feat(bank): Allow injectable restrictions on bank transfers

CHANGELOG.md

@@ -78,6 +78,7 @@ Ref: https://keepachangelog.com/en/1.0.0/
 * (cli) [#16209](https://github.com/cosmos/cosmos-sdk/pull/16209) Make `StartCmd` more customizable.
 * (types) [#16257](https://github.com/cosmos/cosmos-sdk/pull/16257) Allow setting the base denom in the denom registry.
 * (genutil) [#16046](https://github.com/cosmos/cosmos-sdk/pull/16046) Add "module-name" flag to genutil add-genesis-account to enable intializing module accounts at genesis.
+* (x/bank) [#14224](https://github.com/cosmos/cosmos-sdk/pull/14224) Allow injection of restrictions on transfers using `AppendSendRestriction` or `PrependSendRestriction`.
 
 ### Improvements
 

x/bank/README.md

@@ -236,8 +236,12 @@ accounts. The send keeper does not alter the total supply (mint or burn coins).
 type SendKeeper interface {
     ViewKeeper
 
-    InputOutputCoins(ctx context.Context, inputs types.Input, outputs []types.Output) error
-    SendCoins(ctx context.Context, fromAddr sdk.AccAddress, toAddr sdk.AccAddress, amt sdk.Coins) error
+    AppendSendRestriction(restriction SendRestrictionFn)
+    PrependSendRestriction(restriction SendRestrictionFn)
+    ClearSendRestriction()
+
+    InputOutputCoins(ctx context.Context, input types.Input, outputs []types.Output) error
+    SendCoins(ctx context.Context, fromAddr, toAddr sdk.AccAddress, amt sdk.Coins) error
 
     GetParams(ctx context.Context) types.Params
     SetParams(ctx context.Context, params types.Params) error

x/bank/keeper/export_test.go

@@ -0,0 +1,14 @@
+package keeper
+
+import "github.com/cosmos/cosmos-sdk/x/bank/types"
+
+// This file exists in the keeper package to expose some private things
+// for the purpose of testing in the keeper_test package.
+
+func (k BaseSendKeeper) SetSendRestriction(restriction types.SendRestrictionFn) {
+	k.sendRestriction.fn = restriction
+}
+
+func (k BaseSendKeeper) GetSendRestrictionFn() types.SendRestrictionFn {
+	return k.sendRestriction.fn
+}

x/bank/keeper/keeper.go

@@ -27,7 +27,7 @@ var _ Keeper = (*BaseKeeper)(nil)
 // between accounts.
 type Keeper interface {
 	SendKeeper
-	WithMintCoinsRestriction(MintingRestrictionFn) BaseKeeper
+	WithMintCoinsRestriction(types.MintingRestrictionFn) BaseKeeper
 
 	InitGenesis(context.Context, *types.GenesisState)
 	ExportGenesis(context.Context) *types.GenesisState
@@ -63,12 +63,10 @@ type BaseKeeper struct {
 	ak                     types.AccountKeeper
 	cdc                    codec.BinaryCodec
 	storeService           store.KVStoreService
-	mintCoinsRestrictionFn MintingRestrictionFn
+	mintCoinsRestrictionFn types.MintingRestrictionFn
 	logger                 log.Logger
 }
 
-type MintingRestrictionFn func(ctx context.Context, coins sdk.Coins) error
-
 // GetPaginatedTotalSupply queries for the supply, ignoring 0 coins, with a given pagination
 func (k BaseKeeper) GetPaginatedTotalSupply(ctx context.Context, pagination *query.PageRequest) (sdk.Coins, *query.PageResponse, error) {
 	results, pageResp, err := query.CollectionPaginate[string, math.Int](ctx, k.Supply, pagination)
@@ -109,7 +107,7 @@ func NewBaseKeeper(
 		ak:                     ak,
 		cdc:                    cdc,
 		storeService:           storeService,
-		mintCoinsRestrictionFn: func(ctx context.Context, coins sdk.Coins) error { return nil },
+		mintCoinsRestrictionFn: types.NoOpMintingRestrictionFn,
 		logger:                 logger,
 	}
 }
@@ -119,19 +117,8 @@ func NewBaseKeeper(
 // Previous restriction functions can be nested as such:
 //
 //	bankKeeper.WithMintCoinsRestriction(restriction1).WithMintCoinsRestriction(restriction2)
-func (k BaseKeeper) WithMintCoinsRestriction(check MintingRestrictionFn) BaseKeeper {
-	oldRestrictionFn := k.mintCoinsRestrictionFn
-	k.mintCoinsRestrictionFn = func(ctx context.Context, coins sdk.Coins) error {
-		err := check(ctx, coins)
-		if err != nil {
-			return err
-		}
-		err = oldRestrictionFn(ctx, coins)
-		if err != nil {
-			return err
-		}
-		return nil
-	}
+func (k BaseKeeper) WithMintCoinsRestriction(check types.MintingRestrictionFn) BaseKeeper {
+	k.mintCoinsRestrictionFn = check.Then(k.mintCoinsRestrictionFn)
 	return k
 }