Storage migration of elections-phragmen

srml/elections-phragmen/Cargo.toml

@@ -5,27 +5,24 @@ authors = ["Parity Technologies <[email protected]>"]
 edition = "2018"
 
 [dependencies]
-serde = { version = "1.0.101", optional = true }
 codec = { package = "parity-scale-codec", version = "1.0.0", default-features = false, features = ["derive"] }
-primitives = { package = "substrate-primitives", path = "../../core/primitives", default-features = false }
-runtime_io = { package = "sr-io", path = "../../core/sr-io", default-features = false }
 sr-primitives = { path = "../../core/sr-primitives", default-features = false }
 phragmen = { package = "substrate-phragmen", path = "../../core/phragmen", default-features = false }
 srml-support = { path = "../support", default-features = false }
 system = { package = "srml-system", path = "../system", default-features = false }
 rstd = { package = "sr-std", path = "../../core/sr-std", default-features = false }
 
 [dev-dependencies]
+runtime_io = { package = "sr-io", path = "../../core/sr-io" }
 hex-literal = "0.2.1"
 balances = { package = "srml-balances", path = "../balances" }
+primitives = { package = "substrate-primitives", path = "../../core/primitives" }
+serde = { version = "1.0.101" }
 
 [features]
 default = ["std"]
 std = [
  "codec/std",
- "primitives/std",
- "serde",
- "runtime_io/std",
  "srml-support/std",
  "sr-primitives/std",
  "phragmen/std",

srml/elections-phragmen/src/lib.rs

@@ -77,10 +77,12 @@
 #![cfg_attr(not(feature = "std"), no_std)]
 
 use rstd::prelude::*;
+use codec::Decode;
 use sr_primitives::{print, traits::{Zero, StaticLookup, Bounded, Convert}};
 use sr_primitives::weights::SimpleDispatchInfo;
 use srml_support::{
  decl_storage, decl_event, ensure, decl_module, dispatch,
+ storage::unhashed,
  traits::{
  Currency, Get, LockableCurrency, LockIdentifier, ReservableCurrency, WithdrawReasons,
  ChangeMembers, OnUnbalanced, WithdrawReason
@@ -159,6 +161,11 @@ decl_storage! {
  /// The present candidate list. Sorted based on account id. A current member can never enter
  /// this vector and is always implicitly assumed to be a candidate.
  pub Candidates get(fn candidates): Vec<T::AccountId>;
+
+ /// Has the storage format been updated?
+ /// NOTE: Only use and set to false if you have used an early version of this module. Should
+ /// be set to true otherwise.
+ DidMigrate: bool;
  }
 }
 
@@ -373,6 +380,10 @@ decl_module! {
 
  /// What to do at the end of each block. Checks if an election needs to happen or not.
  fn on_initialize(n: T::BlockNumber) {
+ if !DidMigrate::exists() {
+ DidMigrate::put(true);
+ Self::do_migrate();
+ }
  if let Err(e) = Self::end_block(n) {
  print("Guru meditation");
  print(e);
@@ -626,6 +637,32 @@ impl<T: Trait> Module<T> {
 
  ElectionRounds::mutate(|v| *v += 1);
  }
+
+ /// Perform the storage update needed to migrate the module from the initial version of the
+ /// storage.
+ ///
+ /// If decoding the old storage fails in any way, the consequence is that we start with an empty
+ /// set.
+ fn do_migrate() {
+ // old storage format.
+ let old_members: Vec<T::AccountId> = unhashed::get_raw(&<Members<T>>::hashed_key())
+ .and_then(|bytes| Decode::decode(&mut &*bytes).ok()).unwrap_or_default();
+ let old_runners: Vec<T::AccountId> = unhashed::get_raw(&<RunnersUp<T>>::hashed_key())
+ .and_then(|bytes| Decode::decode(&mut &*bytes).ok()).unwrap_or_default();
+
+ // new storage format.
+ let new_runners: Vec<(T::AccountId, BalanceOf<T>)> = old_runners
+ .into_iter()
+ .map(|r| (r, Zero::zero()))
+ .collect();
+ let new_members: Vec<(T::AccountId, BalanceOf<T>)> = old_members
+ .into_iter()
+ .map(|r| (r, Zero::zero()))
+ .collect();
+
+ <Members<T>>::put(new_members);
+ <RunnersUp<T>>::put(new_runners);
+ }
 }
 
 #[cfg(test)]
@@ -636,7 +673,7 @@ mod tests {
  use primitives::H256;
  use sr_primitives::{
  Perbill, testing::Header, BuildStorage,
- traits::{BlakeTwo256, IdentityLookup, Block as BlockT},
+ traits::{OnInitialize, BlakeTwo256, IdentityLookup, Block as BlockT},
  };
  use crate as elections;
 
@@ -825,6 +862,30 @@ mod tests {
  lock.amount
  }
 
+ #[test]
+ fn temp_migration_works() {
+ ExtBuilder::default().build().execute_with(|| {
+ use srml_support::storage::unhashed;
+ use codec::Encode;
+
+ let old_members = vec![1u64, 2];
+ let old_runners = vec![3u64];
+
+ let members_key = <Members<Test>>::hashed_key();
+ let runners_key = <RunnersUp<Test>>::hashed_key();
+
+ unhashed::put_raw(&members_key, &old_members.encode()[..]);
+ unhashed::put_raw(&runners_key, &old_runners.encode()[..]);
+
+ assert_eq!(DidMigrate::get(), false);
+ <Elections as OnInitialize<u64>>::on_initialize(1);
+ assert_eq!(DidMigrate::get(), true);
+
+ assert_eq!(Elections::members(), vec![(1, 0), (2, 0)]);
+ assert_eq!(Elections::runners_up(), vec![(3, 0)]);
+ });
+ }
+
  #[test]
  fn params_should_work() {
  ExtBuilder::default().build().execute_with(|| {