Implemente LRO Operation Callable Method sample code

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

@@ -489,7 +489,8 @@ private static List<MethodDefinition> createServiceMethods(
             createMethodDefaultMethod(method, clientName, messageTypes, types, resourceNames));
       }
       if (method.hasLro()) {
-        javaMethods.add(createLroCallableMethod(service, method, types));
+        javaMethods.add(
+            createLroCallableMethod(service, method, types, messageTypes, resourceNames));
       }
       if (method.isPaged()) {
         javaMethods.add(createPagedCallableMethod(service, method, types));
@@ -669,25 +670,44 @@ private static MethodDefinition createMethodDefaultMethod(
   }
 
   private static MethodDefinition createLroCallableMethod(
-      Service service, Method method, Map<String, TypeNode> types) {
-    return createCallableMethod(service, method, types, CallableMethodKind.LRO);
+      Service service,
+      Method method,
+      Map<String, TypeNode> types,
+      Map<String, Message> messageTypes,
+      Map<String, ResourceName> resourceNames) {
+    return createCallableMethod(
+        service, method, CallableMethodKind.LRO, types, messageTypes, resourceNames);
   }
 
   private static MethodDefinition createCallableMethod(
       Service service, Method method, Map<String, TypeNode> types) {
-    return createCallableMethod(service, method, types, CallableMethodKind.REGULAR);
+    return createCallableMethod(
+        service,
+        method,
+        CallableMethodKind.REGULAR,
+        types,
+        Collections.emptyMap(),
+        Collections.emptyMap());
   }
 
   private static MethodDefinition createPagedCallableMethod(
       Service service, Method method, Map<String, TypeNode> types) {
-    return createCallableMethod(service, method, types, CallableMethodKind.PAGED);
+    return createCallableMethod(
+        service,
+        method,
+        CallableMethodKind.PAGED,
+        types,
+        Collections.emptyMap(),
+        Collections.emptyMap());
   }
 
   private static MethodDefinition createCallableMethod(
       Service service,
       Method method,
+      CallableMethodKind callableMethodKind,
       Map<String, TypeNode> types,
-      CallableMethodKind callableMethodKind) {
+      Map<String, Message> messageTypes,
+      Map<String, ResourceName> resourceNames) {
     TypeNode rawCallableReturnType = null;
     if (callableMethodKind.equals(CallableMethodKind.LRO)) {
       rawCallableReturnType = types.get("OperationCallable");
@@ -729,9 +749,19 @@ private static MethodDefinition createCallableMethod(
             .setReturnType(returnType)
             .build();
 
+    Optional<String> sampleCode = Optional.empty();
+    // TODO (summerji): Implement sample code for CallableMethodKind.PAGED and
+    // CallableMethodKind.REGULAR
+    if (callableMethodKind.equals(CallableMethodKind.LRO)) {
+      sampleCode =
+          Optional.of(
+              ServiceClientSampleCodeComposer.composeRpcLroCallableMethodHeaderSampleCode(
+                  method, types.get(getClientClassName(service)), resourceNames, messageTypes));
+    }
+
     return MethodDefinition.builder()
         .setHeaderCommentStatements(
-            ServiceClientCommentComposer.createRpcCallableMethodHeaderComment(method))
+            ServiceClientCommentComposer.createRpcCallableMethodHeaderComment(method, sampleCode))
         .setScope(ScopeNode.PUBLIC)
         .setIsFinal(true)
         .setName(methodName)

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

@@ -216,7 +216,8 @@ static CommentStatement createMethodSettingsArgComment(String serviceName) {
     return toSimpleComment(String.format(CREATE_METHOD_SETTINGS_ARG_PATTERN, serviceName));
   }
 
-  static List<CommentStatement> createRpcCallableMethodHeaderComment(Method method) {
+  static List<CommentStatement> createRpcCallableMethodHeaderComment(
+      Method method, Optional<String> sampleCode) {
     JavaDocComment.Builder methodJavadocBuilder = JavaDocComment.builder();
 
     if (method.hasDescription()) {
@@ -225,7 +226,9 @@ static List<CommentStatement> createRpcCallableMethodHeaderComment(Method method
     }
 
     methodJavadocBuilder.addParagraph(METHOD_DESCRIPTION_SAMPLE_CODE_SUMMARY_STRING);
-    // TODO(summerji): Add sample code here.
+    if (sampleCode.isPresent()) {
+      methodJavadocBuilder.addSampleCode(sampleCode.get());
+    }
 
     return Arrays.asList(
         CommentComposer.AUTO_GENERATED_METHOD_COMMENT,

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

@@ -15,6 +15,7 @@
 package com.google.api.generator.gapic.composer;
 
 import com.google.api.gax.core.FixedCredentialsProvider;
+import com.google.api.gax.longrunning.OperationFuture;
 import com.google.api.generator.engine.ast.AssignmentExpr;
 import com.google.api.generator.engine.ast.CommentStatement;
 import com.google.api.generator.engine.ast.ConcreteReference;
@@ -332,6 +333,101 @@ public static String composeRpcDefaultMethodHeaderSampleCode(
             .build());
   }
 
+  public static String composeRpcLroCallableMethodHeaderSampleCode(
+      Method method,
+      TypeNode clientType,
+      Map<String, ResourceName> resourceNames,
+      Map<String, Message> messageTypes) {
+    VariableExpr clientVarExpr =
+        VariableExpr.withVariable(
+            Variable.builder()
+                .setName(JavaStyle.toLowerCamelCase(clientType.reference().name()))
+                .setType(clientType)
+                .build());
+    // Assign method's request variable with the default value.
+    VariableExpr requestVarExpr =
+        VariableExpr.withVariable(
+            Variable.builder().setName("request").setType(method.inputType()).build());
+    Message requestMessage = messageTypes.get(method.inputType().reference().simpleName());
+    Preconditions.checkNotNull(requestMessage);
+    Expr requestBuilderExpr =
+        DefaultValueComposer.createSimpleMessageBuilderExpr(
+            requestMessage, resourceNames, messageTypes);
+    List<Expr> bodyExprs = new ArrayList<>();
+    bodyExprs.add(
+        AssignmentExpr.builder()
+            .setVariableExpr(requestVarExpr.toBuilder().setIsDecl(true).build())
+            .setValueExpr(requestBuilderExpr)
+            .build());
+    TypeNode operationFutureType =
+        TypeNode.withReference(
+            ConcreteReference.builder()
+                .setClazz(OperationFuture.class)
+                .setGenerics(
+                    method.lro().responseType().reference(),
+                    method.lro().metadataType().reference())
+                .build());
+    VariableExpr operationFutureVarExpr =
+        VariableExpr.withVariable(
+            Variable.builder().setName("future").setType(operationFutureType).build());
+    MethodInvocationExpr rpcMethodInvocationExpr =
+        MethodInvocationExpr.builder()
+            .setExprReferenceExpr(clientVarExpr)
+            .setMethodName(
+                String.format("%sOperationCallable", JavaStyle.toLowerCamelCase(method.name())))
+            .build();
+    rpcMethodInvocationExpr =
+        MethodInvocationExpr.builder()
+            .setExprReferenceExpr(rpcMethodInvocationExpr)
+            .setMethodName("futureCall")
+            .setArguments(requestVarExpr)
+            .setReturnType(operationFutureType)
+            .build();
+    bodyExprs.add(
+        AssignmentExpr.builder()
+            .setVariableExpr(operationFutureVarExpr.toBuilder().setIsDecl(true).build())
+            .setValueExpr(rpcMethodInvocationExpr)
+            .build());
+    List<Statement> bodyStatements =
+        bodyExprs.stream().map(e -> ExprStatement.withExpr(e)).collect(Collectors.toList());
+    bodyExprs.clear();
+    bodyStatements.add(CommentStatement.withComment(LineComment.withComment("Do something;")));
+    MethodInvocationExpr futureGetMethodExpr =
+        MethodInvocationExpr.builder()
+            .setExprReferenceExpr(operationFutureVarExpr)
+            .setMethodName("get")
+            .setReturnType(method.lro().responseType())
+            .build();
+    boolean returnVoid = isProtoEmptyType(method.lro().responseType());
+    if (returnVoid) {
+      bodyExprs.add(futureGetMethodExpr);
+    } else {
+      VariableExpr responseVarExpr =
+          VariableExpr.builder()
+              .setVariable(
+                  Variable.builder()
+                      .setName("response")
+                      .setType(method.lro().responseType())
+                      .build())
+              .setIsDecl(true)
+              .build();
+      bodyExprs.add(
+          AssignmentExpr.builder()
+              .setVariableExpr(responseVarExpr)
+              .setValueExpr(futureGetMethodExpr)
+              .build());
+    }
+    bodyStatements.addAll(
+        bodyExprs.stream().map(e -> ExprStatement.withExpr(e)).collect(Collectors.toList()));
+    bodyExprs.clear();
+    return SampleCodeWriter.write(
+        TryCatchStatement.builder()
+            .setTryResourceExpr(assignClientVariableWithCreateMethodExpr(clientVarExpr))
+            .setTryBody(bodyStatements)
+            .setIsSampleCode(true)
+            .build());
+  }
+
   @VisibleForTesting
   static TryCatchStatement composeUnaryRpcMethodSampleCode(
       Method method,

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

@@ -504,7 +504,19 @@ public class EchoClient implements BackgroundResource {
   }
 
   // AUTO-GENERATED DOCUMENTATION AND METHOD.
-  /** Sample code: */
+  /**
+   * Sample code:
+   *
+   * <pre>{@code
+   * try (EchoClient echoClient = EchoClient.create()) {
+   *   WaitRequest request = WaitRequest.newBuilder().build();
+   *   OperationFuture<WaitResponse, WaitMetadata> future =
+   *       echoClient.waitOperationCallable().futureCall(request);
+   *   // Do something;
+   *   WaitResponse response = future.get();
+   * }
+   * }</pre>
+   */
   public final OperationCallable<WaitRequest, WaitResponse, WaitMetadata> waitOperationCallable() {
     return stub.waitOperationCallable();
   }

test/integration/goldens/asset/AssetServiceClient.java

@@ -202,6 +202,22 @@ public final OperationFuture<ExportAssetsResponse, ExportAssetsRequest> exportAs
    * export operation usually finishes within 5 minutes.
    *
    * <p>Sample code:
+   *
+   * <pre>{@code
+   * try (AssetServiceClient assetServiceClient = AssetServiceClient.create()) {
+   *   ExportAssetsRequest request =
+   *       ExportAssetsRequest.newBuilder()
+   *           .setParent(FeedName.ofProjectFeedName("[PROJECT]", "[FEED]").toString())
+   *           .setReadTime(Timestamp.newBuilder().build())
+   *           .addAllAssetTypes(new ArrayList<String>())
+   *           .setOutputConfig(OutputConfig.newBuilder().build())
+   *           .build();
+   *   OperationFuture<ExportAssetsResponse, ExportAssetsRequest> future =
+   *       assetServiceClient.exportAssetsOperationCallable().futureCall(request);
+   *   // Do something;
+   *   ExportAssetsResponse response = future.get();
+   * }
+   * }</pre>
    */
   public final OperationCallable<ExportAssetsRequest, ExportAssetsResponse, ExportAssetsRequest>
       exportAssetsOperationCallable() {