
+
+/// Migrates `QueueConfigData` from v1 (using only reference time weights) to v2 (with
+/// 2D weights).
+///
+/// NOTE: Only use this function if you know what you're doing. Default to using
+/// `migrate_to_latest`.
+pub fn migrate_to_v1<T: Config>() -> Weight {
+	let translate = |pre: v0::ConfigData| -> super::ConfigData {
+		super::ConfigData { max_individual: Weight::from_ref_time(pre.max_individual) }
+	};
+
+	if let Err(_) = <Pallet<T> as Store>::Configuration::translate(|pre| pre.map(translate)) {
+		log::error!(
+			target: "dmp_queue",
+			"unexpected error when performing translation of the QueueConfig type during storage upgrade to v2"
+		);
+	}
+
+	T::DbWeight::get().reads_writes(1, 1)
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use crate::tests::{new_test_ext, Test};
+
+	#[test]
+	fn test_migration_to_v1() {
+		let v0 = v0::ConfigData { max_individual: 30_000_000_000 };
+
+		new_test_ext().execute_with(|| {
+			frame_support::storage::unhashed::put_raw(
+				&crate::Configuration::<Test>::hashed_key(),
+				&v0.encode(),
+			);
+
+			migrate_to_v1::<Test>();
+
+			let v1 = crate::Configuration::<Test>::get();
+
+			assert_eq!(v0.max_individual, v1.max_individual.ref_time());
+		});
+	}
+}