[ggj][codegen] fix: map proto.Empty RPC types to void in ServiceClient

src/main/java/com/google/api/generator/gapic/composer/ServiceClientClassComposer.java

@@ -539,28 +539,35 @@ private static List<MethodDefinition> createMethodVariants(
               .setVariableExpr(requestVarExpr)
               .setValueExpr(requestBuilderExpr)
               .build();
-      List<Statement> statements = Arrays.asList(ExprStatement.withExpr(requestAssignmentExpr));
 
-      // Return expression.
-      MethodInvocationExpr returnExpr =
+      List<Statement> statements = new ArrayList<>();
+      statements.add(ExprStatement.withExpr(requestAssignmentExpr));
+
+      MethodInvocationExpr rpcInvocationExpr =
           MethodInvocationExpr.builder()
               .setMethodName(String.format(method.hasLro() ? "%sAsync" : "%s", methodName))
               .setArguments(Arrays.asList(requestVarExpr.toBuilder().setIsDecl(false).build()))
               .setReturnType(methodOutputType)
               .build();
 
-      javaMethods.add(
+      MethodDefinition.Builder methodVariantBuilder =
           MethodDefinition.builder()
               .setHeaderCommentStatements(
                   ServiceClientCommentComposer.createRpcMethodHeaderComment(method, signature))
               .setScope(ScopeNode.PUBLIC)
               .setIsFinal(true)
-              .setReturnType(methodOutputType)
               .setName(String.format(method.hasLro() ? "%sAsync" : "%s", methodName))
-              .setArguments(arguments)
-              .setBody(statements)
-              .setReturnExpr(returnExpr)
-              .build());
+              .setArguments(arguments);
+
+      if (isProtoEmptyType(methodOutputType)) {
+        statements.add(ExprStatement.withExpr(rpcInvocationExpr));
+        methodVariantBuilder = methodVariantBuilder.setReturnType(TypeNode.VOID);
+      } else {
+        methodVariantBuilder =
+            methodVariantBuilder.setReturnType(methodOutputType).setReturnExpr(rpcInvocationExpr);
+      }
+      methodVariantBuilder = methodVariantBuilder.setBody(statements);
+      javaMethods.add(methodVariantBuilder.build());
     }
 
     return javaMethods;
@@ -600,25 +607,34 @@ private static MethodDefinition createMethodDefaultMethod(
       callableMethodName = String.format(OPERATION_CALLABLE_NAME_PATTERN, methodName);
     }
 
-    MethodInvocationExpr methodReturnExpr =
+    MethodInvocationExpr callableMethodExpr =
         MethodInvocationExpr.builder().setMethodName(callableMethodName).build();
-    methodReturnExpr =
+    callableMethodExpr =
         MethodInvocationExpr.builder()
             .setMethodName(method.hasLro() ? "futureCall" : "call")
             .setArguments(Arrays.asList(requestArgVarExpr.toBuilder().setIsDecl(false).build()))
-            .setExprReferenceExpr(methodReturnExpr)
+            .setExprReferenceExpr(callableMethodExpr)
             .setReturnType(methodOutputType)
             .build();
-    return MethodDefinition.builder()
-        .setHeaderCommentStatements(
-            ServiceClientCommentComposer.createRpcMethodHeaderComment(method))
-        .setScope(ScopeNode.PUBLIC)
-        .setIsFinal(true)
-        .setReturnType(methodOutputType)
-        .setName(String.format(method.hasLro() ? "%sAsync" : "%s", methodName))
-        .setArguments(Arrays.asList(requestArgVarExpr))
-        .setReturnExpr(methodReturnExpr)
-        .build();
+    MethodDefinition.Builder methodBuilder =
+        MethodDefinition.builder()
+            .setHeaderCommentStatements(
+                ServiceClientCommentComposer.createRpcMethodHeaderComment(method))
+            .setScope(ScopeNode.PUBLIC)
+            .setIsFinal(true)
+            .setName(String.format(method.hasLro() ? "%sAsync" : "%s", methodName))
+            .setArguments(Arrays.asList(requestArgVarExpr));
+
+    if (isProtoEmptyType(methodOutputType)) {
+      methodBuilder =
+          methodBuilder
+              .setBody(Arrays.asList(ExprStatement.withExpr(callableMethodExpr)))
+              .setReturnType(TypeNode.VOID);
+    } else {
+      methodBuilder =
+          methodBuilder.setReturnExpr(callableMethodExpr).setReturnType(methodOutputType);
+    }
+    return methodBuilder.build();
   }
 
   private static MethodDefinition createLroCallableMethod(
@@ -1537,4 +1553,9 @@ private static String getCallableName(CallableMethodKind kind, String rawMethodN
     }
     return String.format(CALLABLE_NAME_PATTERN, rawMethodName);
   }
+
+  private static boolean isProtoEmptyType(TypeNode type) {
+    return type.reference().pakkage().equals("com.google.protobuf")
+        && type.reference().name().equals("Empty");
+  }
 }

src/main/java/com/google/api/generator/gapic/composer/ServiceClientTestClassComposer.java

@@ -650,11 +650,17 @@ private static MethodDefinition createRpcTestMethod(
               .setReturnType(rpcJavaMethodInvocationExpr.type())
               .build();
     }
-    methodExprs.add(
-        AssignmentExpr.builder()
-            .setVariableExpr(actualResponseVarExpr.toBuilder().setIsDecl(true).build())
-            .setValueExpr(rpcJavaMethodInvocationExpr)
-            .build());
+
+    boolean returnsVoid = isProtoEmptyType(methodOutputType);
+    if (returnsVoid) {
+      methodExprs.add(rpcJavaMethodInvocationExpr);
+    } else {
+      methodExprs.add(
+          AssignmentExpr.builder()
+              .setVariableExpr(actualResponseVarExpr.toBuilder().setIsDecl(true).build())
+              .setValueExpr(rpcJavaMethodInvocationExpr)
+              .build());
+    }
 
     if (method.isPaged()) {
       // Assign the resources variable.
@@ -747,7 +753,7 @@ private static MethodDefinition createRpcTestMethod(
               .setMethodName("assertEquals")
               .setArguments(expectedPagedResponseExpr, actualPagedResponseExpr)
               .build());
-    } else {
+    } else if (!returnsVoid) {
       methodExprs.add(
           MethodInvocationExpr.builder()
               .setStaticReferenceType(STATIC_TYPES.get("Assert"))
@@ -1898,4 +1904,9 @@ private static String getServiceSettingsClassName(String serviceName) {
   private static String getMockServiceVarName(String serviceName) {
     return String.format(MOCK_SERVICE_VAR_NAME_PATTERN, serviceName);
   }
+
+  private static boolean isProtoEmptyType(TypeNode type) {
+    return type.reference().pakkage().equals("com.google.protobuf")
+        && type.reference().name().equals("Empty");
+  }
 }

src/test/java/com/google/api/generator/gapic/composer/goldens/IdentityClient.golden

@@ -257,12 +257,12 @@ public class IdentityClient implements BackgroundResource {
    * @param name
    * @throws com.google.api.gax.rpc.ApiException if the remote call fails
    */
-  public final Empty deleteUser(UserName name) {
+  public final void deleteUser(UserName name) {
     DeleteUserRequest request =
         DeleteUserRequest.newBuilder()
             .setName(Objects.isNull(name) ? null : name.toString())
             .build();
-    return deleteUser(request);
+    deleteUser(request);
   }
 
   // AUTO-GENERATED DOCUMENTATION AND METHOD.
@@ -272,9 +272,9 @@ public class IdentityClient implements BackgroundResource {
    * @param name
    * @throws com.google.api.gax.rpc.ApiException if the remote call fails
    */
-  public final Empty deleteUser(String name) {
+  public final void deleteUser(String name) {
     DeleteUserRequest request = DeleteUserRequest.newBuilder().setName(name).build();
-    return deleteUser(request);
+    deleteUser(request);
   }
 
   // AUTO-GENERATED DOCUMENTATION AND METHOD.
@@ -284,8 +284,8 @@ public class IdentityClient implements BackgroundResource {
    * @param request The request object containing all of the parameters for the API call.
    * @throws com.google.api.gax.rpc.ApiException if the remote call fails
    */
-  public final Empty deleteUser(DeleteUserRequest request) {
-    return deleteUserCallable().call(request);
+  public final void deleteUser(DeleteUserRequest request) {
+    deleteUserCallable().call(request);
   }
 
   // AUTO-GENERATED DOCUMENTATION AND METHOD.

src/test/java/com/google/api/generator/gapic/composer/goldens/LoggingClientTest.golden

@@ -81,8 +81,7 @@ public class LoggingServiceV2ClientTest {
 
     LogName logName = LogName.ofProjectLogName("[PROJECT]", "[LOG]");
 
-    Empty actualResponse = client.deleteLog(logName);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.deleteLog(logName);
 
     List<AbstractMessage> actualRequests = mockLoggingServiceV2.getRequests();
     Assert.assertEquals(1, actualRequests.size());
@@ -116,8 +115,7 @@ public class LoggingServiceV2ClientTest {
 
     String logName = "log_name2013526694";
 
-    Empty actualResponse = client.deleteLog(logName);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.deleteLog(logName);
 
     List<AbstractMessage> actualRequests = mockLoggingServiceV2.getRequests();
     Assert.assertEquals(1, actualRequests.size());

src/test/java/com/google/api/generator/gapic/composer/goldens/SubscriberClientTest.golden

@@ -557,8 +557,7 @@ public class SubscriberClientTest {
 
     SubscriptionName subscription = SubscriptionName.of("[PROJECT]", "[SUBSCRIPTION]");
 
-    Empty actualResponse = client.deleteSubscription(subscription);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.deleteSubscription(subscription);
 
     List<AbstractMessage> actualRequests = mockSubscriber.getRequests();
     Assert.assertEquals(1, actualRequests.size());
@@ -592,8 +591,7 @@ public class SubscriberClientTest {
 
     String subscription = "subscription341203229";
 
-    Empty actualResponse = client.deleteSubscription(subscription);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.deleteSubscription(subscription);
 
     List<AbstractMessage> actualRequests = mockSubscriber.getRequests();
     Assert.assertEquals(1, actualRequests.size());
@@ -629,8 +627,7 @@ public class SubscriberClientTest {
     List<String> ackIds = new ArrayList<>();
     int ackDeadlineSeconds = 2135351438;
 
-    Empty actualResponse = client.modifyAckDeadline(subscription, ackIds, ackDeadlineSeconds);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.modifyAckDeadline(subscription, ackIds, ackDeadlineSeconds);
 
     List<AbstractMessage> actualRequests = mockSubscriber.getRequests();
     Assert.assertEquals(1, actualRequests.size());
@@ -670,8 +667,7 @@ public class SubscriberClientTest {
     List<String> ackIds = new ArrayList<>();
     int ackDeadlineSeconds = 2135351438;
 
-    Empty actualResponse = client.modifyAckDeadline(subscription, ackIds, ackDeadlineSeconds);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.modifyAckDeadline(subscription, ackIds, ackDeadlineSeconds);
 
     List<AbstractMessage> actualRequests = mockSubscriber.getRequests();
     Assert.assertEquals(1, actualRequests.size());
@@ -710,8 +706,7 @@ public class SubscriberClientTest {
     SubscriptionName subscription = SubscriptionName.of("[PROJECT]", "[SUBSCRIPTION]");
     List<String> ackIds = new ArrayList<>();
 
-    Empty actualResponse = client.acknowledge(subscription, ackIds);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.acknowledge(subscription, ackIds);
 
     List<AbstractMessage> actualRequests = mockSubscriber.getRequests();
     Assert.assertEquals(1, actualRequests.size());
@@ -748,8 +743,7 @@ public class SubscriberClientTest {
     String subscription = "subscription341203229";
     List<String> ackIds = new ArrayList<>();
 
-    Empty actualResponse = client.acknowledge(subscription, ackIds);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.acknowledge(subscription, ackIds);
 
     List<AbstractMessage> actualRequests = mockSubscriber.getRequests();
     Assert.assertEquals(1, actualRequests.size());
@@ -939,8 +933,7 @@ public class SubscriberClientTest {
     SubscriptionName subscription = SubscriptionName.of("[PROJECT]", "[SUBSCRIPTION]");
     PushConfig pushConfig = PushConfig.newBuilder().build();
 
-    Empty actualResponse = client.modifyPushConfig(subscription, pushConfig);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.modifyPushConfig(subscription, pushConfig);
 
     List<AbstractMessage> actualRequests = mockSubscriber.getRequests();
     Assert.assertEquals(1, actualRequests.size());
@@ -977,8 +970,7 @@ public class SubscriberClientTest {
     String subscription = "subscription341203229";
     PushConfig pushConfig = PushConfig.newBuilder().build();
 
-    Empty actualResponse = client.modifyPushConfig(subscription, pushConfig);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.modifyPushConfig(subscription, pushConfig);
 
     List<AbstractMessage> actualRequests = mockSubscriber.getRequests();
     Assert.assertEquals(1, actualRequests.size());
@@ -1397,8 +1389,7 @@ public class SubscriberClientTest {
 
     SnapshotName snapshot = SnapshotName.of("[PROJECT]", "[SNAPSHOT]");
 
-    Empty actualResponse = client.deleteSnapshot(snapshot);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.deleteSnapshot(snapshot);
 
     List<AbstractMessage> actualRequests = mockSubscriber.getRequests();
     Assert.assertEquals(1, actualRequests.size());
@@ -1432,8 +1423,7 @@ public class SubscriberClientTest {
 
     String snapshot = "snapshot284874180";
 
-    Empty actualResponse = client.deleteSnapshot(snapshot);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.deleteSnapshot(snapshot);
 
     List<AbstractMessage> actualRequests = mockSubscriber.getRequests();
     Assert.assertEquals(1, actualRequests.size());

src/test/java/com/google/api/generator/gapic/composer/goldens/TestingClientTest.golden

@@ -212,8 +212,7 @@ public class TestingClientTest {
     DeleteSessionRequest request =
         DeleteSessionRequest.newBuilder().setName(SessionName.of("[SESSION]").toString()).build();
 
-    Empty actualResponse = client.deleteSession(request);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.deleteSession(request);
 
     List<AbstractMessage> actualRequests = mockTesting.getRequests();
     Assert.assertEquals(1, actualRequests.size());
@@ -425,8 +424,7 @@ public class TestingClientTest {
             .setName(TestName.of("[SESSION]", "[SHARD_ID]", "[TEST_ID]").toString())
             .build();
 
-    Empty actualResponse = client.deleteTest(request);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.deleteTest(request);
 
     List<AbstractMessage> actualRequests = mockTesting.getRequests();
     Assert.assertEquals(1, actualRequests.size());

test/integration/goldens/asset/AssetServiceClient.java

@@ -429,12 +429,12 @@ public final UnaryCallable<UpdateFeedRequest, Feed> updateFeedCallable() {
    *     organizations/organization_number/feeds/feed_id
    * @throws com.google.api.gax.rpc.ApiException if the remote call fails
    */
-  public final Empty deleteFeed(FeedName name) {
+  public final void deleteFeed(FeedName name) {
     DeleteFeedRequest request =
         DeleteFeedRequest.newBuilder()
             .setName(Objects.isNull(name) ? null : name.toString())
             .build();
-    return deleteFeed(request);
+    deleteFeed(request);
   }
 
   // AUTO-GENERATED DOCUMENTATION AND METHOD.
@@ -448,9 +448,9 @@ public final Empty deleteFeed(FeedName name) {
    *     organizations/organization_number/feeds/feed_id
    * @throws com.google.api.gax.rpc.ApiException if the remote call fails
    */
-  public final Empty deleteFeed(String name) {
+  public final void deleteFeed(String name) {
     DeleteFeedRequest request = DeleteFeedRequest.newBuilder().setName(name).build();
-    return deleteFeed(request);
+    deleteFeed(request);
   }
 
   // AUTO-GENERATED DOCUMENTATION AND METHOD.
@@ -462,8 +462,8 @@ public final Empty deleteFeed(String name) {
    * @param request The request object containing all of the parameters for the API call.
    * @throws com.google.api.gax.rpc.ApiException if the remote call fails
    */
-  public final Empty deleteFeed(DeleteFeedRequest request) {
-    return deleteFeedCallable().call(request);
+  public final void deleteFeed(DeleteFeedRequest request) {
+    deleteFeedCallable().call(request);
   }
 
   // AUTO-GENERATED DOCUMENTATION AND METHOD.

test/integration/goldens/asset/AssetServiceClientTest.java

@@ -414,8 +414,7 @@ public void deleteFeedTest() throws Exception {
 
     FeedName name = FeedName.ofProjectFeedName("[PROJECT]", "[FEED]");
 
-    Empty actualResponse = client.deleteFeed(name);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.deleteFeed(name);
 
     List<AbstractMessage> actualRequests = mockAssetService.getRequests();
     Assert.assertEquals(1, actualRequests.size());
@@ -449,8 +448,7 @@ public void deleteFeedTest2() throws Exception {
 
     String name = "name3373707";
 
-    Empty actualResponse = client.deleteFeed(name);
-    Assert.assertEquals(expectedResponse, actualResponse);
+    client.deleteFeed(name);
 
     List<AbstractMessage> actualRequests = mockAssetService.getRequests();
     Assert.assertEquals(1, actualRequests.size());