Fix:(issue_1755) Ensure that timestamp flag destination is set correctly

flag_test.go

@@ -3459,6 +3459,28 @@ func TestTimestampFlagApply_WithDestination(t *testing.T) {
 	expect(t, *fl.Destination.timestamp, expectedResult)
 }
 
+func TestTimestampFlagApply_EnvWithDestination(t *testing.T) {
+	var tsValue Timestamp
+
+	app := NewApp()
+	app.Flags = []Flag{
+		&TimestampFlag{
+			Name:        "some-timestamp-flag",
+			EnvVars:     []string{"SOME_TIMESTAMP_FLAG"},
+			Layout:      time.RFC3339,
+			Destination: &tsValue,
+			Required:    true,
+		},
+	}
+
+	t.Setenv("SOME_TIMESTAMP_FLAG", "2021-03-02T06:20:00Z")
+
+	err := app.Run([]string{})
+
+	expect(t, err, nil)
+	expect(t, tsValue.Value().Format(time.RFC3339), "2021-03-02T06:20:00Z")
+}
+
 // Test issue #1254
 // StringSlice() with UseShortOptionHandling causes duplicated entries, depending on the ordering of the flags
 func TestSliceShortOptionHandle(t *testing.T) {

flag_timestamp.go

@@ -145,18 +145,17 @@ func (f *TimestampFlag) Apply(set *flag.FlagSet) error {
 
 	f.defaultValue = f.Value.clone()
 
-	if f.Destination != nil {
-		f.Destination.SetLayout(f.Layout)
-		f.Destination.SetLocation(f.Timezone)
-	}
-
 	if val, source, found := flagFromEnvOrFile(f.EnvVars, f.FilePath); found {
 		if err := f.Value.Set(val); err != nil {
 			return fmt.Errorf("could not parse %q as timestamp value from %s for flag %s: %s", val, source, f.Name, err)
 		}
 		f.HasBeenSet = true
 	}
 
+	if f.Destination != nil {
+		*f.Destination = *f.Value
+	}
+
 	for _, name := range f.Names() {
 		if f.Destination != nil {
 			set.Var(f.Destination, name, f.Usage)