fix: keep the balance query endpoint compatible with legacy blocks (b…

…ackport cosmos#13301) (cosmos#13318)

* fix: keep the balance query endpoint compatible with legacy blocks (cosmos#13301)

* keep the balance query endpoint compatible with legacy blocks

Closes: cosmos#13296

A temporary solution before the proxy tool developed, since the balance endpoint is too important.

* Update CHANGELOG.md

* Apply suggestions from code review

Co-authored-by: Julien Robert <julien@rbrt.fr>
Co-authored-by: Marko <marbar3778@yahoo.com>
(cherry picked from commit 6c4f94b)

# Conflicts:
#	CHANGELOG.md
#	x/bank/keeper/view.go

* Apply suggestions from code review

* fix lint

Co-authored-by: yihuang <huang@crypto.com>
Co-authored-by: Julien Robert <julien@rbrt.fr>

CHANGELOG.md

@@ -53,6 +53,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (x/group) [#13214](https://github.com/cosmos/cosmos-sdk/pull/13214) Add `withdraw-proposal` command to group module's CLI transaction commands.
 * (x/auth) [#13048](https://github.com/cosmos/cosmos-sdk/pull/13048) Add handling of AccountNumberStoreKeyPrefix to the simulation decoder.
 * (simapp) [#13108](https://github.com/cosmos/cosmos-sdk/pull/13108) Call `SetIAVLCacheSize` with the configured value in simapp.
+* [#13318](https://github.com/cosmos/cosmos-sdk/pull/13318) Keep the balance query endpoint compatible with legacy blocks
 
 ### Bug Fixes
 

x/bank/keeper/grpc_query.go

@@ -3,7 +3,6 @@ package keeper
 import (
 	"context"
 
-	"cosmossdk.io/math"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 
@@ -88,11 +87,12 @@ func (k BaseKeeper) SpendableBalances(ctx context.Context, req *types.QuerySpend
 	}
 
 	pageRes, err := query.Paginate(accountStore, req.Pagination, func(key, value []byte) error {
-		var amount math.Int
-		if err := amount.Unmarshal(value); err != nil {
+		denom := string(key)
+		balance, err := UnmarshalBalanceCompat(k.cdc, value, denom)
+		if err != nil {
 			return err
 		}
-		balances = append(balances, result)
+		balances = append(balances, balance)
 		return nil
 	})
 	if err != nil {

x/bank/keeper/view.go

@@ -134,12 +134,15 @@ func (k BaseViewKeeper) GetAccountsBalances(ctx context.Context) []types.Balance
 
 // GetBalance returns the balance of a specific denomination for a given account
 // by address.
-func (k BaseViewKeeper) GetBalance(ctx context.Context, addr sdk.AccAddress, denom string) sdk.Coin {
-	amt, err := k.Balances.Get(ctx, collections.Join(addr, denom))
+func (k BaseViewKeeper) GetBalance(ctx sdk.Context, addr sdk.AccAddress, denom string) sdk.Coin {
+	accountStore := k.getAccountStore(ctx, addr)
+	bz := accountStore.Get([]byte(denom))
+	balance, err := UnmarshalBalanceCompat(k.cdc, bz, denom)
 	if err != nil {
-		return sdk.NewCoin(denom, math.ZeroInt())
+		panic(err)
 	}
-	return sdk.NewCoin(denom, amt)
+
+	return balance
 }
 
 // IterateAccountBalances iterates over the balances of a single account and
@@ -152,12 +155,13 @@ func (k BaseViewKeeper) IterateAccountBalances(ctx sdk.Context, addr sdk.AccAddr
 	defer iterator.Close()
 
 	for ; iterator.Valid(); iterator.Next() {
-		var amount math.Int
-		if err := amount.Unmarshal(iterator.Value()); err != nil {
+		denom := string(iterator.Key())
+		balance, err := UnmarshalBalanceCompat(k.cdc, iterator.Value(), denom)
+		if err != nil {
 			panic(err)
 		}
 
-		if cb(sdk.NewCoin(string(iterator.Key()), amount)) {
+		if cb(balance) {
 			break
 		}
 	}
@@ -182,12 +186,12 @@ func (k BaseViewKeeper) IterateAllBalances(ctx sdk.Context, cb func(sdk.AccAddre
 			panic(err)
 		}
 
-		var amount math.Int
-		if err := amount.Unmarshal(iterator.Value()); err != nil {
+		balance, err := UnmarshalBalanceCompat(k.cdc, iterator.Value(), denom)
+		if err != nil {
 			panic(err)
 		}
 
-		if cb(address, sdk.NewCoin(denom, amount)) {
+		if cb(address, balance) {
 			break
 		}
 	}
@@ -276,3 +280,35 @@ func (k BaseViewKeeper) ValidateBalance(ctx context.Context, addr sdk.AccAddress
 
 	return nil
 }
+
+// getAccountStore gets the account store of the given address.
+func (k BaseViewKeeper) getAccountStore(ctx sdk.Context, addr sdk.AccAddress) prefix.Store {
+	store := ctx.KVStore(k.storeKey)
+	return prefix.NewStore(store, types.CreateAccountBalancesPrefix(addr))
+}
+
+// getDenomAddressPrefixStore returns a prefix store that acts as a reverse index
+// between a denomination and account balance for that denomination.
+func (k BaseViewKeeper) getDenomAddressPrefixStore(ctx sdk.Context, denom string) prefix.Store {
+	return prefix.NewStore(ctx.KVStore(k.storeKey), types.CreateDenomAddressPrefix(denom))
+}
+
+// UnmarshalBalanceCompat unmarshal balance amount from storage, it's backward-compatible with the legacy format.
+func UnmarshalBalanceCompat(cdc codec.BinaryCodec, bz []byte, denom string) (sdk.Coin, error) {
+	amount := math.ZeroInt()
+	if bz == nil {
+		return sdk.NewCoin(denom, amount), nil
+	}
+
+	if err := amount.Unmarshal(bz); err != nil {
+		// try to unmarshal with the legacy format.
+		var balance sdk.Coin
+		if cdc.Unmarshal(bz, &balance) != nil {
+			// return with the original error
+			return sdk.Coin{}, err
+		}
+		return balance, nil
+	}
+
+	return sdk.NewCoin(denom, amount), nil
+}