Add identity for deleted topics

gcloud-java-pubsub/src/main/java/com/google/cloud/pubsub/SubscriptionInfo.java

@@ -182,6 +182,8 @@ public SubscriptionInfo build() {
   /**
    * Returns the identity of the topic this subscription refers to. If {@link TopicId#project()} is
    * {@code null} the topic is assumed to reside in the {@link PubSubOptions#projectId()} project.
+   * After a topic is deleted, existing subscriptions to that topic are not deleted, but their topic
+   * field is set to {@link TopicId#deletedTopic()}.
    */
   public TopicId topic() {
     return topic;

gcloud-java-pubsub/src/main/java/com/google/cloud/pubsub/TopicId.java

@@ -33,13 +33,21 @@
 public final class TopicId implements Serializable {
 
   private static final long serialVersionUID = -4913169763174877777L;
+  private static final String DELETED_TOPIC_NAME = "_deleted_topic_";
+  private static final TopicId DELETED_TOPIC = new TopicId(null, DELETED_TOPIC_NAME, true);
 
   private final String project;
   private final String topic;
+  private final boolean isDeleted;
 
-  private TopicId(String project, String topic) {
+  private TopicId(String project, String topic, boolean isDeleted) {
     this.project = project;
     this.topic = checkNotNull(topic);
+    this.isDeleted = isDeleted;
+  }
+
+  private TopicId(String project, String topic) {
+    this(project, topic, false);
   }
 
   /**
@@ -57,14 +65,27 @@ public String topic() {
     return topic;
   }
 
+  /**
+   * Returns {@code true} if this object is the identity of a deleted topic, {@code false}
+   * otherwhise. If {@code isDeleted()} is {@code true}, {@link #topic()} returns
+   * "{@code _deleted_topic_}" and {@link #project()} returns {@code null}.
+   */
+  public boolean isDeleted() {
+    return isDeleted;
+  }
+
   @Override
   public String toString() {
-    return MoreObjects.toStringHelper(this).add("project", project).add("topic", topic).toString();
+    return MoreObjects.toStringHelper(this)
+        .add("project", project)
+        .add("topic", topic)
+        .add("isDeleted", isDeleted)
+        .toString();
   }
 
   @Override
   public int hashCode() {
-    return Objects.hash(project, topic);
+    return Objects.hash(project, topic, isDeleted);
   }
 
   @Override
@@ -76,13 +97,24 @@ public boolean equals(Object obj) {
       return false;
     }
     TopicId other = (TopicId) obj;
-    return Objects.equals(project, other.project) && Objects.equals(topic, other.topic);
+    return Objects.equals(project, other.project)
+        && Objects.equals(topic, other.topic)
+        && Objects.equals(isDeleted, other.isDeleted);
   }
 
   String toPb(String projectId) {
     return formatTopicName(project != null ? project : projectId, topic);
   }
 
+  /**
+   * Returns the identity of a deleted topic. The deleted topic is such that {@link #isDeleted()}
+   * returns {@code true}, {@link #topic()} returns "{@code _is_deleted_}" and {@link #project()}
+   * returns {@code null}.
+   */
+  public static TopicId deletedTopic() {
+    return DELETED_TOPIC;
+  }
+
   /**
    * Returns a topic identity given the topic name.
    */
@@ -98,6 +130,9 @@ public static TopicId of(String project, String topic) {
   }
 
   static TopicId fromPb(String pb) {
+    if (Objects.equals(pb, DELETED_TOPIC_NAME)) {
+      return DELETED_TOPIC;
+    }
     return TopicId.of(parseProjectFromTopicName(pb), parseTopicFromTopicName(pb));
   }
 }

gcloud-java-pubsub/src/test/java/com/google/cloud/pubsub/SubscriptionIdTest.java

@@ -43,8 +43,8 @@ public void testToAndFromPb() {
 
   private void compareSubscriptionId(SubscriptionId expected, SubscriptionId value) {
     assertEquals(expected, value);
-    assertEquals(expected.project(), expected.project());
-    assertEquals(expected.subscription(), expected.subscription());
-    assertEquals(expected.hashCode(), expected.hashCode());
+    assertEquals(expected.project(), value.project());
+    assertEquals(expected.subscription(), value.subscription());
+    assertEquals(expected.hashCode(), value.hashCode());
   }
 }

gcloud-java-pubsub/src/test/java/com/google/cloud/pubsub/SubscriptionInfoTest.java

@@ -111,6 +111,13 @@ public void testToAndFromPb() {
     subscriptionInfo = SubscriptionInfo.of("topic", NAME, ENDPOINT);
     compareSubscriptionInfo(SubscriptionInfo.of(TOPIC, NAME, ENDPOINT),
         SubscriptionInfo.fromPb(subscriptionInfo.toPb("project")));
+    com.google.pubsub.v1.Subscription subscription = SUBSCRIPTION_INFO.toPb("project");
+    subscriptionInfo =
+        SubscriptionInfo.fromPb(subscription.toBuilder().setTopic("_deleted_topic_").build());
+    assertEquals(TopicId.deletedTopic(), subscriptionInfo.topic());
+    assertEquals(NAME, subscriptionInfo.name());
+    assertEquals(PUSH_CONFIG, subscriptionInfo.pushConfig());
+    assertEquals(ACK_DEADLINE, subscriptionInfo.ackDeadlineSeconds());
   }
 
   private void compareSubscriptionInfo(SubscriptionInfo expected, SubscriptionInfo value) {

gcloud-java-pubsub/src/test/java/com/google/cloud/pubsub/TopicIdTest.java

@@ -17,7 +17,10 @@
 package com.google.cloud.pubsub;
 
 import static org.junit.Assert.assertEquals;
+import static org.junit.Assert.assertFalse;
 import static org.junit.Assert.assertNull;
+import static org.junit.Assert.assertSame;
+import static org.junit.Assert.assertTrue;
 
 import org.junit.Test;
 
@@ -35,6 +38,16 @@ public void testOf() {
     topicId = TopicId.of(NAME);
     assertNull(topicId.project());
     assertEquals(NAME, topicId.topic());
+    assertFalse(topicId.isDeleted());
+  }
+
+  @Test
+  public void testDeletedTopic() {
+    TopicId deletedTopic = TopicId.deletedTopic();
+    assertNull(deletedTopic.project());
+    assertEquals("_deleted_topic_", deletedTopic.topic());
+    assertTrue(deletedTopic.isDeleted());
+    assertSame(deletedTopic, TopicId.deletedTopic());
   }
 
   @Test
@@ -51,9 +64,10 @@ public void testToAndFromPb() {
 
   private void compareTopicId(TopicId expected, TopicId value) {
     assertEquals(expected, value);
-    assertEquals(expected.project(), expected.project());
-    assertEquals(expected.topic(), expected.topic());
-    assertEquals(expected.toPb("project"), expected.toPb("project"));
-    assertEquals(expected.hashCode(), expected.hashCode());
+    assertEquals(expected.project(), value.project());
+    assertEquals(expected.topic(), value.topic());
+    assertEquals(expected.isDeleted(), value.isDeleted());
+    assertEquals(expected.toPb("project"), value.toPb("project"));
+    assertEquals(expected.hashCode(), value.hashCode());
   }
 }