feat: gapic-generator-java to perform a no-op when no services are de…

…tected (#2460)

Fixes #2050

Adds behavior to gracefully perform a NOOP if no services are contained
in the generation request.


## Confimation in hermetic build scripts

From `generate_library.sh` against `google/cloud/alloydb/connectors/v1`
```
+ /usr/local/google/home/diegomarquezp/Desktop/sdk2/sdk3/sdk-platform-java/library_generation/output/protobuf-25.2/bin/protoc --experimental_allow_proto3_optional --plugin=protoc-gen-java_gapic=/usr/local/google/home/diegomarquezp/.pyenv/versions/3.11.0/lib/python3.11/site-packages/library_generation/gapic-generator-java-wrapper --java_gapic_out=metadata:/usr/local/google/home/diegomarquezp/Desktop/sdk2/sdk3/sdk-platform-java/library_generation/output/temp_preprocessed/java_gapic_srcjar_raw.srcjar.zip --java_gapic_opt=transport=grpc,rest-numeric-enums,grpc-service-config=,gapic-config=,api-service-config=google/cloud/alloydb/connectors/v1/connectors_v1.yaml google/cloud/alloydb/connectors/v1/resources.proto google/cloud/common_resources.proto
Apr 05, 2024 9:33:22 PM com.google.api.generator.gapic.protoparser.Parser parse
WARNING: No services found to generate. This will produce an empty zip file
Apr 05, 2024 9:33:22 PM com.google.api.generator.gapic.composer.ClientLibraryPackageInfoComposer generatePackageInfo
WARNING: Generating empty package info since no services were found
+ did_generate_gapic=true
+ zipinfo -t /usr/local/google/home/diegomarquezp/Desktop/sdk2/sdk3/sdk-platform-java/library_generation/output/temp_preprocessed/java_gapic_srcjar_raw.srcjar.zip
Empty zipfile. 
+ did_generate_gapic=false
+ [[ false == \t\r\u\e ]]

```

I made some changes to library_generation but I moved them to a follow
up PR (#2599) so the
checks can pass here.

gapic-generator-java/src/main/java/com/google/api/generator/Main.java

@@ -14,6 +14,8 @@
 
 package com.google.api.generator;
 
+import static com.google.api.generator.gapic.protowriter.Writer.EMPTY_RESPONSE;
+
 import com.google.api.generator.gapic.Generator;
 import com.google.protobuf.ExtensionRegistry;
 import com.google.protobuf.compiler.PluginProtos.CodeGeneratorRequest;
@@ -26,6 +28,8 @@ public static void main(String[] args) throws IOException {
  ProtoRegistry.registerAllExtensions(registry);
  CodeGeneratorRequest request = CodeGeneratorRequest.parseFrom(System.in, registry);
  CodeGeneratorResponse response = Generator.generateGapic(request);
- response.writeTo(System.out);
+ if (response != EMPTY_RESPONSE) {
+ response.writeTo(System.out);
+ }
  }
 }

gapic-generator-java/src/main/java/com/google/api/generator/gapic/composer/ClientLibraryPackageInfoComposer.java

@@ -29,11 +29,15 @@
 import com.google.api.generator.gapic.model.GapicPackageInfo;
 import com.google.api.generator.gapic.model.Sample;
 import com.google.api.generator.gapic.model.Service;
-import com.google.common.base.Preconditions;
 import com.google.common.base.Strings;
+import java.util.logging.Logger;
 import javax.annotation.Generated;
 
 public class ClientLibraryPackageInfoComposer {
+
+ private static final Logger LOGGER =
+ Logger.getLogger(ClientLibraryPackageInfoComposer.class.getName());
+
  private static final String DIVIDER = "=======================";
 
  private static final String PACKAGE_INFO_DESCRIPTION =
@@ -44,7 +48,10 @@ public class ClientLibraryPackageInfoComposer {
  private static final String SERVICE_DESCRIPTION_HEADER_PATTERN = "Service Description: %s";
 
  public static GapicPackageInfo generatePackageInfo(GapicContext context) {
- Preconditions.checkState(!context.services().isEmpty(), "No services found to generate");
+ if (!context.containsServices()) {
+ LOGGER.warning("Generating empty package info since no services were found");
+ return null;
+ }
  // Pick some service's package, as we assume they are all the same.
  String libraryPakkage = context.services().get(0).pakkage();
 

gapic-generator-java/src/main/java/com/google/api/generator/gapic/composer/Composer.java

@@ -53,6 +53,9 @@ public static List<GapicClass> composeServiceClasses(GapicContext context) {
  }
 
  public static GapicPackageInfo composePackageInfo(GapicContext context) {
+ if (!context.containsServices()) {
+ return null;
+ }
  return addApacheLicense(ClientLibraryPackageInfoComposer.generatePackageInfo(context));
  }
 

gapic-generator-java/src/main/java/com/google/api/generator/gapic/model/GapicContext.java

@@ -21,6 +21,7 @@
 import java.util.Collections;
 import java.util.List;
 import java.util.Map;
+import java.util.Optional;
 import java.util.Set;
 import java.util.TreeMap;
 import java.util.stream.Collectors;
@@ -32,6 +33,16 @@ public abstract class GapicContext {
  // it iteratively as we generate client methods.
  private GapicMetadata gapicMetadata = defaultGapicMetadata();
 
+ public static final GapicContext EMPTY =
+ builder()
+ .setServices(Collections.emptyList())
+ .setMessages(Collections.emptyMap())
+ .setServiceConfig(GapicServiceConfig.create(Optional.empty()))
+ .setResourceNames(Collections.emptyMap())
+ .setHelperResourceNames(Collections.emptySet())
+ .setTransport(Transport.GRPC)
+ .build();
+
  // Maps the message name (as it appears in the protobuf) to Messages.
  public abstract ImmutableMap<String, Message> messages();
 
@@ -59,6 +70,10 @@ public GapicMetadata gapicMetadata() {
  @Nullable
  public abstract com.google.api.Service serviceYamlProto();
 
+ public boolean containsServices() {
+ return !services().isEmpty();
+ }
+
  public boolean hasServiceYamlProto() {
  return serviceYamlProto() != null;
  }

gapic-generator-java/src/main/java/com/google/api/generator/gapic/protoparser/Parser.java

@@ -79,14 +79,18 @@
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
+import java.util.Map.Entry;
 import java.util.Objects;
 import java.util.Optional;
 import java.util.Set;
 import java.util.function.Function;
+import java.util.logging.Logger;
 import java.util.stream.Collectors;
 import java.util.stream.IntStream;
 
 public class Parser {
+
+ private static final Logger LOGGER = Logger.getLogger(Parser.class.getName());
  private static final String COMMA = ",";
  private static final String COLON = ":";
  private static final String DEFAULT_PORT = "443";
@@ -175,7 +179,10 @@ public static GapicContext parse(CodeGeneratorRequest request) {
  mixinServices,
  transport);
 
- Preconditions.checkState(!services.isEmpty(), "No services found to generate");
+ if (services.isEmpty()) {
+ LOGGER.warning("No services found to generate. This will cause a no-op (no files generated)");
+ return GapicContext.EMPTY;
+ }
 
  // TODO(vam-google): Figure out whether we should keep this allowlist or bring
  // back the unused resource names for all APIs.
@@ -1102,7 +1109,8 @@ private static Map<String, FileDescriptor> getFilesToGenerate(CodeGeneratorReque
  return fileDescriptors;
  }
 
- private static String parseServiceJavaPackage(CodeGeneratorRequest request) {
+ @VisibleForTesting
+ static String parseServiceJavaPackage(CodeGeneratorRequest request) {
  Map<String, Integer> javaPackageCount = new HashMap<>();
  Map<String, FileDescriptor> fileDescriptors = getFilesToGenerate(request);
  for (String fileToGenerate : request.getFileToGenerateList()) {
@@ -1135,13 +1143,12 @@ private static String parseServiceJavaPackage(CodeGeneratorRequest request) {
  processedJavaPackageCount = javaPackageCount;
  }
 
- String finalJavaPackage =
- processedJavaPackageCount.entrySet().stream()
- .max(Map.Entry.comparingByValue())
- .get()
- .getKey();
- Preconditions.checkState(
- !Strings.isNullOrEmpty(finalJavaPackage), "No service Java package found");
+ String finalJavaPackage = "";
+ Optional<Entry<String, Integer>> finalPackageEntry =
+ processedJavaPackageCount.entrySet().stream().max(Map.Entry.comparingByValue());
+ if (finalPackageEntry.isPresent()) {
+ finalJavaPackage = finalPackageEntry.get().getKey();
+ }
  return finalJavaPackage;
  }
 

gapic-generator-java/src/main/java/com/google/api/generator/gapic/protowriter/Writer.java

@@ -36,29 +36,29 @@
 import java.util.jar.JarOutputStream;
 
 public class Writer {
- static class GapicWriterException extends RuntimeException {
- public GapicWriterException(String errorMessage) {
- super(errorMessage);
- }
 
+ static class GapicWriterException extends RuntimeException {
  public GapicWriterException(String errorMessage, Throwable cause) {
  super(errorMessage, cause);
  }
  }
 
- public static CodeGeneratorResponse write(
+ public static final CodeGeneratorResponse EMPTY_RESPONSE = null;
+
+ @VisibleForTesting
+ protected static CodeGeneratorResponse write(
  GapicContext context,
  List<GapicClass> clazzes,
  GapicPackageInfo gapicPackageInfo,
  List<ReflectConfig> reflectConfigInfo,
- String outputFilePath) {
- ByteString.Output output = ByteString.newOutput();
+ String outputFilePath,
+ JarOutputStream jos,
+ ByteString.Output output)
+ throws IOException {
  JavaWriterVisitor codeWriter = new JavaWriterVisitor();
- JarOutputStream jos;
- try {
- jos = new JarOutputStream(output);
- } catch (IOException e) {
- throw new GapicWriterException(e.getMessage(), e);
+
+ if (!context.containsServices()) {
+ return EMPTY_RESPONSE;
  }
 
  for (GapicClass gapicClazz : clazzes) {
@@ -72,12 +72,8 @@ public static CodeGeneratorResponse write(
  writeMetadataFile(context, writePackageInfo(gapicPackageInfo, codeWriter, jos), jos);
  writeReflectConfigFile(gapicPackageInfo.packageInfo().pakkage(), reflectConfigInfo, jos);
 
- try {
- jos.finish();
- jos.flush();
- } catch (IOException e) {
- throw new GapicWriterException(e.getMessage(), e);
- }
+ jos.finish();
+ jos.flush();
 
  CodeGeneratorResponse.Builder response = CodeGeneratorResponse.newBuilder();
  response
@@ -88,6 +84,23 @@ public static CodeGeneratorResponse write(
  return response.build();
  }
 
+ public static CodeGeneratorResponse write(
+ GapicContext context,
+ List<GapicClass> clazzes,
+ GapicPackageInfo gapicPackageInfo,
+ List<ReflectConfig> reflectConfigInfo,
+ String outputFilePath) {
+ ByteString.Output output = ByteString.newOutput();
+ CodeGeneratorResponse response;
+ try (JarOutputStream jos = new JarOutputStream(output)) {
+ response =
+ write(context, clazzes, gapicPackageInfo, reflectConfigInfo, outputFilePath, jos, output);
+ } catch (IOException e) {
+ throw new GapicWriterException(e.getMessage(), e);
+ }
+ return response;
+ }
+
  @VisibleForTesting
  static void writeReflectConfigFile(
  String pakkage, List<ReflectConfig> reflectConfigInfo, JarOutputStream jos) {
@@ -167,7 +180,8 @@ private static void writeSamples(
  }
  }
 
- private static String writePackageInfo(
+ @VisibleForTesting
+ static String writePackageInfo(
  GapicPackageInfo gapicPackageInfo, JavaWriterVisitor codeWriter, JarOutputStream jos) {
  PackageInfoDefinition packageInfo = gapicPackageInfo.packageInfo();
  packageInfo.accept(codeWriter);

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/ClientLibraryPackageInfoComposerTest.java

@@ -14,6 +14,8 @@
 
 package com.google.api.generator.gapic.composer;
 
+import static org.junit.jupiter.api.Assertions.assertNull;
+
 import com.google.api.generator.engine.writer.JavaWriterVisitor;
 import com.google.api.generator.gapic.model.GapicContext;
 import com.google.api.generator.gapic.model.GapicPackageInfo;
@@ -39,4 +41,9 @@ void composePackageInfo_showcase() {
  GoldenFileWriter.getGoldenDir(this.getClass()), "ShowcaseWithEchoPackageInfo.golden");
  Assert.assertCodeEquals(goldenFilePath, visitor.write());
  }
+
+ @Test
+ void testGeneratePackageInfo_noServices_returnsNullPackageInfo() {
+ assertNull(ClientLibraryPackageInfoComposer.generatePackageInfo(GapicContext.EMPTY));
+ }
 }

gapic-generator-java/src/test/java/com/google/api/generator/gapic/composer/ComposerTest.java

@@ -14,8 +14,10 @@
 
 package com.google.api.generator.gapic.composer;
 
-import static org.junit.Assert.assertEquals;
-import static org.junit.Assert.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertFalse;
+import static org.junit.jupiter.api.Assertions.assertNull;
+import static org.junit.jupiter.api.Assertions.assertTrue;
 
 import com.google.api.generator.engine.ast.ClassDefinition;
 import com.google.api.generator.engine.ast.ScopeNode;
@@ -35,6 +37,7 @@
 import java.nio.file.Paths;
 import java.util.Arrays;
 import java.util.List;
+import org.junit.jupiter.api.BeforeEach;
 import org.junit.jupiter.api.Test;
 
 class ComposerTest {
@@ -53,8 +56,13 @@ class ComposerTest {
  .build();
  private List<Sample> ListofSamples = Arrays.asList(new Sample[] {sample});
 
+ @BeforeEach
+ void initialSanityCheck() {
+ assertTrue(context.containsServices());
+ }
+
  @Test
- void gapicClass_addApacheLicense() {
+ public void gapicClass_addApacheLicense_validInput_succeeds() {
  ClassDefinition classDef =
  ClassDefinition.builder()
  .setPackageString("com.google.showcase.v1beta1.stub")
@@ -84,14 +92,14 @@ void composeSamples_showcase() {
  assertFalse(composedSamples.isEmpty());
  for (Sample sample : composedSamples) {
  assertEquals(
- "File header should be APACHE",
  Arrays.asList(CommentComposer.APACHE_LICENSE_COMMENT),
- sample.fileHeader());
+ sample.fileHeader(),
+ "File header should be APACHE");
  assertEquals(
- "ApiShortName should be Localhost7469",
  "Localhost7469",
- sample.regionTag().apiShortName());
- assertEquals("ApiVersion should be V1Beta1", "V1Beta1", sample.regionTag().apiVersion());
+ sample.regionTag().apiShortName(),
+ "ApiShortName should be Localhost7469");
+ assertEquals("V1Beta1", sample.regionTag().apiVersion(), "ApiVersion should be V1Beta1");
  }
  }
 
@@ -120,10 +128,10 @@ void composeSamples_parseProtoPackage() {
 
  for (Sample sample : composedSamples) {
  assertEquals(
- "ApiShortName should be Accessapproval",
+ "Accessapproval",
  sample.regionTag().apiShortName(),
- "Accessapproval");
- assertEquals("ApiVersion should be V1", sample.regionTag().apiVersion(), "V1");
+ "ApiShortName should be Accessapproval");
+ assertEquals("V1", sample.regionTag().apiVersion(), "ApiVersion should be V1");
  }
 
  protoPack = "google.cloud.vision.v1p1beta1";
@@ -136,8 +144,8 @@ void composeSamples_parseProtoPackage() {
  assertFalse(composedSamples.isEmpty());
 
  for (Sample sample : composedSamples) {
- assertEquals("ApiShortName should be Vision", sample.regionTag().apiShortName(), "Vision");
- assertEquals("ApiVersion should be V1P1Beta1", sample.regionTag().apiVersion(), "V1P1Beta1");
+ assertEquals("Vision", sample.regionTag().apiShortName(), "ApiShortName should be Vision");
+ assertEquals("V1P1Beta1", sample.regionTag().apiVersion(), "ApiVersion should be V1P1Beta1");
  }
 
  protoPack = "google.cloud.vision";
@@ -149,11 +157,21 @@ void composeSamples_parseProtoPackage() {
  assertFalse(composedSamples.isEmpty());
 
  for (Sample sample : composedSamples) {
- assertEquals("ApiShortName should be Vision", sample.regionTag().apiShortName(), "Vision");
- assertEquals("ApiVersion should be empty", sample.regionTag().apiVersion(), "");
+ assertEquals("Vision", sample.regionTag().apiShortName(), "ApiShortName should be Vision");
+ assertTrue(sample.regionTag().apiVersion().isEmpty(), "ApiVersion should be empty");
  }
  }
 
+ @Test
+ void testEmptyGapicContext_doesNotThrow() {
+ assertTrue(Composer.composeServiceClasses(GapicContext.EMPTY).isEmpty());
+ }
+
+ @Test
+ void testComposePackageInfo_emptyGapicContext_returnsNull() {
+ assertNull(Composer.composePackageInfo(GapicContext.EMPTY));
+ }
+
  private List<GapicClass> getTestClassListFromService(Service testService) {
  GapicClass testClass =
  GrpcServiceCallableFactoryClassComposer.instance()