Put generated kernel files into <build> folder (#14693)

* Put generated kernel files into <build> directory

* USe default value for kernel file

packages/flutter_tools/lib/src/commands/build_aot.dart

@@ -282,6 +282,7 @@ Future<String> _buildAotSnapshot(
   final String kIsolateSnapshotDataC = fs.path.join(outputDir.path, '$kIsolateSnapshotData.c');
   final String kVmSnapshotDataO = fs.path.join(outputDir.path, '$kVmSnapshotData.o');
   final String kIsolateSnapshotDataO = fs.path.join(outputDir.path, '$kIsolateSnapshotData.o');
+  final String kApplicationKernelPath = fs.path.join(getBuildDirectory(), 'app.dill');
 
   switch (platform) {
     case TargetPlatform.android_arm:
@@ -338,6 +339,7 @@ Future<String> _buildAotSnapshot(
     mainPath = await compile(
       sdkRoot: artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath),
       mainPath: mainPath,
+      outputFilePath: kApplicationKernelPath,
       extraFrontEndOptions: extraFrontEndOptions,
       linkPlatformKernelIn : true,
       aot : true,

packages/flutter_tools/lib/src/commands/build_flx.dart

@@ -20,6 +20,7 @@ class BuildFlxCommand extends BuildSubCommand {
     argParser.addOption('output-file', abbr: 'o', defaultsTo: defaultFlxOutputPath);
     argParser.addOption('snapshot', defaultsTo: defaultSnapshotPath);
     argParser.addOption('depfile', defaultsTo: defaultDepfilePath);
+    argParser.addOption('kernel-file', defaultsTo: defaultApplicationKernelPath);
     argParser.addFlag('preview-dart-2', negatable: false, hide: !verboseHelp);
     argParser.addFlag(
       'track-widget-creation',
@@ -51,6 +52,7 @@ class BuildFlxCommand extends BuildSubCommand {
       manifestPath: argResults['manifest'],
       outputPath: outputPath,
       snapshotPath: argResults['snapshot'],
+      applicationKernelFilePath: argResults['kernel-file'],
       depfilePath: argResults['depfile'],
       privateKeyPath: argResults['private-key'],
       workingDirPath: argResults['working-dir'],

packages/flutter_tools/lib/src/compile.dart

@@ -58,6 +58,7 @@ class _StdoutHandler {
 Future<String> compile(
     {String sdkRoot,
     String mainPath,
+    String outputFilePath,
     bool linkPlatformKernelIn: false,
     bool aot: false,
     bool trackWidgetCreation: false,
@@ -91,6 +92,9 @@ Future<String> compile(
   if (packagesPath != null) {
     command.addAll(<String>['--packages', packagesPath]);
   }
+  if (outputFilePath != null) {
+    command.addAll(<String>['--output-dill', outputFilePath]);
+  }
 
   if (extraFrontEndOptions != null)
     command.addAll(extraFrontEndOptions);
@@ -140,13 +144,14 @@ class ResidentCompiler {
   /// into new binary.
   /// Binary file name is returned if compilation was successful, otherwise
   /// null is returned.
-  Future<String> recompile(String mainPath, List<String> invalidatedFiles) async {
+  Future<String> recompile(String mainPath, List<String> invalidatedFiles,
+      {String outputPath}) async {
     stdoutHandler.reset();
 
     // First time recompile is called we actually have to compile the app from
     // scratch ignoring list of invalidated files.
     if (_server == null)
-      return _compile(mainPath);
+      return _compile(mainPath, outputPath);
 
     final String inputKey = new Uuid().generateV4();
     _server.stdin.writeln('recompile $inputKey');
@@ -156,7 +161,7 @@ class ResidentCompiler {
     return stdoutHandler.outputFilename.future;
   }
 
-  Future<String> _compile(String scriptFilename) async {
+  Future<String> _compile(String scriptFilename, String outputPath) async {
     final String frontendServer = artifacts.getArtifactPath(
       Artifact.frontendServerSnapshotForEngineDartSdk
     );
@@ -168,6 +173,9 @@ class ResidentCompiler {
       '--incremental',
       '--strong'
     ];
+    if (outputPath != null) {
+      args.addAll(<String>['--output-dill', outputPath]);
+    }
     if (_trackWidgetCreation) {
       args.add('--track-widget-creation');
     }

packages/flutter_tools/lib/src/devfs.dart

@@ -499,7 +499,8 @@ class DevFS {
         generator.reset();
       }
       final String compiledBinary =
-          await generator.recompile(mainPath, invalidatedFiles);
+          await generator.recompile(mainPath, invalidatedFiles,
+              outputPath: fs.path.join(getBuildDirectory(), 'app.dill'));
       if (compiledBinary != null && compiledBinary.isNotEmpty)
         dirtyEntries.putIfAbsent(
           Uri.parse(target + '.dill'),

packages/flutter_tools/lib/src/flx.dart

@@ -22,6 +22,7 @@ const String defaultManifestPath = 'pubspec.yaml';
 String get defaultFlxOutputPath => fs.path.join(getBuildDirectory(), 'app.flx');
 String get defaultSnapshotPath => fs.path.join(getBuildDirectory(), 'snapshot_blob.bin');
 String get defaultDepfilePath => fs.path.join(getBuildDirectory(), 'snapshot_blob.bin.d');
+String get defaultApplicationKernelPath => fs.path.join(getBuildDirectory(), 'app.dill');
 const String defaultPrivateKeyPath = 'privatekey.der';
 
 const String _kKernelKey = 'kernel_blob.bin';
@@ -34,6 +35,7 @@ Future<Null> build({
   String manifestPath: defaultManifestPath,
   String outputPath,
   String snapshotPath,
+  String applicationKernelFilePath,
   String depfilePath,
   String privateKeyPath: defaultPrivateKeyPath,
   String workingDirPath,
@@ -48,6 +50,7 @@ Future<Null> build({
   depfilePath ??= defaultDepfilePath;
   workingDirPath ??= getAssetBuildDirectory();
   packagesPath ??= fs.path.absolute(PackageMap.globalPackagesPath);
+  applicationKernelFilePath ??= defaultApplicationKernelPath;
   File snapshotFile;
 
   if (!precompiledSnapshot && !previewDart2) {
@@ -70,10 +73,13 @@ Future<Null> build({
 
   DevFSContent kernelContent;
   if (!precompiledSnapshot && previewDart2) {
+    ensureDirectoryExists(applicationKernelFilePath);
+
     final String kernelBinaryFilename = await compile(
       sdkRoot: artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath),
       incrementalCompilerByteStorePath: fs.path.absolute(getIncrementalCompilerByteStoreDirectory()),
       mainPath: fs.file(mainPath).absolute.path,
+      outputFilePath: applicationKernelFilePath,
       trackWidgetCreation: trackWidgetCreation,
     );
     if (kernelBinaryFilename == null) {