fix: allow empty services and java keywords as a method names

BUILD.bazel

@@ -192,6 +192,14 @@ GOLDEN_UPDATING_UNIT_TESTS = [
     "com.google.api.generator.gapic.composer.grpc.ServiceSettingsClassComposerTest",
     "com.google.api.generator.gapic.composer.grpc.ServiceStubClassComposerTest",
     "com.google.api.generator.gapic.composer.grpc.ServiceStubSettingsClassComposerTest",
+    "com.google.api.generator.gapic.composer.grpcrest.GrpcServiceCallableFactoryClassComposerTest",
+    "com.google.api.generator.gapic.composer.grpcrest.GrpcServiceStubClassComposerTest",
+    "com.google.api.generator.gapic.composer.grpcrest.HttpJsonServiceCallableFactoryClassComposerTest",
+    "com.google.api.generator.gapic.composer.grpcrest.HttpJsonServiceClientTestClassComposerTest",
+    "com.google.api.generator.gapic.composer.grpcrest.HttpJsonServiceStubClassComposerTest",
+    "com.google.api.generator.gapic.composer.grpcrest.ServiceClientClassComposerTest",
+    "com.google.api.generator.gapic.composer.grpcrest.ServiceClientTestClassComposerTest",
+    "com.google.api.generator.gapic.composer.grpcrest.ServiceSettingsClassComposerTest",
     "com.google.api.generator.gapic.composer.resourcename.ResourceNameHelperClassComposerTest",
     "com.google.api.generator.gapic.composer.rest.HttpJsonServiceCallableFactoryClassComposerTest",
     "com.google.api.generator.gapic.composer.rest.HttpJsonServiceStubClassComposerTest",

src/main/java/com/google/api/generator/gapic/composer/common/AbstractServiceStubSettingsClassComposer.java

@@ -392,8 +392,7 @@ private static List<CommentStatement> createClassHeaderComments(
                     .filter(m -> m.stream() == Stream.NONE && !m.hasLro() && !m.isPaged())
                     .findFirst()
                     .orElse(service.methods().get(0)));
-    Optional<String> methodNameOpt =
-        methodOpt.isPresent() ? Optional.of(methodOpt.get().name()) : Optional.empty();
+    Optional<String> methodNameOpt = methodOpt.map(Method::name);
     Optional<Sample> sampleCode =
         SettingsSampleComposer.composeSettingsSample(
             methodNameOpt, ClassNames.getServiceSettingsClassName(service), classType);
@@ -437,7 +436,7 @@ private static Map<String, VariableExpr> createMethodSettingsClassMemberVarExprs
           !Objects.isNull(serviceConfig) && serviceConfig.hasBatchingSetting(service, method);
       TypeNode settingsType =
           getCallSettingsType(method, typeStore, hasBatchingSettings, isNestedClass);
-      String varName = JavaStyle.toLowerCamelCase(String.format("%sSettings", method.name()));
+      String varName = String.format("%sSettings", JavaStyle.toLowerCamelCase(method.name()));
       if (method.isDeprecated()) {
         deprecatedSettingVarNames.add(varName);
       }

src/main/java/com/google/api/generator/gapic/composer/samplecode/ServiceClientHeaderSampleComposer.java

@@ -51,13 +51,18 @@ public static Sample composeClassHeaderSample(
       TypeNode clientType,
       Map<String, ResourceName> resourceNames,
       Map<String, Message> messageTypes) {
+    if (service.methods().isEmpty()) {
+      return ServiceClientMethodSampleComposer.composeEmptyServiceSample(clientType);
+    }
+
     // Use the first pure unary RPC method's sample code as showcase, if no such method exists, use
     // the first method in the service's methods list.
     Method method =
         service.methods().stream()
             .filter(m -> m.stream() == Method.Stream.NONE && !m.hasLro() && !m.isPaged())
             .findFirst()
             .orElse(service.methods().get(0));
+
     if (method.stream() == Method.Stream.NONE) {
       if (method.methodSignatures().isEmpty()) {
         return ServiceClientMethodSampleComposer.composeCanonicalSample(

src/main/java/com/google/api/generator/gapic/composer/samplecode/ServiceClientMethodSampleComposer.java

@@ -42,6 +42,36 @@
 import java.util.stream.Collectors;
 
 public class ServiceClientMethodSampleComposer {
+  // Creates an example for an empty service (no API methods), which is a corner case but can
+  // happen. Generated example will only show how to instantiate the client class but will not call
+  // any API methods (because there are no API methods).
+  public static Sample composeEmptyServiceSample(TypeNode clientType) {
+    VariableExpr clientVarExpr =
+        VariableExpr.withVariable(
+            Variable.builder()
+                .setName(JavaStyle.toLowerCamelCase(clientType.reference().name()))
+                .setType(clientType)
+                .build());
+
+    List<Statement> bodyStatements = new ArrayList<>();
+
+    RegionTag regionTag =
+        RegionTag.builder()
+            .setServiceName(clientVarExpr.variable().identifier().name())
+            .setRpcName("emtpy")
+            .build();
+
+    List<Statement> body =
+        Arrays.asList(
+            TryCatchStatement.builder()
+                .setTryResourceExpr(
+                    SampleComposerUtil.assignClientVariableWithCreateMethodExpr(clientVarExpr))
+                .setTryBody(bodyStatements)
+                .setIsSampleCode(true)
+                .build());
+    return Sample.builder().setBody(body).setRegionTag(regionTag).setIsCanonical(true).build();
+  }
+
   public static Sample composeCanonicalSample(
       Method method,
       TypeNode clientType,

src/main/java/com/google/api/generator/gapic/utils/JavaStyle.java

@@ -14,6 +14,7 @@
 
 package com.google.api.generator.gapic.utils;
 
+import com.google.api.generator.engine.lexicon.Keyword;
 import com.google.common.base.CaseFormat;
 import com.google.common.base.Strings;
 import java.util.stream.IntStream;
@@ -32,8 +33,13 @@ public static String toLowerCamelCase(String s) {
       s = CaseFormat.LOWER_UNDERSCORE.to(CaseFormat.UPPER_CAMEL, s);
     }
 
-    return capitalizeLettersAfterDigits(
-        String.format("%s%s", s.substring(0, 1).toLowerCase(), s.substring(1)));
+    String name =
+        capitalizeLettersAfterDigits(
+            String.format("%s%s", s.substring(0, 1).toLowerCase(), s.substring(1)));
+
+    // Some APIs use legit java keywords as method names. Both protobuf and gGRPC add an underscore
+    // in generated stubs to resolve name conflict, so we need to do the same.
+    return Keyword.isKeyword(name) ? name + '_' : name;
   }
 
   public static String toUpperCamelCase(String s) {

src/test/java/com/google/api/generator/gapic/composer/grpcrest/ServiceClientClassComposerTest.java

@@ -37,4 +37,17 @@ public void generateServiceClasses() {
     Path goldenFilePath = Paths.get(Utils.getGoldenDir(this.getClass()), "EchoClient.golden");
     Assert.assertCodeEquals(goldenFilePath, visitor.write());
   }
+
+  @Test
+  public void generateServiceClassesEmpty() {
+    GapicContext context = GrpcRestTestProtoLoader.instance().parseShowcaseEcho();
+    Service echoProtoService = context.services().get(1);
+    GapicClass clazz = ServiceClientClassComposer.instance().generate(context, echoProtoService);
+
+    JavaWriterVisitor visitor = new JavaWriterVisitor();
+    clazz.classDefinition().accept(visitor);
+    Utils.saveCodegenToFile(this.getClass(), "EchoEmpty.golden", visitor.write());
+    Path goldenFilePath = Paths.get(Utils.getGoldenDir(this.getClass()), "EchoEmpty.golden");
+    Assert.assertCodeEquals(goldenFilePath, visitor.write());
+  }
 }

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

@@ -0,0 +1,167 @@
+package com.google.showcase.grpcrest.v1beta1;
+
+import com.google.api.core.BetaApi;
+import com.google.api.gax.core.BackgroundResource;
+import com.google.showcase.grpcrest.v1beta1.stub.EchoEmpyStub;
+import com.google.showcase.grpcrest.v1beta1.stub.EchoEmpyStubSettings;
+import java.io.IOException;
+import java.util.concurrent.TimeUnit;
+import javax.annotation.Generated;
+
+// AUTO-GENERATED DOCUMENTATION AND CLASS.
+/**
+ * This class provides the ability to make remote calls to the backing service through method calls
+ * that map to API methods. Sample code to get started:
+ *
+ * <pre>{@code
+ * // This snippet has been automatically generated for illustrative purposes only.
+ * // It may require modifications to work in your environment.
+ * try (EchoEmpyClient echoEmpyClient = EchoEmpyClient.create()) {}
+ * }</pre>
+ *
+ * <p>Note: close() needs to be called on the EchoEmpyClient object to clean up resources such as
+ * threads. In the example above, try-with-resources is used, which automatically calls close().
+ *
+ * <p>The surface of this class includes several types of Java methods for each of the API's
+ * methods:
+ *
+ * <ol>
+ *   <li>A "flattened" method. With this type of method, the fields of the request type have been
+ *       converted into function parameters. It may be the case that not all fields are available as
+ *       parameters, and not every API method will have a flattened method entry point.
+ *   <li>A "request object" method. This type of method only takes one parameter, a request object,
+ *       which must be constructed before the call. Not every API method will have a request object
+ *       method.
+ *   <li>A "callable" method. This type of method takes no parameters and returns an immutable API
+ *       callable object, which can be used to initiate calls to the service.
+ * </ol>
+ *
+ * <p>See the individual methods for example code.
+ *
+ * <p>Many parameters require resource names to be formatted in a particular way. To assist with
+ * these names, this class includes a format method for each type of name, and additionally a parse
+ * method to extract the individual identifiers contained within names that are returned.
+ *
+ * <p>This class can be customized by passing in a custom instance of EchoEmpySettings to create().
+ * For example:
+ *
+ * <p>To customize credentials:
+ *
+ * <pre>{@code
+ * // This snippet has been automatically generated for illustrative purposes only.
+ * // It may require modifications to work in your environment.
+ * EchoEmpySettings echoEmpySettings =
+ *     EchoEmpySettings.newBuilder()
+ *         .setCredentialsProvider(FixedCredentialsProvider.create(myCredentials))
+ *         .build();
+ * EchoEmpyClient echoEmpyClient = EchoEmpyClient.create(echoEmpySettings);
+ * }</pre>
+ *
+ * <p>To customize the endpoint:
+ *
+ * <pre>{@code
+ * // This snippet has been automatically generated for illustrative purposes only.
+ * // It may require modifications to work in your environment.
+ * EchoEmpySettings echoEmpySettings =
+ *     EchoEmpySettings.newBuilder().setEndpoint(myEndpoint).build();
+ * EchoEmpyClient echoEmpyClient = EchoEmpyClient.create(echoEmpySettings);
+ * }</pre>
+ *
+ * <p>To use REST (HTTP1.1/JSON) transport (instead of gRPC) for sending an receiving requests over
+ * the wire:
+ *
+ * <pre>{@code
+ * // This snippet has been automatically generated for illustrative purposes only.
+ * // It may require modifications to work in your environment.
+ * EchoEmpySettings echoEmpySettings =
+ *     EchoEmpySettings.newBuilder()
+ *         .setTransportChannelProvider(
+ *             EchoEmpySettings.defaultHttpJsonTransportProviderBuilder().build())
+ *         .build();
+ * EchoEmpyClient echoEmpyClient = EchoEmpyClient.create(echoEmpySettings);
+ * }</pre>
+ *
+ * <p>Please refer to the GitHub repository's samples for more quickstart code snippets.
+ */
+@BetaApi
+@Generated("by gapic-generator-java")
+public class EchoEmpyClient implements BackgroundResource {
+  private final EchoEmpySettings settings;
+  private final EchoEmpyStub stub;
+
+  /** Constructs an instance of EchoEmpyClient with default settings. */
+  public static final EchoEmpyClient create() throws IOException {
+    return create(EchoEmpySettings.newBuilder().build());
+  }
+
+  /**
+   * Constructs an instance of EchoEmpyClient, using the given settings. The channels are created
+   * based on the settings passed in, or defaults for any settings that are not set.
+   */
+  public static final EchoEmpyClient create(EchoEmpySettings settings) throws IOException {
+    return new EchoEmpyClient(settings);
+  }
+
+  /**
+   * Constructs an instance of EchoEmpyClient, using the given stub for making calls. This is for
+   * advanced usage - prefer using create(EchoEmpySettings).
+   */
+  @BetaApi("A restructuring of stub classes is planned, so this may break in the future")
+  public static final EchoEmpyClient create(EchoEmpyStub stub) {
+    return new EchoEmpyClient(stub);
+  }
+
+  /**
+   * Constructs an instance of EchoEmpyClient, using the given settings. This is protected so that
+   * it is easy to make a subclass, but otherwise, the static factory methods should be preferred.
+   */
+  protected EchoEmpyClient(EchoEmpySettings settings) throws IOException {
+    this.settings = settings;
+    this.stub = ((EchoEmpyStubSettings) settings.getStubSettings()).createStub();
+  }
+
+  @BetaApi("A restructuring of stub classes is planned, so this may break in the future")
+  protected EchoEmpyClient(EchoEmpyStub stub) {
+    this.settings = null;
+    this.stub = stub;
+  }
+
+  public final EchoEmpySettings getSettings() {
+    return settings;
+  }
+
+  @BetaApi("A restructuring of stub classes is planned, so this may break in the future")
+  public EchoEmpyStub getStub() {
+    return stub;
+  }
+
+  @Override
+  public final void close() {
+    stub.close();
+  }
+
+  @Override
+  public void shutdown() {
+    stub.shutdown();
+  }
+
+  @Override
+  public boolean isShutdown() {
+    return stub.isShutdown();
+  }
+
+  @Override
+  public boolean isTerminated() {
+    return stub.isTerminated();
+  }
+
+  @Override
+  public void shutdownNow() {
+    stub.shutdownNow();
+  }
+
+  @Override
+  public boolean awaitTermination(long duration, TimeUnit unit) throws InterruptedException {
+    return stub.awaitTermination(duration, unit);
+  }
+}

src/test/java/com/google/api/generator/gapic/utils/JavaStyleTest.java

@@ -111,4 +111,14 @@ public void acronyms() {
     assertEquals("iamHttpXmlDog", JavaStyle.toLowerCamelCase(value));
     assertEquals("IamHttpXmlDog", JavaStyle.toUpperCamelCase(value));
   }
+
+  @Test
+  public void keyword() {
+    String value = "import";
+    assertEquals("import_", JavaStyle.toLowerCamelCase(value));
+    assertEquals("Import", JavaStyle.toUpperCamelCase(value));
+    value = "IMPORT_";
+    assertEquals("import_", JavaStyle.toLowerCamelCase(value));
+    assertEquals("Import", JavaStyle.toUpperCamelCase(value));
+  }
 }

src/test/proto/echo_grpcrest.proto

@@ -122,6 +122,11 @@ service Echo {
   }
 }
 
+// Generator should not fail when encounter a service without methods
+service EchoEmpy {
+  option (google.api.default_host) = "localhost:7469";
+}
+
 // A severity enum used to test enum capabilities in GAPIC surfaces
 enum Severity {
   UNNECESSARY = 0;