cloud_tasks_queue: supress permadiffs on backoff settings (#8359)

Add `tpgresource.DurationDiffSuppress` to min / max backoff
Fixes https://github.com/hashicorp/terraform-provider-google/issues/15166x

mmv1/products/cloudtasks/Queue.yaml

@@ -172,13 +172,15 @@ properties:
           maxBackoff duration after it fails, if the queue's RetryConfig
           specifies that the task should be retried.
         default_from_api: true
+        diff_suppress_func: 'tpgresource.DurationDiffSuppress'
       - !ruby/object:Api::Type::String
         name: 'maxBackoff'
         description: |
           A task will be scheduled for retry between minBackoff and
           maxBackoff duration after it fails, if the queue's RetryConfig
           specifies that the task should be retried.
         default_from_api: true
+        diff_suppress_func: 'tpgresource.DurationDiffSuppress'
       - !ruby/object:Api::Type::Integer
         name: 'maxDoublings'
         description: |

mmv1/templates/terraform/constants/cloud_tasks_retry_config_custom_diff.go

@@ -1,7 +1,7 @@
-func suppressOmittedMaxDuration(_, old, new string, _ *schema.ResourceData) bool {
+func suppressOmittedMaxDuration(k, old, new string, d *schema.ResourceData) bool {
 	if old == "" && new == "0s" {
 		log.Printf("[INFO] max retry is 0s and api omitted field, suppressing diff")
 		return true
 	}
-	return false
+	return tpgresource.DurationDiffSuppress(k, old, new, d)
 }

mmv1/third_party/terraform/tests/resource_cloud_tasks_queue_test.go.erb

@@ -91,6 +91,29 @@ func TestAccCloudTasksQueue_MaxRetryDiffSuppress0s(t *testing.T) {
 	})
 }
 
+// Make sure the diff suppression function handles the situation where an
+// unexpected time unit is used, e.g., 2.0s instead of 2s or 2.0s instead of
+// 2.000s
+func TestAccCloudTasksQueue_TimeUnitDiff(t *testing.T) {
+	t.Parallel()
+	testID := acctest.RandString(t, 10)
+	cloudTaskName := fmt.Sprintf("tf-test-%s", testID)
+	acctest.VcrTest(t, resource.TestCase{
+		PreCheck:                 func() { acctest.AccTestPreCheck(t) },
+		ProtoV5ProviderFactories: acctest.ProtoV5ProviderFactories(t),
+		Steps: []resource.TestStep{
+			{
+				Config: testAccCloudtasksQueueTimeUnitDiff(cloudTaskName),
+			},
+			{
+				ResourceName:      "google_cloud_tasks_queue.default",
+				ImportState:       true,
+				ImportStateVerify: true,
+			},
+		},
+	})
+}
+
 func testAccCloudTasksQueue_basic(name string) string {
 	return fmt.Sprintf(`
 resource "google_cloud_tasks_queue" "default" {
@@ -185,3 +208,20 @@ func testAccCloudtasksQueueMaxRetry0s(cloudTaskName string) string {
 	}
 `, cloudTaskName)
 }
+
+func testAccCloudtasksQueueTimeUnitDiff(cloudTaskName string) string {
+	return fmt.Sprintf(`
+resource "google_cloud_tasks_queue" "default" {
+  name     = "%s"
+  location = "us-central1"
+
+  retry_config {
+    max_attempts       = -1
+    max_backoff        = "5.000s"
+    max_doublings      = 16
+    max_retry_duration = "1.0s"
+    min_backoff        = "0.10s"
+  }
+}
+`, cloudTaskName)
+}