add indices migration and adjust it for frozen indices

based on paritytech#5870

frame/indices/src/lib.rs

@@ -28,14 +28,15 @@ use sp_runtime::traits::{
 use frame_support::{Parameter, decl_module, decl_error, decl_event, decl_storage, ensure};
 use frame_support::dispatch::DispatchResult;
 use frame_support::traits::{Currency, ReservableCurrency, Get, BalanceStatus::Reserved};
-use frame_support::weights::constants::WEIGHT_PER_MICROS;
+use frame_support::weights::{constants::WEIGHT_PER_MICROS, Weight};
 use frame_system::{ensure_signed, ensure_root};
 use self::address::Address as RawAddress;
 
 mod mock;
 pub mod address;
 mod tests;
 mod benchmarking;
+pub mod migration;
 
 pub type Address<T> = RawAddress<<T as frame_system::Trait>::AccountId, <T as Trait>::AccountIndex>;
 type BalanceOf<T> = <<T as Trait>::Currency as Currency<<T as frame_system::Trait>::AccountId>>::Balance;
@@ -104,6 +105,10 @@ decl_module! {
 	pub struct Module<T: Trait> for enum Call where origin: T::Origin, system = frame_system {
 		fn deposit_event() = default;
 
+		fn on_runtime_upgrade() -> Weight {
+			migration::migrate_enum_set::<T>()
+		}
+
 		/// Assign an previously unassigned index.
 		///
 		/// Payment: `Deposit` is reserved from the sender account.

frame/indices/src/migration.rs

@@ -0,0 +1,51 @@
+use super::*;
+use frame_support::weights::Weight;
+use sp_runtime::traits::One;
+
+mod deprecated {
+    use crate::Trait;
+    use frame_support::{decl_module, decl_storage};
+    use sp_std::prelude::*;
+
+    decl_storage! {
+        trait Store for Module<T: Trait> as Indices {
+            /// The next free enumeration set.
+            pub NextEnumSet get(fn next_enum_set): T::AccountIndex;
+
+            /// The enumeration sets.
+            pub EnumSet get(fn enum_set): map hasher(opaque_blake2_256) T::AccountIndex => Vec<T::AccountId>;
+        }
+    }
+    decl_module! {
+        pub struct Module<T: Trait> for enum Call where origin: T::Origin { }
+    }
+}
+
+// Taken from a migration removal PR [here](https://github.com/paritytech/substrate/pull/5870/files#diff-12b2ce0dfddc1915cd81a902d368c2e7L246)
+pub fn migrate_enum_set<T: Trait>() -> Weight {
+    if deprecated::NextEnumSet::<T>::exists() {
+        // migrations need doing.
+        let set_count = deprecated::NextEnumSet::<T>::take();
+        let set_size: T::AccountIndex = 64.into();
+
+        let mut set_index: T::AccountIndex = Zero::zero();
+        while set_index < set_count {
+            if !deprecated::EnumSet::<T>::contains_key(&set_index) {
+                break;
+            }
+            let accounts = deprecated::EnumSet::<T>::take(&set_index);
+            for (item_index, target) in accounts.into_iter().enumerate() {
+                if target != T::AccountId::default() && !T::Currency::total_balance(&target).is_zero() {
+                    let index = set_index * set_size + T::AccountIndex::from(item_index as u32);
+                    // We need to add `false` to indicate the index is not frozen.
+                    // See the [frozen indices PR](https://github.com/paritytech/substrate/pull/6307/)
+                    Accounts::<T>::insert(index, (target, BalanceOf::<T>::zero(), false));
+                }
+            }
+            set_index += One::one();
+        }
+        T::MaximumBlockWeight::get()
+    } else {
+        0
+    }
+}