Add ability to remove "Parent" transactions from the mempool (#582)

* add the new transaction wrapper

* export and move DecodeChildTx

* return a more precise type (Tx instead of []byte) for DecodeChildTx

* add test and helper function

* linter

buf.yaml

@@ -1,3 +1,5 @@
+version: v1beta1
+
 build:
   roots:
     - proto

mempool/clist_mempool.go

@@ -605,6 +605,12 @@ func (mem *CListMempool) Update(
 		// https://github.com/tendermint/tendermint/issues/3322.
 		if e, ok := mem.txsMap.Load(TxKey(tx)); ok {
 			mem.removeTx(tx, e.(*clist.CElement), false)
+			// see if the transaction is a child transaction of a some parent
+			// transaction that exists in the mempool
+		} else if parentHash, _, isChild := types.DecodeChildTx(tx); isChild {
+			var parentKey [TxKeySize]byte
+			copy(parentKey[:], parentHash)
+			mem.RemoveTxByKey(parentKey, false)
 		}
 	}
 

mempool/clist_mempool_test.go

@@ -214,6 +214,29 @@ func TestMempoolUpdate(t *testing.T) {
 		err = mempool.CheckTx([]byte{0x03}, nil, TxInfo{})
 		require.NoError(t, err)
 	}
+
+	// 4. Removes a parent transaction after receiving a child transaction in the update
+	{
+		mempool.Flush()
+		parentTx := []byte{1, 2, 3, 4}
+		childTx := []byte{1, 2}
+		parentHash := sha256.Sum256(parentTx)
+
+		// create the wrapped child transaction
+		wTx, err := types.WrapChildTx(parentHash[:], childTx)
+		require.NoError(t, err)
+
+		// add the parent transaction to the mempool
+		err = mempool.CheckTx(parentTx, nil, TxInfo{})
+		require.NoError(t, err)
+
+		// remove the parent from the mempool using the wrapped child tx
+		err = mempool.Update(1, []types.Tx{wTx}, abciResponses(1, abci.CodeTypeOK), nil, nil)
+		require.NoError(t, err)
+
+		assert.Zero(t, mempool.Size())
+
+	}
 }
 
 func TestMempool_KeepInvalidTxsInCache(t *testing.T) {