From b453a17d8809bf884fe9e07ce9800ea3933ab2cc Mon Sep 17 00:00:00 2001
From: "vitess-bot[bot]" <108069721+vitess-bot[bot]@users.noreply.github.com>
Date: Mon, 20 Jan 2025 12:21:08 +0100
Subject: [PATCH] [release-19.0] Always return a valid timezone in cursor
 (#17546) (#17549)

---
 go/vt/vtgate/engine/fake_vcursor_test.go |  2 +-
 go/vt/vtgate/evalengine/fn_time.go       |  4 ++--
 go/vt/vtgate/safe_session.go             |  9 ++++++---
 go/vt/vtgate/safe_session_test.go        | 14 ++++++++++----
 4 files changed, 19 insertions(+), 10 deletions(-)

diff --git a/go/vt/vtgate/engine/fake_vcursor_test.go b/go/vt/vtgate/engine/fake_vcursor_test.go
index 08a40c0d835..330cd725920 100644
--- a/go/vt/vtgate/engine/fake_vcursor_test.go
+++ b/go/vt/vtgate/engine/fake_vcursor_test.go
@@ -140,7 +140,7 @@ func (t *noopVCursor) Environment() *vtenv.Environment {
 }
 
 func (t *noopVCursor) TimeZone() *time.Location {
-	return nil
+	return time.Local
 }
 
 func (t *noopVCursor) SQLMode() string {
diff --git a/go/vt/vtgate/evalengine/fn_time.go b/go/vt/vtgate/evalengine/fn_time.go
index 8245de7669f..f01d7c7f9bb 100644
--- a/go/vt/vtgate/evalengine/fn_time.go
+++ b/go/vt/vtgate/evalengine/fn_time.go
@@ -232,7 +232,7 @@ func (call *builtinNow) constant() bool {
 
 func (call *builtinSysdate) eval(env *ExpressionEnv) (eval, error) {
 	now := SystemTime()
-	if tz := env.currentTimezone(); tz != nil {
+	if tz := env.currentTimezone(); tz != time.Local {
 		now = now.In(tz)
 	}
 	return newEvalDateTime(datetime.NewDateTimeFromStd(now), int(call.prec), false), nil
@@ -673,7 +673,7 @@ func (b *builtinFromUnixtime) eval(env *ExpressionEnv) (eval, error) {
 	}
 
 	t := time.Unix(sec, frac)
-	if tz := env.currentTimezone(); tz != nil {
+	if tz := env.currentTimezone(); tz != time.Local {
 		t = t.In(tz)
 	}
 
diff --git a/go/vt/vtgate/safe_session.go b/go/vt/vtgate/safe_session.go
index 45fff46f629..54aa3f752de 100644
--- a/go/vt/vtgate/safe_session.go
+++ b/go/vt/vtgate/safe_session.go
@@ -26,7 +26,6 @@ import (
 	"google.golang.org/protobuf/proto"
 
 	"vitess.io/vitess/go/mysql/datetime"
-
 	"vitess.io/vitess/go/vt/sqlparser"
 	"vitess.io/vitess/go/vt/srvtopo"
 	"vitess.io/vitess/go/vt/sysvars"
@@ -567,9 +566,13 @@ func (session *SafeSession) TimeZone() *time.Location {
 	session.mu.Unlock()
 
 	if !ok {
-		return nil
+		return time.Local
+	}
+
+	loc, err := datetime.ParseTimeZone(tz)
+	if err != nil {
+		return time.Local
 	}
-	loc, _ := datetime.ParseTimeZone(tz)
 	return loc
 }
 
diff --git a/go/vt/vtgate/safe_session_test.go b/go/vt/vtgate/safe_session_test.go
index 21bb2d6697a..199b9239bf2 100644
--- a/go/vt/vtgate/safe_session_test.go
+++ b/go/vt/vtgate/safe_session_test.go
@@ -72,6 +72,10 @@ func TestTimeZone(t *testing.T) {
 		tz   string
 		want string
 	}{
+		{
+			tz:   "",
+			want: time.Local.String(),
+		},
 		{
 			tz:   "Europe/Amsterdam",
 			want: "Europe/Amsterdam",
@@ -82,16 +86,18 @@ func TestTimeZone(t *testing.T) {
 		},
 		{
 			tz:   "foo",
-			want: (*time.Location)(nil).String(),
+			want: time.Local.String(),
 		},
 	}
 
 	for _, tc := range testCases {
 		t.Run(tc.tz, func(t *testing.T) {
+			sysvars := map[string]string{}
+			if tc.tz != "" {
+				sysvars["time_zone"] = tc.tz
+			}
 			session := NewSafeSession(&vtgatepb.Session{
-				SystemVariables: map[string]string{
-					"time_zone": tc.tz,
-				},
+				SystemVariables: sysvars,
 			})
 
 			assert.Equal(t, tc.want, session.TimeZone().String())