Relax diff on maintenance_policy.daily_maintenance_window.start_time (#726)

* Relax diff on maintenance_policy.daily_maintenance_window.start_time

If the maintenance window has been set outside of Terraform to a time with a
single-digit hour (such as 1:00), and the terraform definition is set to the
same hour but with a leading zero as per validation (i.e. 01:00), do not
consider the time to be changed (as we currently don't support update on this
property).

Fixes #719

* Generalise rfc3339TimeDiffSuppress and add more test cases

google/resource_container_cluster.go

@@ -187,10 +187,11 @@ func resourceContainerCluster() *schema.Resource {
 							Elem: &schema.Resource{
 								Schema: map[string]*schema.Schema{
 									"start_time": {
-										Type:         schema.TypeString,
-										Required:     true,
-										ForceNew:     true,
-										ValidateFunc: validateRFC3339Time,
+										Type:             schema.TypeString,
+										Required:         true,
+										ForceNew:         true,
+										ValidateFunc:     validateRFC3339Time,
+										DiffSuppressFunc: rfc3339TimeDiffSuppress,
 									},
 									"duration": {
 										Type:     schema.TypeString,

google/utils.go

@@ -293,6 +293,15 @@ func portRangeDiffSuppress(k, old, new string, d *schema.ResourceData) bool {
 	return false
 }
 
+// Single-digit hour is equivalent to hour with leading zero e.g. suppress diff 1:00 => 01:00.
+// Assume either value could be in either format.
+func rfc3339TimeDiffSuppress(k, old, new string, d *schema.ResourceData) bool {
+	if (len(old) == 4 && "0"+old == new) || (len(new) == 4 && "0"+new == old) {
+		return true
+	}
+	return false
+}
+
 // expandLabels pulls the value of "labels" out of a schema.ResourceData as a map[string]string.
 func expandLabels(d *schema.ResourceData) map[string]string {
 	return expandStringMap(d, "labels")

google/utils_test.go

@@ -93,3 +93,46 @@ func TestIpCidrRangeDiffSuppress(t *testing.T) {
 		}
 	}
 }
+
+func TestRfc3339TimeDiffSuppress(t *testing.T) {
+	cases := map[string]struct {
+		Old, New          string
+		ExpectDiffSupress bool
+	}{
+		"same time, format changed to have leading zero": {
+			Old:               "2:00",
+			New:               "02:00",
+			ExpectDiffSupress: true,
+		},
+		"same time, format changed not to have leading zero": {
+			Old:               "02:00",
+			New:               "2:00",
+			ExpectDiffSupress: true,
+		},
+		"different time, both without leading zero": {
+			Old:               "2:00",
+			New:               "3:00",
+			ExpectDiffSupress: false,
+		},
+		"different time, old with leading zero, new without": {
+			Old:               "02:00",
+			New:               "3:00",
+			ExpectDiffSupress: false,
+		},
+		"different time, new with leading zero, oldwithout": {
+			Old:               "2:00",
+			New:               "03:00",
+			ExpectDiffSupress: false,
+		},
+		"different time, both with leading zero": {
+			Old:               "02:00",
+			New:               "03:00",
+			ExpectDiffSupress: false,
+		},
+	}
+	for tn, tc := range cases {
+		if rfc3339TimeDiffSuppress("time", tc.Old, tc.New, nil) != tc.ExpectDiffSupress {
+			t.Errorf("bad: %s, '%s' => '%s' expect DiffSuppress to return %t", tn, tc.Old, tc.New, tc.ExpectDiffSupress)
+		}
+	}
+}