Add lang to aidl step

Summary:
Looking to add ndk support for native binder. This can be done with the `--lang=` from the aidl tool. The first step is to add this flag without changing existing behaviour.

https://source.android.com/devices/architecture/aidl/aidl-backends

Reviewed By: vener91

fbshipit-source-id: c923180a9b2b1d6c2091b6fb5b50bb483bebc17c

Author: Allison Chan

src/com/facebook/buck/android/AidlBackend.java

@@ -0,0 +1,22 @@
+/*
+ * Copyright (c) Facebook, Inc. and its affiliates.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.facebook.buck.android;
+
+enum AidlBackend {
+  java,
+  ndk
+}

src/com/facebook/buck/android/AidlStep.java

@@ -40,6 +40,7 @@ public class AidlStep extends IsolatedShellStep {
   private final Path aidlFilePath;
   private final Set<String> importDirectoryPaths;
   private final Path destinationDirectory;
+  private final AidlBackend backend;
 
   public AidlStep(
       ProjectFilesystem filesystem,
@@ -49,7 +50,8 @@ public AidlStep(
       Set<String> importDirectoryPaths,
       Path destinationDirectory,
       RelPath cellPath,
-      boolean withDownwardApi) {
+      boolean withDownwardApi,
+      AidlBackend backend) {
     super(filesystem.getRootPath(), cellPath, withDownwardApi);
 
     this.filesystem = filesystem;
@@ -58,6 +60,7 @@ public AidlStep(
     this.aidlFilePath = aidlFilePath;
     this.importDirectoryPaths = ImmutableSet.copyOf(importDirectoryPaths);
     this.destinationDirectory = destinationDirectory;
+    this.backend = backend;
   }
 
   @Override
@@ -82,6 +85,9 @@ protected ImmutableList<String> getShellCommandInternal(IsolatedExecutionContext
     // file created by --preprocess to import
     args.add("-p" + androidPlatformTarget.getAndroidFrameworkIdlFile());
 
+    // target language
+    args.add("--lang=" + backend.name());
+
     // search path for import statements
     for (String importDirectoryPath : importDirectoryPaths) {
       Path resolved = filesystem.getPathForRelativePath(Paths.get(importDirectoryPath));

src/com/facebook/buck/android/GenAidl.java

@@ -132,7 +132,8 @@ public ImmutableList<Step> getBuildSteps(
             outputDirectory.getPath(),
             ProjectFilesystemUtils.relativize(
                 getProjectFilesystem().getRootPath(), context.getBuildCellRootPath()),
-            withDownwardApi);
+            withDownwardApi,
+            AidlBackend.java);
     commands.add(command);
 
     // Files must ultimately be written to GEN_DIR to be used as source paths.

test/com/facebook/buck/android/GenAidlTest.java

@@ -73,6 +73,7 @@ public class GenAidlTest {
   private String pathToFrameworkAidl;
   private String importPath;
   private AndroidPlatformTarget androidPlatformTarget;
+  private AidlBackend backend;
 
   @Before
   public void setUp() throws IOException {
@@ -104,6 +105,7 @@ public void setUp() throws IOException {
 
     target = BuildTargetFactory.newInstance("//java/com/example/base:IWhateverService");
     pathResolver = new TestActionGraphBuilder().getSourcePathResolver();
+    backend = AidlBackend.java;
   }
 
   private GenAidl createGenAidlRule(ImmutableSortedSet<SourcePath> aidlSourceDeps) {
@@ -152,14 +154,15 @@ public void testSimpleGenAidlRule() {
     assertEquals(
         "gen_aidl() should use the aidl binary to write .java files.",
         String.format(
-            "(cd %s && %s -p%s -I%s -o%s %s)",
+            "(cd %s && %s -p%s --lang=%s -I%s -o%s %s)",
             stubFilesystem.getRootPath(),
             pathToAidlExecutable,
             pathToFrameworkAidl,
+            backend.name(),
             stubFilesystem.resolve(importPath),
             stubFilesystem.resolve(outputDirectory),
             pathToAidl.getRelativePath()),
-        aidlStep.getDescription(TestExecutionContext.newBuilder().build()));
+        aidlStep.getDescription(TestExecutionContext.newBuilder().build()).replace("'", ""));
 
     assertEquals(7, steps.size());
   }