database/sql: de-flake TestTxCannotCommitAfterRollback

Do not cancel rows during test. Only cancel the Tx.
Correct the referenced issue number on the test.

Fixes #38597

Change-Id: I0e8ba1bf2a8ba638d121c9c6938501fec1d5e961
Reviewed-on: https://go-review.googlesource.com/c/go/+/229478
Run-TryBot: Daniel Theophanes <kardianos@gmail.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/database/sql/sql.go

@@ -2793,10 +2793,17 @@ func (rs *Rows) lasterrOrErrLocked(err error) error {
 	return err
 }
 
+// bypassRowsAwaitDone is only used for testing.
+// If true, it will not close the Rows automatically from the context.
+var bypassRowsAwaitDone = false
+
 func (rs *Rows) initContextClose(ctx, txctx context.Context) {
 	if ctx.Done() == nil && (txctx == nil || txctx.Done() == nil) {
 		return
 	}
+	if bypassRowsAwaitDone {
+		return
+	}
 	ctx, rs.cancel = context.WithCancel(ctx)
 	go rs.awaitDone(ctx, txctx)
 }

src/database/sql/sql_test.go

@@ -2742,7 +2742,7 @@ func TestManyErrBadConn(t *testing.T) {
 	}
 }
 
-// Issue 34755: Ensure that a Tx cannot commit after a rollback.
+// Issue 34775: Ensure that a Tx cannot commit after a rollback.
 func TestTxCannotCommitAfterRollback(t *testing.T) {
 	db := newTestDB(t, "tx_status")
 	defer closeDB(t, db)
@@ -2784,6 +2784,9 @@ func TestTxCannotCommitAfterRollback(t *testing.T) {
 	// 2. (A) Start a query, (B) begin Tx rollback through a ctx cancel.
 	// 3. Check if 2.A has committed in Tx (pass) or outside of Tx (fail).
 	sendQuery := make(chan struct{})
+	// The Tx status is returned through the row results, ensure
+	// that the rows results are not cancelled.
+	bypassRowsAwaitDone = true
 	hookTxGrabConn = func() {
 		cancel()
 		<-sendQuery
@@ -2794,6 +2797,7 @@ func TestTxCannotCommitAfterRollback(t *testing.T) {
 	defer func() {
 		hookTxGrabConn = nil
 		rollbackHook = nil
+		bypassRowsAwaitDone = false
 	}()
 
 	err = tx.QueryRow("SELECT|tx_status|tx_status|").Scan(&txStatus)