Add NoAuthCredentials

gcloud-java-core/src/main/java/com/google/gcloud/AuthCredentials.java

@@ -132,6 +132,12 @@ public RestorableState<AuthCredentials> capture() {
     }
   }
 
+  /**
+   * Represents service account credentials.
+   *
+   * @see <a href="https://cloud.google.com/docs/authentication#user_accounts_and_service_accounts">
+   *     User accounts and service accounts</a>
+   */
   public static class ServiceAccountAuthCredentials extends AuthCredentials {
 
     private final String account;
@@ -195,6 +201,14 @@ public RestorableState<AuthCredentials> capture() {
     }
   }
 
+  /**
+   * Represents Application Default Credentials, which are credentials that are inferred from the
+   * runtime environment.
+   *
+   * @see <a
+   *     href="https://developers.google.com/identity/protocols/application-default-credentials">
+   *     Google Application Default Credentials</a>
+   */
   public static class ApplicationDefaultAuthCredentials extends AuthCredentials {
 
     private GoogleCredentials googleCredentials;
@@ -243,6 +257,38 @@ public RestorableState<AuthCredentials> capture() {
     }
   }
 
+  /**
+   * A placeholder for credentials to signify that requests sent to the server should not be
+   * authenticated. This is typically useful when using the local service emulators, such as
+   * {@code LocalGcdHelper} and {@code LocalResourceManagerHelper}.
+   */
+  public static class NoAuthCredentials extends AuthCredentials {
+
+    private static final AuthCredentials INSTANCE = new NoAuthCredentials();
+    private static final NoAuthCredentialsState STATE = new NoAuthCredentialsState();
+
+    private static class NoAuthCredentialsState
+        implements RestorableState<AuthCredentials>, Serializable {
+
+      private static final long serialVersionUID = -4022100563954640465L;
+
+      @Override
+      public AuthCredentials restore() {
+        return INSTANCE;
+      }
+    }
+
+    @Override
+    public GoogleCredentials credentials() {
+      return null;
+    }
+
+    @Override
+    public RestorableState<AuthCredentials> capture() {
+      return STATE;
+    }
+  }
+
   public abstract GoogleCredentials credentials();
 
   public static AuthCredentials createForAppEngine() {
@@ -281,6 +327,15 @@ public static ServiceAccountAuthCredentials createFor(String account, PrivateKey
     return new ServiceAccountAuthCredentials(account, privateKey);
   }
 
+  /**
+   * Creates a placeholder denoting that no credentials should be used. This is typically useful
+   * when using the local service emulators, such as {@code LocalGcdHelper} and
+   * {@code LocalResourceManagerHelper}.
+   */
+  public static AuthCredentials noAuth() {
+    return NoAuthCredentials.INSTANCE;
+  }
+
   /**
    * Creates Service Account Credentials given a stream for credentials in JSON format.
    *

gcloud-java-core/src/main/java/com/google/gcloud/ServiceOptions.java

@@ -523,9 +523,10 @@ public RetryParams retryParams() {
    * options.
    */
   public HttpRequestInitializer httpRequestInitializer() {
-    final HttpRequestInitializer delegate = authCredentials() != null
-        ? new HttpCredentialsAdapter(authCredentials().credentials().createScoped(scopes()))
-        : null;
+    final HttpRequestInitializer delegate =
+        authCredentials() != null && authCredentials.credentials() != null
+            ? new HttpCredentialsAdapter(authCredentials().credentials().createScoped(scopes()))
+            : null;
     return new HttpRequestInitializer() {
       @Override
       public void initialize(HttpRequest httpRequest) throws IOException {

gcloud-java-datastore/src/test/java/com/google/gcloud/datastore/DatastoreTest.java

@@ -32,6 +32,7 @@
 import com.google.api.services.datastore.DatastoreV1.RunQueryResponse;
 import com.google.common.collect.Iterators;
 import com.google.common.collect.Lists;
+import com.google.gcloud.AuthCredentials;
 import com.google.gcloud.RetryParams;
 import com.google.gcloud.datastore.Query.ResultType;
 import com.google.gcloud.datastore.StructuredQuery.OrderBy;
@@ -128,6 +129,7 @@ public void setUp() {
     options = DatastoreOptions.builder()
         .projectId(PROJECT_ID)
         .host("http://localhost:" + PORT)
+        .authCredentials(AuthCredentials.noAuth())
         .retryParams(RetryParams.noRetries())
         .build();
     datastore = options.service();

gcloud-java-resourcemanager/src/main/java/com/google/gcloud/resourcemanager/testing/LocalResourceManagerHelper.java

@@ -12,6 +12,7 @@
 import com.google.common.collect.ImmutableMap;
 import com.google.common.collect.ImmutableSet;
 import com.google.common.io.ByteStreams;
+import com.google.gcloud.AuthCredentials;
 import com.google.gcloud.resourcemanager.ResourceManagerOptions;
 
 import com.sun.net.httpserver.Headers;
@@ -550,17 +551,21 @@ private LocalResourceManagerHelper() {
   }
 
   /**
-   * Creates a LocalResourceManagerHelper object that listens to requests on the local machine.
+   * Creates a {@code LocalResourceManagerHelper} object that listens to requests on the local
+   * machine.
    */
   public static LocalResourceManagerHelper create() {
     return new LocalResourceManagerHelper();
   }
 
   /**
-   * Returns a ResourceManagerOptions instance that sets the host to use the mock server.
+   * Returns a {@link ResourceManagerOptions} instance that sets the host to use the mock server.
    */
   public ResourceManagerOptions options() {
-    return ResourceManagerOptions.builder().host("http://localhost:" + port).build();
+    return ResourceManagerOptions.builder()
+        .host("http://localhost:" + port)
+        .authCredentials(AuthCredentials.noAuth())
+        .build();
   }
 
   /**