Move PalletVersion away from the crate version (#9165)

* Move `PalletVersion` away from the crate version

Before this pr, `PalletVersion` was referring to the crate version that
hosted the pallet. This pr introduces a custom `package.metadata.frame`
section in the `Cargo.toml` that can contain a `pallet-version` key
value pair. While the value is expected to be a valid u16. If this
key/value pair isn't given, the version is set to 1.

It also changes the `PalletVersion` declaration. We now only have one
`u16` that represents the version. Not a major/minor/patch version. As
the old `PalletVersion` was starting with the `u16` major, decoding the
old values will work.

* Overhaul the entire implementation

- Drop PalletVersion
- Introduce StorageVersion
- StorageVersion needs to be set in the crate and set for the macros
- Added migration

* Fix migrations

* Review feedback

* Remove unneeded dep

* remove pub consts

* Brings back logging and implements `GetStorageVersion`

* Return weight from migration

* Fmt and remove unused import

* Update frame/support/src/dispatch.rs

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

* Update frame/support/src/traits/metadata.rs

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

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

substrate/frame/support/test/tests/pallet.rs

@@ -19,9 +19,10 @@ use frame_support::{
 	dispatch::{Parameter, UnfilteredDispatchable},
 	storage::unhashed,
 	traits::{
-		GetCallName, GetPalletVersion, OnFinalize, OnGenesis, OnInitialize, OnRuntimeUpgrade,
+		GetCallName, GetStorageVersion, OnFinalize, OnGenesis, OnInitialize, OnRuntimeUpgrade,
+		PalletInfoAccess, StorageVersion,
 	},
-	weights::{DispatchClass, DispatchInfo, GetDispatchInfo, Pays},
+	weights::{DispatchClass, DispatchInfo, GetDispatchInfo, Pays, RuntimeDbWeight},
 };
 use sp_io::{
 	hashing::{blake2_128, twox_128, twox_64},
@@ -96,13 +97,15 @@ impl SomeAssociation2 for u64 {
 pub mod pallet {
 	use super::{
 		SomeAssociation1, SomeAssociation2, SomeType1, SomeType2, SomeType3, SomeType4, SomeType5,
-		SomeType6, SomeType7,
+		SomeType6, SomeType7, StorageVersion,
 	};
 	use frame_support::pallet_prelude::*;
 	use frame_system::pallet_prelude::*;
 
 	type BalanceOf<T> = <T as Config>::Balance;
 
+	pub(crate) const STORAGE_VERSION: StorageVersion = StorageVersion::new(10);
+
 	#[pallet::config]
 	pub trait Config: frame_system::Config
 	where
@@ -146,6 +149,7 @@ pub mod pallet {
 	#[pallet::pallet]
 	#[pallet::generate_store(pub(crate) trait Store)]
 	#[pallet::generate_storage_info]
+	#[pallet::storage_version(STORAGE_VERSION)]
 	pub struct Pallet<T>(_);
 
 	#[pallet::hooks]
@@ -896,12 +900,7 @@ fn pallet_hooks_expand() {
 		assert_eq!(AllPallets::on_initialize(1), 10);
 		AllPallets::on_finalize(1);
 
-		assert_eq!(pallet::Pallet::<Runtime>::storage_version(), None);
 		assert_eq!(AllPallets::on_runtime_upgrade(), 30);
-		assert_eq!(
-			pallet::Pallet::<Runtime>::storage_version(),
-			Some(pallet::Pallet::<Runtime>::current_version()),
-		);
 
 		assert_eq!(
 			frame_system::Pallet::<Runtime>::events()[0].event,
@@ -921,15 +920,60 @@ fn pallet_hooks_expand() {
 #[test]
 fn pallet_on_genesis() {
 	TestExternalities::default().execute_with(|| {
-		assert_eq!(pallet::Pallet::<Runtime>::storage_version(), None);
+		assert_eq!(pallet::Pallet::<Runtime>::on_chain_storage_version(), StorageVersion::new(0));
 		pallet::Pallet::<Runtime>::on_genesis();
 		assert_eq!(
-			pallet::Pallet::<Runtime>::storage_version(),
-			Some(pallet::Pallet::<Runtime>::current_version()),
+			pallet::Pallet::<Runtime>::current_storage_version(),
+			pallet::Pallet::<Runtime>::on_chain_storage_version(),
 		);
 	})
 }
 
+#[test]
+fn migrate_from_pallet_version_to_storage_version() {
+	const PALLET_VERSION_STORAGE_KEY_POSTFIX: &[u8] = b":__PALLET_VERSION__:";
+
+	fn pallet_version_key(name: &str) -> [u8; 32] {
+		let pallet_name = sp_io::hashing::twox_128(name.as_bytes());
+		let postfix = sp_io::hashing::twox_128(PALLET_VERSION_STORAGE_KEY_POSTFIX);
+
+		let mut final_key = [0u8; 32];
+		final_key[..16].copy_from_slice(&pallet_name);
+		final_key[16..].copy_from_slice(&postfix);
+
+		final_key
+	}
+
+	TestExternalities::default().execute_with(|| {
+		// Insert some fake pallet versions
+		sp_io::storage::set(&pallet_version_key(Example::name()), &[1, 2, 3]);
+		sp_io::storage::set(&pallet_version_key(Example2::name()), &[1, 2, 3]);
+		sp_io::storage::set(&pallet_version_key(System::name()), &[1, 2, 3]);
+
+		// Check that everyone currently is at version 0
+		assert_eq!(Example::on_chain_storage_version(), StorageVersion::new(0));
+		assert_eq!(Example2::on_chain_storage_version(), StorageVersion::new(0));
+		assert_eq!(System::on_chain_storage_version(), StorageVersion::new(0));
+
+		let db_weight = RuntimeDbWeight { read: 0, write: 5 };
+		let weight = frame_support::migrations::migrate_from_pallet_version_to_storage_version::<
+			AllPalletsWithSystem,
+		>(&db_weight);
+
+		// 3 pallets, 2 writes and every write costs 5 weight.
+		assert_eq!(3 * 2 * 5, weight);
+
+		// All pallet versions should be removed
+		assert!(sp_io::storage::get(&pallet_version_key(Example::name())).is_none());
+		assert!(sp_io::storage::get(&pallet_version_key(Example2::name())).is_none());
+		assert!(sp_io::storage::get(&pallet_version_key(System::name())).is_none());
+
+		assert_eq!(Example::on_chain_storage_version(), pallet::STORAGE_VERSION);
+		assert_eq!(Example2::on_chain_storage_version(), StorageVersion::new(0));
+		assert_eq!(System::on_chain_storage_version(), StorageVersion::new(0));
+	});
+}
+
 #[test]
 fn metadata() {
 	use codec::{Decode, Encode};