[samplecode]Add package info sample code

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

@@ -20,6 +20,8 @@
 import com.google.api.generator.engine.ast.JavaDocComment;
 import com.google.api.generator.engine.ast.PackageInfoDefinition;
 import com.google.api.generator.engine.ast.TypeNode;
+import com.google.api.generator.engine.ast.VaporReference;
+import com.google.api.generator.gapic.composer.samplecode.ServiceClientSampleCodeComposer;
 import com.google.api.generator.gapic.composer.utils.ClassNames;
 import com.google.api.generator.gapic.model.GapicContext;
 import com.google.api.generator.gapic.model.GapicPackageInfo;
@@ -111,7 +113,16 @@ private static CommentStatement createPackageInfoJavadoc(GapicContext context) {
       javaDocCommentBuilder =
           javaDocCommentBuilder.addParagraph(
               String.format(SAMPLE_CODE_HEADER_PATTERN, javaClientName));
-      // TODO(summerji): Add package-info.java sample code here.
+      TypeNode clientType =
+          TypeNode.withReference(
+              VaporReference.builder()
+                  .setPakkage(service.pakkage())
+                  .setName(ClassNames.getServiceClientClassName(service))
+                  .build());
+      String packageInfoSampleCode =
+          ServiceClientSampleCodeComposer.composeClassHeaderMethodSampleCode(
+              service, clientType, context.resourceNames(), context.messages());
+      javaDocCommentBuilder.addSampleCode(packageInfoSampleCode);
     }
 
     return CommentStatement.withComment(javaDocCommentBuilder.build());

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

@@ -129,7 +129,8 @@ public GapicClass generate(
 
     ClassDefinition classDef =
         ClassDefinition.builder()
-            .setHeaderCommentStatements(createClassHeaderComments(service, typeStore))
+            .setHeaderCommentStatements(
+                createClassHeaderComments(service, typeStore, resourceNames, messageTypes))
             .setPackageString(pakkage)
             .setAnnotations(createClassAnnotations(pakkage, typeStore))
             .setScope(ScopeNode.PUBLIC)
@@ -161,17 +162,23 @@ private static List<TypeNode> createClassImplements(TypeStore typeStore) {
   }
 
   private static List<CommentStatement> createClassHeaderComments(
-      Service service, TypeStore typeStore) {
+      Service service,
+      TypeStore typeStore,
+      Map<String, ResourceName> resourceNames,
+      Map<String, Message> messageTypes) {
     TypeNode clientType = typeStore.get(ClassNames.getServiceClientClassName(service));
     TypeNode settingsType = typeStore.get(ClassNames.getServiceSettingsClassName(service));
+    String classMethodSampleCode =
+        ServiceClientSampleCodeComposer.composeClassHeaderMethodSampleCode(
+            service, clientType, resourceNames, messageTypes);
     String credentialsSampleCode =
         ServiceClientSampleCodeComposer.composeClassHeaderCredentialsSampleCode(
             clientType, settingsType);
     String endpointSampleCode =
         ServiceClientSampleCodeComposer.composeClassHeaderEndpointSampleCode(
             clientType, settingsType);
     return ServiceClientCommentComposer.createClassHeaderComments(
-        service, credentialsSampleCode, endpointSampleCode);
+        service, classMethodSampleCode, credentialsSampleCode, endpointSampleCode);
   }
 
   private static List<MethodDefinition> createClassMethods(

src/main/java/com/google/api/generator/gapic/composer/comment/ServiceClientCommentComposer.java

@@ -110,7 +110,10 @@ public class ServiceClientCommentComposer {
               + " operation returned by another API method call.");
 
   public static List<CommentStatement> createClassHeaderComments(
-      Service service, String credentialsSampleCode, String endpointSampleCode) {
+      Service service,
+      String classMethodSampleCode,
+      String credentialsSampleCode,
+      String endpointSampleCode) {
     JavaDocComment.Builder classHeaderJavadocBuilder = JavaDocComment.builder();
     if (service.hasDescription()) {
       classHeaderJavadocBuilder =
@@ -122,7 +125,7 @@ public static List<CommentStatement> createClassHeaderComments(
 
     // Service introduction.
     classHeaderJavadocBuilder.addParagraph(SERVICE_DESCRIPTION_INTRO_STRING);
-    // TODO(summerji): Add sample code here.
+    classHeaderJavadocBuilder.addSampleCode(classMethodSampleCode);
 
     // API surface description.
     classHeaderJavadocBuilder.addParagraph(

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

@@ -44,6 +44,7 @@
 import com.google.api.generator.gapic.model.Method.Stream;
 import com.google.api.generator.gapic.model.MethodArgument;
 import com.google.api.generator.gapic.model.ResourceName;
+import com.google.api.generator.gapic.model.Service;
 import com.google.api.generator.gapic.utils.JavaStyle;
 import com.google.common.base.Preconditions;
 import java.util.ArrayList;
@@ -56,8 +57,31 @@
 
 public class ServiceClientSampleCodeComposer {
 
+  public static String composeClassHeaderMethodSampleCode(
+      Service service,
+      TypeNode clientType,
+      Map<String, ResourceName> resourceNames,
+      Map<String, Message> messageTypes) {
+    // 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() == Stream.NONE && !m.hasLro() && !m.isPaged())
+            .findFirst()
+            .orElse(service.methods().get(0));
+    if (method.stream() == Stream.NONE) {
+      if (method.methodSignatures().isEmpty()) {
+        return composeRpcDefaultMethodHeaderSampleCode(
+            method, clientType, resourceNames, messageTypes);
+      }
+      return composeRpcMethodHeaderSampleCode(
+          method, clientType, method.methodSignatures().get(0), resourceNames, messageTypes);
+    }
+    return composeStreamCallableMethodHeaderSampleCode(
+        method, clientType, resourceNames, messageTypes);
+  }
+
   public static String composeClassHeaderCredentialsSampleCode(
-      // TODO(summerji): Add unit tests for composeClassHeaderCredentialsSampleCode.
       TypeNode clientType, TypeNode settingsType) {
     // Initialize clientSettings with builder() method.
     // e.g. EchoSettings echoSettings =
@@ -130,7 +154,6 @@ public static String composeClassHeaderCredentialsSampleCode(
   }
 
   public static String composeClassHeaderEndpointSampleCode(
-      // TODO(summerji): Add unit tests for composeClassHeaderEndpointSampleCode.
       TypeNode clientType, TypeNode settingsType) {
     // Initialize client settings with builder() method.
     // e.g. EchoSettings echoSettings = EchoSettings.newBuilder().setEndpoint("myEndpoint").build();

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

@@ -34,6 +34,12 @@ import javax.annotation.Generated;
  * 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
+ * try (EchoClient echoClient = EchoClient.create()) {
+ *   EchoResponse response = echoClient.echo();
+ * }
+ * }</pre>
+ *
  * <p>Note: close() needs to be called on the EchoClient object to clean up resources such as
  * threads. In the example above, try-with-resources is used, which automatically calls close().
  *

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

@@ -24,6 +24,15 @@ import javax.annotation.Generated;
  * 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
+ * try (IdentityClient identityClient = IdentityClient.create()) {
+ *   String parent = UserName.of("[USER]").toString();
+ *   String displayName = "displayName1714148973";
+ *   String email = "email96619420";
+ *   User response = identityClient.createUser(parent, displayName, email);
+ * }
+ * }</pre>
+ *
  * <p>Note: close() needs to be called on the IdentityClient object to clean up resources such as
  * threads. In the example above, try-with-resources is used, which automatically calls close().
  *