baseapp: fix sender events accumulation

closes: #6306
original PR: #6307

CHANGELOG.md

@@ -84,6 +84,7 @@ respectively, and the latter defines the height interval in which versions are d
 **Note, there are some client-facing API breaking changes with regard to IAVL, stores, and pruning settings.**
 * (x/distribution) [\#6210](https://github.com/cosmos/cosmos-sdk/pull/6210) Register `MsgFundCommunityPool` in distribution amino codec.
 * (types) [\#5741](https://github.com/cosmos/cosmos-sdk/issues/5741) Prevent `ChainAnteDecorators()` from panicking when empty `AnteDecorator` slice is supplied.
+* (baseapp) [\#6306](https://github.com/cosmos/cosmos-sdk/issues/6306) Prevent events emitted by the antehandler from being persisted between transactions.
 
 ## [v0.38.4] - 2020-05-21
 

baseapp/baseapp.go

@@ -604,8 +604,9 @@ func (app *BaseApp) runTx(mode runTxMode, txBytes []byte, tx sdk.Tx) (gInfo sdk.
 		// writes do not happen if aborted/failed.  This may have some
 		// performance benefits, but it'll be more difficult to get right.
 		anteCtx, msCache = app.cacheTxContext(ctx, txBytes)
-
+		anteCtx = anteCtx.WithEventManager(sdk.NewEventManager())
 		newCtx, err := app.anteHandler(anteCtx, tx, mode == runTxModeSimulate)
+
 		if !newCtx.IsZero() {
 			// At this point, newCtx.MultiStore() is cache-wrapped, or something else
 			// replaced by the AnteHandler. We want the original multistore, not one

baseapp/baseapp_test.go

@@ -658,20 +658,33 @@ func testTxDecoder(cdc *codec.Codec) sdk.TxDecoder {
 }
 
 func anteHandlerTxTest(t *testing.T, capKey sdk.StoreKey, storeKey []byte) sdk.AnteHandler {
-	return func(ctx sdk.Context, tx sdk.Tx, simulate bool) (newCtx sdk.Context, err error) {
+	return func(ctx sdk.Context, tx sdk.Tx, simulate bool) (sdk.Context, error) {
 		store := ctx.KVStore(capKey)
 		txTest := tx.(txTest)
 
 		if txTest.FailOnAnte {
-			return newCtx, sdkerrors.Wrap(sdkerrors.ErrUnauthorized, "ante handler failure")
+			return ctx, sdkerrors.Wrap(sdkerrors.ErrUnauthorized, "ante handler failure")
 		}
 
-		_, err = incrementingCounter(t, store, storeKey, txTest.Counter)
+		_, err := incrementingCounter(t, store, storeKey, txTest.Counter)
 		if err != nil {
-			return newCtx, err
+			return ctx, err
 		}
 
-		return newCtx, nil
+		ctx.EventManager().EmitEvents(
+			counterEvent("ante_handler", txTest.Counter),
+		)
+
+		return ctx, nil
+	}
+}
+
+func counterEvent(evType string, msgCount int64) sdk.Events {
+	return sdk.Events{
+		sdk.NewEvent(
+			evType,
+			sdk.NewAttribute("update_counter", fmt.Sprintf("%d", msgCount)),
+		),
 	}
 }
 
@@ -1288,6 +1301,7 @@ func TestBaseAppAnteHandler(t *testing.T) {
 	txBytes, err := cdc.MarshalBinaryLengthPrefixed(tx)
 	require.NoError(t, err)
 	res := app.DeliverTx(abci.RequestDeliverTx{Tx: txBytes})
+	require.Empty(t, res.Events)
 	require.False(t, res.IsOK(), fmt.Sprintf("%v", res))
 
 	ctx := app.getState(runTxModeDeliver).ctx
@@ -1303,6 +1317,7 @@ func TestBaseAppAnteHandler(t *testing.T) {
 	require.NoError(t, err)
 
 	res = app.DeliverTx(abci.RequestDeliverTx{Tx: txBytes})
+	require.Empty(t, res.Events)
 	require.False(t, res.IsOK(), fmt.Sprintf("%v", res))
 
 	ctx = app.getState(runTxModeDeliver).ctx
@@ -1318,6 +1333,7 @@ func TestBaseAppAnteHandler(t *testing.T) {
 	require.NoError(t, err)
 
 	res = app.DeliverTx(abci.RequestDeliverTx{Tx: txBytes})
+	require.NotEmpty(t, res.Events)
 	require.True(t, res.IsOK(), fmt.Sprintf("%v", res))
 
 	ctx = app.getState(runTxModeDeliver).ctx