feat: add support of null to remove the CORS configuration from bucket

google-cloud-storage/src/main/java/com/google/cloud/storage/BucketInfo.java

@@ -1240,7 +1240,7 @@ Builder setMetageneration(Long metageneration) {
 
     @Override
     public Builder setCors(Iterable<Cors> cors) {
-      this.cors = cors != null ? ImmutableList.copyOf(cors) : null;
+      this.cors = cors != null ? ImmutableList.copyOf(cors) : ImmutableList.<Cors>of();
       return this;
     }
 

google-cloud-storage/src/test/java/com/google/cloud/storage/BucketTest.java

@@ -886,4 +886,36 @@ public void testUpdateBucketLogging() {
     assertThat(actualUpdatedBucket.getLogging().getLogBucket()).isNull();
     assertThat(actualUpdatedBucket.getLogging().getLogObjectPrefix()).isNull();
   }
+
+  @Test
+  public void testRemoveBucketCORS() {
+    initializeExpectedBucket(6);
+    List<Cors.Origin> origins = ImmutableList.of(Cors.Origin.of("http://cloud.google.com"));
+    List<HttpMethod> httpMethods = ImmutableList.of(HttpMethod.GET);
+    List<String> responseHeaders = ImmutableList.of("Content-Type");
+    Cors cors =
+        Cors.newBuilder()
+            .setOrigins(origins)
+            .setMethods(httpMethods)
+            .setResponseHeaders(responseHeaders)
+            .setMaxAgeSeconds(100)
+            .build();
+    BucketInfo bucketInfo = BucketInfo.newBuilder("b").setCors(ImmutableList.of(cors)).build();
+    Bucket bucket = new Bucket(serviceMockReturnsOptions, new BucketInfo.BuilderImpl(bucketInfo));
+    assertThat(bucket.getCors()).isNotNull();
+    assertThat(bucket.getCors().get(0).getMaxAgeSeconds()).isEqualTo(100);
+    assertThat(bucket.getCors().get(0).getMethods()).isEqualTo(httpMethods);
+    assertThat(bucket.getCors().get(0).getOrigins()).isEqualTo(origins);
+    assertThat(bucket.getCors().get(0).getResponseHeaders()).isEqualTo(responseHeaders);
+
+    // Remove bucket CORS configuration.
+    Bucket expectedUpdatedBucket = bucket.toBuilder().setCors(null).build();
+    expect(storage.getOptions()).andReturn(mockOptions).times(2);
+    expect(storage.update(expectedUpdatedBucket)).andReturn(expectedUpdatedBucket);
+    replay(storage);
+    initializeBucket();
+    Bucket updatedBucket = new Bucket(storage, new BucketInfo.BuilderImpl(expectedUpdatedBucket));
+    Bucket actualUpdatedBucket = updatedBucket.update();
+    assertThat(actualUpdatedBucket.getCors()).isEmpty();
+  }
 }

google-cloud-storage/src/test/java/com/google/cloud/storage/it/ITStorageTest.java

@@ -66,6 +66,7 @@
 import com.google.cloud.storage.BucketInfo.LifecycleRule.LifecycleAction;
 import com.google.cloud.storage.BucketInfo.LifecycleRule.LifecycleCondition;
 import com.google.cloud.storage.CopyWriter;
+import com.google.cloud.storage.Cors;
 import com.google.cloud.storage.HmacKey;
 import com.google.cloud.storage.HttpMethod;
 import com.google.cloud.storage.PostPolicyV4;
@@ -3474,4 +3475,50 @@ public void testAutoContentTypeCreateFrom() throws IOException {
   public void testAutoContentTypeWriter() throws IOException {
     testAutoContentType("writer");
   }
+
+  @Test
+  public void testRemoveBucketCORS() throws ExecutionException, InterruptedException {
+    String bucketName = RemoteStorageHelper.generateBucketName();
+    List<Cors.Origin> origins = ImmutableList.of(Cors.Origin.of("http://cloud.google.com"));
+    List<HttpMethod> httpMethods = ImmutableList.of(HttpMethod.GET);
+    List<String> responseHeaders = ImmutableList.of("Content-Type");
+    try {
+      Cors cors =
+          Cors.newBuilder()
+              .setOrigins(origins)
+              .setMethods(httpMethods)
+              .setResponseHeaders(responseHeaders)
+              .setMaxAgeSeconds(100)
+              .build();
+      storage.create(BucketInfo.newBuilder(bucketName).setCors(ImmutableList.of(cors)).build());
+
+      // case-1 : Cors are set and field selector is selected then returns not-null.
+      Bucket remoteBucket =
+          storage.get(bucketName, Storage.BucketGetOption.fields(BucketField.CORS));
+      assertThat(remoteBucket.getCors()).isNotNull();
+      assertThat(remoteBucket.getCors().get(0).getMaxAgeSeconds()).isEqualTo(100);
+      assertThat(remoteBucket.getCors().get(0).getMethods()).isEqualTo(httpMethods);
+      assertThat(remoteBucket.getCors().get(0).getOrigins()).isEqualTo(origins);
+      assertThat(remoteBucket.getCors().get(0).getResponseHeaders()).isEqualTo(responseHeaders);
+
+      // case-2 : Cors are set but field selector isn't selected then returns not-null.
+      remoteBucket = storage.get(bucketName);
+      assertThat(remoteBucket.getCors()).isNotNull();
+
+      // Remove CORS configuration from the bucket.
+      Bucket updatedBucket = remoteBucket.toBuilder().setCors(null).build().update();
+      assertThat(updatedBucket.getCors()).isNull();
+
+      // case-3 : Cors are not set and field selector is selected then returns null.
+      updatedBucket = storage.get(bucketName, Storage.BucketGetOption.fields(BucketField.CORS));
+      assertThat(updatedBucket.getCors()).isNull();
+
+      // case-4 : Cors are not set and field selector isn't selected then returns null.
+      updatedBucket = storage.get(bucketName);
+      assertThat(updatedBucket.getCors()).isNull();
+
+    } finally {
+      RemoteStorageHelper.forceDelete(storage, bucketName, 5, TimeUnit.SECONDS);
+    }
+  }
 }