mark field as updatable (#4371) (#2942)

Co-authored-by: upodroid <[email protected]>
Signed-off-by: Modular Magician <[email protected]>

Co-authored-by: upodroid <[email protected]>

Author: modular-magician

.changelog/4371.txt

@@ -0,0 +1,3 @@
+```release-note:enhancement
+pubsub: marked `kms_key_name` field in `google_pubsub_topic` as updatable
+```

google-beta/resource_pubsub_topic.go

@@ -52,7 +52,6 @@ func resourcePubsubTopic() *schema.Resource {
 			"kms_key_name": {
 				Type:     schema.TypeString,
 				Optional: true,
-				ForceNew: true,
 				Description: `The resource name of the Cloud KMS CryptoKey to be used to protect access
 to messages published on this topic. Your project's PubSub service account
 ('service-{{PROJECT_NUMBER}}@gcp-sa-pubsub.iam.gserviceaccount.com') must have
@@ -282,6 +281,12 @@ func resourcePubsubTopicUpdate(d *schema.ResourceData, meta interface{}) error {
 	billingProject = project
 
 	obj := make(map[string]interface{})
+	kmsKeyNameProp, err := expandPubsubTopicKmsKeyName(d.Get("kms_key_name"), d, config)
+	if err != nil {
+		return err
+	} else if v, ok := d.GetOkExists("kms_key_name"); !isEmptyValue(reflect.ValueOf(v)) && (ok || !reflect.DeepEqual(v, kmsKeyNameProp)) {
+		obj["kmsKeyName"] = kmsKeyNameProp
+	}
 	labelsProp, err := expandPubsubTopicLabels(d.Get("labels"), d, config)
 	if err != nil {
 		return err
@@ -308,6 +313,10 @@ func resourcePubsubTopicUpdate(d *schema.ResourceData, meta interface{}) error {
 	log.Printf("[DEBUG] Updating Topic %q: %#v", d.Id(), obj)
 	updateMask := []string{}
 
+	if d.HasChange("kms_key_name") {
+		updateMask = append(updateMask, "kmsKeyName")
+	}
+
 	if d.HasChange("labels") {
 		updateMask = append(updateMask, "labels")
 	}