fix: Allow Pub/Sub Topic update to remove schema settings (#11038)

mmv1/products/pubsub/Topic.yaml

@@ -124,7 +124,6 @@ properties:
     name: 'schemaSettings'
     description: |
       Settings for validating messages published against a schema.
-    default_from_api: true
     properties:
       - !ruby/object:Api::Type::String
         name: 'schema'

mmv1/third_party/terraform/services/pubsub/resource_pubsub_topic_test.go

@@ -93,6 +93,9 @@ func TestAccPubsubTopic_schema(t *testing.T) {
 			{
 				Config: testAccPubsubTopic_updateWithNewSchema(topic, schema2),
 			},
+			{
+				Config: testAccPubsubTopic_updateWithNewSchema(topic, ""),
+			},
 			{
 				ResourceName:      "google_pubsub_topic.bar",
 				ImportStateId:     topic,
@@ -228,7 +231,8 @@ resource "google_pubsub_topic" "bar" {
 }
 
 func testAccPubsubTopic_updateWithNewSchema(topic, schema string) string {
-	return fmt.Sprintf(`
+	if schema != "" {
+		return fmt.Sprintf(`
 resource "google_pubsub_schema" "foo" {
 	name = "%s"
 	type = "PROTOCOL_BUFFER"
@@ -243,6 +247,13 @@ resource "google_pubsub_topic" "bar" {
   }
 }
 `, schema, topic)
+	} else {
+		return fmt.Sprintf(`
+		resource "google_pubsub_topic" "bar" {
+			name = "%s"
+		}
+		`, topic)
+	}
 }
 
 func testAccPubsubTopic_updateWithKinesisIngestionSettings(topic string) string {

mmv1/third_party/terraform/website/docs/guides/version_6_upgrade.html.markdown

@@ -113,3 +113,9 @@ Description of the change and how users should adjust their configuration (if ne
 ### `settings.ip_configuration.require_ssl` is now removed
 
 Removed in favor of field `settings.ip_configuration.ssl_mode`.
+
+## Resource: `google_pubsub_topic`
+
+### `schema_settings` no longer has a default value
+
+An empty value means the setting should be cleared.