feat(xds): Add ExternalAuthorizationFilter

.gitignore

@@ -31,6 +31,9 @@ MODULE.bazel.lock
 .gitignore
 bin
 
+# VsCode
+.vscode
+
 # OS X
 .DS_Store
 

core/src/main/java/io/grpc/internal/FailingClientCall.java

@@ -0,0 +1,57 @@
+/*
+ * Copyright 2025 The gRPC Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.internal;
+
+import io.grpc.ClientCall;
+import io.grpc.Metadata;
+import io.grpc.Status;
+import javax.annotation.Nullable;
+
+/**
+ * A {@link ClientCall} that fails immediately upon starting.
+ */
+public final class FailingClientCall<ReqT, RespT> extends ClientCall<ReqT, RespT> {
+
+  private final Status error;
+
+  /**
+   * Creates a new call that will fail with the given error.
+   */
+  public FailingClientCall(Status error) {
+    this.error = error;
+  }
+
+  /**
+   * Immediately fails the call by calling {@link Listener#onClose}.
+   */
+  @Override
+  public void start(Listener<RespT> responseListener, Metadata headers) {
+    responseListener.onClose(error, new Metadata());
+  }
+
+  @Override
+  public void request(int numMessages) {}
+
+  @Override
+  public void cancel(@Nullable String message, @Nullable Throwable cause) {}
+
+  @Override
+  public void halfClose() {}
+
+  @Override
+  public void sendMessage(ReqT message) {}
+}

core/src/test/java/io/grpc/internal/FailingClientCallTest.java

@@ -0,0 +1,76 @@
+/*
+ * Copyright 2016 The gRPC Authors
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package io.grpc.internal;
+
+import static org.junit.Assert.assertEquals;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.verifyNoMoreInteractions;
+
+import io.grpc.ClientCall;
+import io.grpc.Metadata;
+import io.grpc.Status;
+import org.junit.Rule;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.JUnit4;
+import org.mockito.ArgumentCaptor;
+import org.mockito.Mock;
+import org.mockito.junit.MockitoJUnit;
+import org.mockito.junit.MockitoRule;
+
+/** Unit tests for {@link FailingClientCall}. */
+@RunWith(JUnit4.class)
+public class FailingClientCallTest {
+
+  @Rule public final MockitoRule mocks = MockitoJUnit.rule();
+
+  @Mock
+  private ClientCall.Listener<Object> mockListener;
+
+  @Test
+  public void startCallsOnClose() {
+    Status error = Status.UNAVAILABLE.withDescription("test error");
+    FailingClientCall<Object, Object> call = new FailingClientCall<>(error);
+    Metadata metadata = new Metadata();
+    call.start(mockListener, metadata);
+
+    ArgumentCaptor<Metadata> metadataCaptor = ArgumentCaptor.forClass(Metadata.class);
+    verify(mockListener).onClose(eq(error), metadataCaptor.capture());
+    assertEquals(0, metadataCaptor.getValue().keys().size());
+    verifyNoMoreInteractions(mockListener);
+  }
+
+  @Test
+  public void otherMethodsAreNoOps() {
+    Status error = Status.UNAVAILABLE.withDescription("test error");
+    FailingClientCall<Object, Object> call = new FailingClientCall<>(error);
+    Metadata metadata = new Metadata();
+
+    call.start(mockListener, metadata); // Must call start first
+
+    call.request(1);
+    call.cancel("message", new RuntimeException("cause"));
+    call.halfClose();
+    call.sendMessage(new Object());
+
+    ArgumentCaptor<Metadata> metadataCaptor = ArgumentCaptor.forClass(Metadata.class);
+    verify(mockListener).onClose(eq(error), metadataCaptor.capture());
+    assertEquals(0, metadataCaptor.getValue().keys().size());
+    verifyNoMoreInteractions(mockListener);
+  }
+}