feat: implement snapshot-integrated custom LRO error parsing (POC 3)

java-compute/google-cloud-compute/src/main/java/com/google/cloud/compute/v1/stub/ComputeLroErrorParser.java

@@ -0,0 +1,73 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * 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
+ *
+ *      https://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 com.google.cloud.compute.v1.stub;
+
+import com.google.api.core.BetaApi;
+import com.google.api.gax.httpjson.HttpJsonLroErrorParser;
+import com.google.api.gax.rpc.ErrorDetails;
+import com.google.cloud.compute.v1.Errors;
+import com.google.cloud.compute.v1.Operation;
+import com.google.protobuf.Any;
+import com.google.rpc.ErrorInfo;
+import java.util.ArrayList;
+import java.util.List;
+
+@BetaApi("The surface for custom LRO error parsing is not stable yet and may change.")
+class ComputeLroErrorParser implements HttpJsonLroErrorParser {
+
+  @Override
+  public ErrorDetails parse(Object response) {
+    if (!(response instanceof Operation)) {
+      return null;
+    }
+    Operation operation = ((Operation) response);
+    if (!operation.hasError()) {
+      return null;
+    }
+    List<Any> rawErrorMessages = new ArrayList<>();
+    for (Errors error : operation.getError().getErrorsList()) {
+      ErrorInfo errorInfo =
+          ErrorInfo.newBuilder()
+              .setReason(error.getCode())
+              .setDomain("googleapis.com")
+              .putMetadata("message", error.getMessage())
+              .putMetadata("location", error.getLocation())
+              .build();
+      rawErrorMessages.add(Any.pack(errorInfo));
+    }
+    return ErrorDetails.builder().setRawErrorMessages(rawErrorMessages).build();
+  }
+
+  @Override
+  public String parseErrorMessage(Object response) {
+    if (!(response instanceof Operation)) {
+      return null;
+    }
+    Operation operation = ((Operation) response);
+    if (!operation.hasError() || operation.getError().getErrorsCount() == 0) {
+      return null;
+    }
+    StringBuilder sb = new StringBuilder();
+    for (Errors error : operation.getError().getErrorsList()) {
+      if (sb.length() > 0) {
+        sb.append("; ");
+      }
+      sb.append(error.getCode()).append(": ").append(error.getMessage());
+    }
+    return sb.toString();
+  }
+}

java-compute/google-cloud-compute/src/main/java/com/google/cloud/compute/v1/stub/HttpJsonAddressesStub.java

@@ -178,6 +178,7 @@ public class HttpJsonAddressesStub extends AddressesStub {
                     .setDone(Status.DONE.equals(response.getStatus()))
                     .setResponse(response)
                     .setError(response.getHttpErrorStatusCode(), response.getHttpErrorMessage())
+                    .setErrorParser(new ComputeLroErrorParser())
                     .build();
               })
           .build();
@@ -264,6 +265,7 @@ public class HttpJsonAddressesStub extends AddressesStub {
                     .setDone(Status.DONE.equals(response.getStatus()))
                     .setResponse(response)
                     .setError(response.getHttpErrorStatusCode(), response.getHttpErrorMessage())
+                    .setErrorParser(new ComputeLroErrorParser())
                     .build();
               })
           .build();
@@ -369,6 +371,7 @@ public class HttpJsonAddressesStub extends AddressesStub {
                     .setDone(Status.DONE.equals(response.getStatus()))
                     .setResponse(response)
                     .setError(response.getHttpErrorStatusCode(), response.getHttpErrorMessage())
+                    .setErrorParser(new ComputeLroErrorParser())
                     .build();
               })
           .build();
@@ -426,6 +429,7 @@ public class HttpJsonAddressesStub extends AddressesStub {
                         .setDone(Status.DONE.equals(response.getStatus()))
                         .setResponse(response)
                         .setError(response.getHttpErrorStatusCode(), response.getHttpErrorMessage())
+                        .setErrorParser(new ComputeLroErrorParser())
                         .build();
                   })
               .build();

java-compute/google-cloud-compute/src/main/java/com/google/cloud/compute/v1/stub/HttpJsonRegionOperationsStub.java

@@ -143,6 +143,7 @@ public class HttpJsonRegionOperationsStub extends RegionOperationsStub {
                         .setDone(Status.DONE.equals(response.getStatus()))
                         .setResponse(response)
                         .setError(response.getHttpErrorStatusCode(), response.getHttpErrorMessage())
+                        .setErrorParser(new ComputeLroErrorParser())
                         .build();
                   })
               .setPollingRequestFactory(

java-showcase/gapic-showcase/src/test/java/com/google/showcase/v1beta1/it/ITLongRunningOperation.java

@@ -20,13 +20,19 @@
 
 import com.google.api.gax.longrunning.OperationFuture;
 import com.google.api.gax.retrying.RetrySettings;
+import com.google.api.gax.rpc.ApiException;
+import com.google.protobuf.Any;
 import com.google.protobuf.Timestamp;
+import com.google.rpc.Code;
+import com.google.rpc.ErrorInfo;
+import com.google.rpc.Status;
 import com.google.showcase.v1beta1.EchoClient;
 import com.google.showcase.v1beta1.WaitMetadata;
 import com.google.showcase.v1beta1.WaitRequest;
 import com.google.showcase.v1beta1.WaitResponse;
 import com.google.showcase.v1beta1.it.util.TestClientInitializer;
 import java.util.concurrent.CancellationException;
+import java.util.concurrent.ExecutionException;
 import java.util.concurrent.TimeUnit;
 import org.junit.jupiter.api.Test;
 import org.threeten.bp.Duration;
@@ -193,4 +199,33 @@ void testHttpJson_LROUnsuccessfulResponse_exceedsTotalTimeout_throwsDeadlineExce
           TestClientInitializer.AWAIT_TERMINATION_SECONDS, TimeUnit.SECONDS);
     }
   }
+
+  @Test
+  void testGRPC_LROErrorResponse_propagatesErrorDetails() throws Exception {
+    EchoClient grpcClient = TestClientInitializer.createGrpcEchoClient();
+    try {
+      ErrorInfo errorInfo =
+          ErrorInfo.newBuilder().setReason("TEST_REASON").setDomain("googleapis.com").build();
+      Status status =
+          Status.newBuilder()
+              .setCode(Code.ALREADY_EXISTS_VALUE)
+              .setMessage("The resource already exists")
+              .addDetails(Any.pack(errorInfo))
+              .build();
+      WaitRequest waitRequest = WaitRequest.newBuilder().setError(status).build();
+      OperationFuture<WaitResponse, WaitMetadata> operationFuture =
+          grpcClient.waitOperationCallable().futureCall(waitRequest);
+      ExecutionException exception = assertThrows(ExecutionException.class, operationFuture::get);
+      assertThat(exception.getCause()).isInstanceOf(ApiException.class);
+      ApiException apiException = (ApiException) exception.getCause();
+
+      // Verify that error details are successfully propagated
+      assertThat(apiException.getErrorDetails()).isNotNull();
+      assertThat(apiException.getErrorDetails().getErrorInfo()).isEqualTo(errorInfo);
+    } finally {
+      grpcClient.close();
+      grpcClient.awaitTermination(
+          TestClientInitializer.AWAIT_TERMINATION_SECONDS, TimeUnit.SECONDS);
+    }
+  }
 }

librarian.yaml

@@ -1231,6 +1231,9 @@ libraries:
         java:
           omit_common_resources: true
     keep:
+      - google-cloud-compute/src/main/java/com/google/cloud/compute/v1/stub/ComputeLroErrorParser.java
+      - google-cloud-compute/src/main/java/com/google/cloud/compute/v1/stub/HttpJsonAddressesStub.java
+      - google-cloud-compute/src/main/java/com/google/cloud/compute/v1/stub/HttpJsonRegionOperationsStub.java
       - google-cloud-compute/src/test/java/com/google/cloud/compute/v1/integration/BaseTest.java
       - google-cloud-compute/src/test/java/com/google/cloud/compute/v1/integration/ITComputeGoldenSignals.java
       - google-cloud-compute/src/test/java/com/google/cloud/compute/v1/integration/ITPaginationTest.java

sdk-platform-java/gapic-generator-java/src/main/java/com/google/api/generator/gapic/composer/rest/HttpJsonServiceStubClassComposer.java

@@ -126,7 +126,9 @@ private static TypeStore createStaticTypes() {
 
   @Override
   protected boolean generateOperationsStubLogic(Service service) {
-    return service.hasLroMethods();
+    return service.hasLroMethods()
+        && (service.pakkage().startsWith("com.google.cloud.compute.v1")
+            && !service.pakkage().startsWith("com.google.cloud.compute.v1small"));
   }
 
   @Override
@@ -170,7 +172,7 @@ protected Statement createMethodDescriptorVariableDecl(
           methodMaker
               .apply(
                   "setOperationSnapshotFactory",
-                  setOperationSnapshotFactoryExpr(protoMethod, messageTypes))
+                  setOperationSnapshotFactoryExpr(service, protoMethod, messageTypes))
               .apply(expr);
     }
 
@@ -453,7 +455,7 @@ private MethodInvocationExpr getExpr(VariableExpr var, String num) {
   }
 
   private List<Expr> setOperationSnapshotFactoryExpr(
-      Method protoMethod, Map<String, Message> messageTypes) {
+      Service service, Method protoMethod, Map<String, Message> messageTypes) {
 
     // Generate input variables for create()
     VariableExpr requestVarExpr =
@@ -598,6 +600,21 @@ private List<Expr> setOperationSnapshotFactoryExpr(
               .apply("setError", Arrays.asList(getHttpErrorStatusCodeExpr, getHttpErrorMessageExpr))
               .apply(newBuilderExpr);
 
+      if (service.pakkage().startsWith("com.google.cloud.compute.v1")
+          && !service.pakkage().startsWith("com.google.cloud.compute.v1small")) {
+        TypeNode parserType =
+            TypeNode.withReference(
+                VaporReference.builder()
+                    .setName("ComputeLroErrorParser")
+                    .setPakkage(service.pakkage() + ".stub")
+                    .build());
+        Expr newParserExpr = NewObjectExpr.builder().setType(parserType).build();
+        newBuilderExpr =
+            methodMaker
+                .apply("setErrorParser", Collections.singletonList(newParserExpr))
+                .apply(newBuilderExpr);
+      }
+
       buildExpr =
           MethodInvocationExpr.builder()
               .setExprReferenceExpr(newBuilderExpr)

sdk-platform-java/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/GrpcOperationSnapshot.java

@@ -30,6 +30,7 @@
 package com.google.api.gax.grpc;
 
 import com.google.api.gax.longrunning.OperationSnapshot;
+import com.google.api.gax.rpc.ErrorDetails;
 import com.google.api.gax.rpc.StatusCode;
 import com.google.longrunning.Operation;
 import io.grpc.Status;
@@ -79,6 +80,14 @@ public String getErrorMessage() {
     return operation.getError().getMessage();
   }
 
+  /** {@inheritDoc} */
+  @Override
+  public ErrorDetails getErrorDetails() {
+    return ErrorDetails.builder()
+        .setRawErrorMessages(operation.getError().getDetailsList())
+        .build();
+  }
+
   public static GrpcOperationSnapshot create(Operation operation) {
     return new GrpcOperationSnapshot(operation);
   }

sdk-platform-java/gax-java/gax-grpc/src/main/java/com/google/api/gax/grpc/ProtoOperationTransformers.java

@@ -63,7 +63,8 @@ public ResponseT apply(OperationSnapshot operationSnapshot) {
                 + operationSnapshot.getErrorMessage(),
             null,
             operationSnapshot.getErrorCode(),
-            false);
+            false,
+            operationSnapshot.getErrorDetails());
       }
 
       if (!(operationSnapshot.getResponse() instanceof Any)) {

sdk-platform-java/gax-java/gax-grpc/src/test/java/com/google/api/gax/grpc/ProtoOperationTransformersTest.java

@@ -34,15 +34,17 @@
 import com.google.api.gax.grpc.ProtoOperationTransformers.MetadataTransformer;
 import com.google.api.gax.grpc.ProtoOperationTransformers.ResponseTransformer;
 import com.google.api.gax.longrunning.OperationSnapshot;
+import com.google.api.gax.rpc.ErrorDetails;
 import com.google.api.gax.rpc.UnavailableException;
 import com.google.api.gax.rpc.UnknownException;
 import com.google.common.truth.Truth;
 import com.google.longrunning.Operation;
 import com.google.protobuf.Any;
+import com.google.rpc.ErrorInfo;
 import com.google.rpc.Status;
-import com.google.type.Color;
 import com.google.type.Money;
 import io.grpc.Status.Code;
+import java.util.Collections;
 import org.junit.jupiter.api.Test;
 
 class ProtoOperationTransformersTest {
@@ -64,11 +66,13 @@ void testAnyResponseTransformer_exception() {
     OperationSnapshot operationSnapshot =
         GrpcOperationSnapshot.create(
             Operation.newBuilder().setResponse(Any.pack(inputMoney)).setError(status).build());
-    Exception exception =
+    UnavailableException exception =
         assertThrows(UnavailableException.class, () -> transformer.apply(operationSnapshot));
     Truth.assertThat(exception)
         .hasMessageThat()
         .contains("failed with status = GrpcStatusCode{transportCode=UNAVAILABLE}");
+    Truth.assertThat(exception.getErrorDetails())
+        .isEqualTo(ErrorDetails.builder().setRawErrorMessages(Collections.emptyList()).build());
   }
 
   @Test
@@ -78,7 +82,7 @@ void testAnyResponseTransformer_mismatchedTypes() {
     OperationSnapshot operationSnapshot =
         GrpcOperationSnapshot.create(
             Operation.newBuilder()
-                .setResponse(Any.pack(Color.getDefaultInstance()))
+                .setResponse(Any.pack(ErrorInfo.getDefaultInstance()))
                 .setError(status)
                 .build());
     Exception exception =
@@ -103,11 +107,32 @@ void testAnyMetadataTransformer_mismatchedTypes() {
     OperationSnapshot operationSnapshot =
         GrpcOperationSnapshot.create(
             Operation.newBuilder()
-                .setMetadata(Any.pack(Color.getDefaultInstance()))
+                .setMetadata(Any.pack(ErrorInfo.getDefaultInstance()))
                 .setError(status)
                 .build());
     Exception exception =
         assertThrows(UnknownException.class, () -> transformer.apply(operationSnapshot));
     Truth.assertThat(exception).hasMessageThat().contains("encountered a problem unpacking it");
   }
+
+  @Test
+  void testAnyResponseTransformer_exceptionWithErrorDetails() {
+    ResponseTransformer<Money> transformer = ResponseTransformer.create(Money.class);
+    Money inputMoney = Money.newBuilder().setCurrencyCode("USD").build();
+    ErrorInfo errorInfo =
+        ErrorInfo.newBuilder().setReason("TEST_REASON").setDomain("googleapis.com").build();
+    Status status =
+        Status.newBuilder()
+            .setCode(Code.UNAVAILABLE.value())
+            .addDetails(Any.pack(errorInfo))
+            .build();
+    OperationSnapshot operationSnapshot =
+        GrpcOperationSnapshot.create(
+            Operation.newBuilder().setResponse(Any.pack(inputMoney)).setError(status).build());
+
+    UnavailableException exception =
+        assertThrows(UnavailableException.class, () -> transformer.apply(operationSnapshot));
+    Truth.assertThat(exception.getErrorDetails()).isNotNull();
+    Truth.assertThat(exception.getErrorDetails().getErrorInfo()).isEqualTo(errorInfo);
+  }
 }

sdk-platform-java/gax-java/gax-httpjson/src/main/java/com/google/api/gax/httpjson/HttpJsonLroErrorParser.java

@@ -0,0 +1,46 @@
+/*
+ * Copyright 2026 Google LLC
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google LLC nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+package com.google.api.gax.httpjson;
+
+import com.google.api.core.BetaApi;
+import com.google.api.gax.rpc.ErrorDetails;
+import org.jspecify.annotations.NullMarked;
+import org.jspecify.annotations.Nullable;
+
+@NullMarked
+@BetaApi("The surface for custom LRO error parsing is not stable yet and may change.")
+public interface HttpJsonLroErrorParser {
+  /** Parses custom LRO response object into standard ErrorDetails. */
+  @Nullable ErrorDetails parse(Object response);
+
+  /** Concatenates custom LRO response errors into a single descriptive message. */
+  @Nullable String parseErrorMessage(Object response);
+}