Extract kernel compile from buildAotSnapshot (#17062)

Moves the kernel compile step to the beginning of the AOT build in a
separate method. This is pre-factoring for iOS universal builds where
the kernel build happens once, but we then snapshot twice: once for
armv7 and once for arm64.

This also writes dependencies to build/kernel_compile.d rather than
build/aot/snapshot.d, since that is immediately overwritten by
gen_snapshot.

packages/flutter_tools/lib/src/base/build.dart

@@ -207,6 +207,52 @@ class Snapshotter {
     return exitCode;
   }
 
+  /// Compiles a Dart file to kernel.
+  ///
+  /// Returns the output kernel file path, or null on failure.
+  Future<String> compileKernel({
+    @required TargetPlatform platform,
+    @required BuildMode buildMode,
+    @required String mainPath,
+    @required String outputPath,
+    List<String> extraFrontEndOptions: const <String>[],
+  }) async {
+    final Directory outputDir = fs.directory(outputPath);
+    outputDir.createSync(recursive: true);
+
+    printTrace('Compiling Dart to kernel: $mainPath');
+    final bool aot = !_isInterpreted(platform, buildMode);
+    final List<String> entryPointsJsonFiles = <String>[];
+    if (aot) {
+      entryPointsJsonFiles.addAll(<String>[
+        artifacts.getArtifactPath(Artifact.entryPointsJson, platform, buildMode),
+        artifacts.getArtifactPath(Artifact.entryPointsExtraJson, platform, buildMode),
+      ]);
+    }
+
+    if ((extraFrontEndOptions != null) && extraFrontEndOptions.isNotEmpty)
+      printTrace('Extra front-end options: $extraFrontEndOptions');
+
+    final String depfilePath = fs.path.join(outputPath, 'kernel_compile.d');
+    final CompilerOutput compilerOutput = await kernelCompiler.compile(
+      sdkRoot: artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath),
+      mainPath: mainPath,
+      outputFilePath: fs.path.join(outputPath, 'app.dill'),
+      depFilePath: depfilePath,
+      extraFrontEndOptions: extraFrontEndOptions,
+      linkPlatformKernelIn: true,
+      aot: aot,
+      entryPointsJsonFiles: entryPointsJsonFiles,
+      trackWidgetCreation: false,
+    );
+
+    // Write path to frontend_server, since things need to be re-generated when that changes.
+    final String frontendPath = artifacts.getArtifactPath(Artifact.frontendServerSnapshotForEngineDartSdk);
+    await fs.directory(outputPath).childFile('frontend_server.d').writeAsString('frontend_server.d: $frontendPath\n');
+
+    return compilerOutput?.outputFilename;
+  }
+
   /// Builds an architecture-specific ahead-of-time compiled snapshot of the specified script.
   Future<int> buildAotSnapshot({
     @required TargetPlatform platform,
@@ -216,7 +262,6 @@ class Snapshotter {
     @required String outputPath,
     @required bool previewDart2,
     @required bool preferSharedLibrary,
-    List<String> extraFrontEndOptions: const <String>[],
     List<String> extraGenSnapshotOptions: const <String>[],
   }) async {
     if (!(platform == TargetPlatform.android_arm ||
@@ -228,6 +273,7 @@ class Snapshotter {
 
     final Directory outputDir = fs.directory(outputPath);
     outputDir.createSync(recursive: true);
+
     final String vmSnapshotData = fs.path.join(outputDir.path, 'vm_snapshot_data');
     final String vmSnapshotInstructions = fs.path.join(outputDir.path, 'vm_snapshot_instr');
     final String isolateSnapshotData = fs.path.join(outputDir.path, 'isolate_snapshot_data');
@@ -250,15 +296,6 @@ class Snapshotter {
     final String ioEntryPoints = artifacts.getArtifactPath(Artifact.dartIoEntriesTxt, platform, buildMode);
     assert(ioEntryPoints != null);
 
-    final bool interpreter = platform == TargetPlatform.ios && buildMode == BuildMode.debug;
-    final List<String> entryPointsJsonFiles = <String>[];
-    if (previewDart2 && !interpreter) {
-      entryPointsJsonFiles.addAll(<String>[
-        artifacts.getArtifactPath(Artifact.entryPointsJson, platform, buildMode),
-        artifacts.getArtifactPath(Artifact.entryPointsExtraJson, platform, buildMode),
-      ]);
-    }
-
     final PackageMap packageMap = new PackageMap(packagesPath);
     final String packageMapError = packageMap.checkValid();
     if (packageMapError != null) {
@@ -278,8 +315,6 @@ class Snapshotter {
       mainPath,
     ];
 
-    inputPaths.addAll(entryPointsJsonFiles);
-
     final Set<String> outputPaths = new Set<String>();
 
     // These paths are used only on iOS.
@@ -325,14 +360,12 @@ class Snapshotter {
       '--dependencies=$depfilePath',
     ];
 
-    if ((extraFrontEndOptions != null) && extraFrontEndOptions.isNotEmpty)
-      printTrace('Extra front-end options: $extraFrontEndOptions');
-
     if ((extraGenSnapshotOptions != null) && extraGenSnapshotOptions.isNotEmpty) {
       printTrace('Extra gen-snapshot options: $extraGenSnapshotOptions');
       genSnapshotArgs.addAll(extraGenSnapshotOptions);
     }
 
+    final bool interpreter = _isInterpreted(platform, buildMode);
     if (!interpreter) {
       genSnapshotArgs.add('--embedder_entry_points_manifest=$vmEntryPoints');
       genSnapshotArgs.add('--embedder_entry_points_manifest=$ioEntryPoints');
@@ -347,7 +380,6 @@ class Snapshotter {
     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:
@@ -408,36 +440,13 @@ class Snapshotter {
       return 0;
     }
 
-    String entrypointPath = mainPath;
     if (previewDart2) {
-      final CompilerOutput compilerOutput = await kernelCompiler.compile(
-        sdkRoot: artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath),
-        mainPath: mainPath,
-        outputFilePath: kApplicationKernelPath,
-        depFilePath: depfilePath,
-        extraFrontEndOptions: extraFrontEndOptions,
-        linkPlatformKernelIn: true,
-        aot: !interpreter,
-        entryPointsJsonFiles: entryPointsJsonFiles,
-        trackWidgetCreation: false,
-      );
-      entrypointPath = compilerOutput?.outputFilename;
-      if (entrypointPath == null) {
-        printError('Compiler terminated unexpectedly.');
-        return -5;
-      }
-      // Write path to frontend_server, since things need to be re-generated when
-      // that changes.
-      await outputDir.childFile('frontend_server.d')
-          .writeAsString('frontend_server.d: ${artifacts.getArtifactPath(Artifact.frontendServerSnapshotForEngineDartSdk)}\n');
-
       genSnapshotArgs.addAll(<String>[
         '--reify-generic-functions',
         '--strong',
       ]);
     }
-
-    genSnapshotArgs.add(entrypointPath);
+    genSnapshotArgs.add(mainPath);
 
     final int genSnapshotExitCode = await genSnapshot.run(
       snapshotType: new SnapshotType(platform, buildMode),
@@ -517,6 +526,11 @@ class Snapshotter {
     return 0;
   }
 
+  /// Returns true if the specified platform and build mode require running in interpreted mode.
+  bool _isInterpreted(TargetPlatform platform, BuildMode buildMode) {
+    return platform == TargetPlatform.ios && buildMode == BuildMode.debug;
+  }
+
   String _getPackagePath(PackageMap packageMap, String package) {
     return fs.path.dirname(fs.path.fromUri(packageMap.map[package]));
   }

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

@@ -54,29 +54,50 @@ class BuildAotCommand extends BuildSubCommand {
   @override
   Future<Null> runCommand() async {
     await super.runCommand();
+
     final String targetPlatform = argResults['target-platform'];
     final TargetPlatform platform = getTargetPlatformForName(targetPlatform);
     if (platform == null)
       throwToolExit('Unknown platform: $targetPlatform');
 
-    final String typeName = artifacts.getEngineType(platform, getBuildMode());
+    final BuildMode buildMode = getBuildMode();
+
     Status status;
     if (!argResults['quiet']) {
+      final String typeName = artifacts.getEngineType(platform, buildMode);
       status = logger.startProgress('Building AOT snapshot in ${getModeName(getBuildMode())} mode ($typeName)...',
           expectSlowOperation: true);
     }
     final String outputPath = argResults['output-dir'] ?? getAotBuildDirectory();
     try {
+      final bool previewDart2 = argResults['preview-dart-2'];
+      String mainPath = findMainDartFile(targetFile);
       final Snapshotter snapshotter = new Snapshotter();
+
+      // Compile to kernel, if Dart 2.
+      if (previewDart2) {
+        mainPath = await snapshotter.compileKernel(
+          platform: platform,
+          buildMode: buildMode,
+          mainPath: mainPath,
+          outputPath: outputPath,
+          extraFrontEndOptions: argResults[FlutterOptions.kExtraFrontEndOptions],
+        );
+        if (mainPath == null) {
+          printError('Compiler terminated unexpectedly.');
+          return;
+        }
+      }
+
+      // Build AOT snapshot.
       final int snapshotExitCode = await snapshotter.buildAotSnapshot(
         platform: platform,
-        buildMode: getBuildMode(),
-        mainPath: findMainDartFile(targetFile),
+        buildMode: buildMode,
+        mainPath: mainPath,
         packagesPath: PackageMap.globalPackagesPath,
         outputPath: outputPath,
-        previewDart2: argResults['preview-dart-2'],
+        previewDart2: previewDart2,
         preferSharedLibrary: argResults['prefer-shared-library'],
-        extraFrontEndOptions: argResults[FlutterOptions.kExtraFrontEndOptions],
         extraGenSnapshotOptions: argResults[FlutterOptions.kExtraGenSnapshotOptions],
       );
       if (snapshotExitCode != 0) {

packages/flutter_tools/test/base/build_test.dart

@@ -9,7 +9,6 @@ import 'dart:convert' show json;
 import 'package:file/memory.dart';
 import 'package:flutter_tools/src/artifacts.dart';
 import 'package:flutter_tools/src/build_info.dart';
-import 'package:flutter_tools/src/compile.dart';
 import 'package:flutter_tools/src/base/build.dart';
 import 'package:flutter_tools/src/base/context.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
@@ -70,29 +69,6 @@ class _FakeGenSnapshot implements GenSnapshot {
   }
 }
 
-class _FakeKernelCompiler implements KernelCompiler {
-  CompilerOutput output;
-
-  @override
-  Future<CompilerOutput> compile({
-    String sdkRoot,
-    String mainPath,
-    String outputFilePath,
-    String depFilePath,
-    bool linkPlatformKernelIn: false,
-    bool aot: false,
-    List<String> entryPointsJsonFiles,
-    bool trackWidgetCreation: false,
-    List<String> extraFrontEndOptions,
-    String incrementalCompilerByteStorePath,
-    String packagesPath,
-    List<String> fileSystemRoots,
-    String fileSystemScheme,
-  }) async {
-    return output;
-  }
-}
-
 void main() {
   group('SnapshotType', () {
     test('throws, if build mode is null', () {
@@ -606,7 +582,6 @@ void main() {
     String skyEnginePath;
 
     _FakeGenSnapshot genSnapshot;
-    _FakeKernelCompiler kernelCompiler;
     MemoryFileSystem fs;
     Snapshotter snapshotter;
     MockArtifacts mockArtifacts;
@@ -630,7 +605,6 @@ void main() {
       fs.file(fs.path.join(skyEnginePath, 'sdk_ext', 'vmservice_io.dart')).createSync();
 
       genSnapshot = new _FakeGenSnapshot();
-      kernelCompiler = new _FakeKernelCompiler();
       snapshotter = new Snapshotter();
       mockArtifacts = new MockArtifacts();
       mockXcode = new MockXcode();
@@ -648,18 +622,16 @@ void main() {
       Artifacts: () => mockArtifacts,
       FileSystem: () => fs,
       GenSnapshot: () => genSnapshot,
-      KernelCompiler: () => kernelCompiler,
       Xcode: () => mockXcode,
       Xxd: () => mockXxd,
     };
 
     testUsingContext('builds iOS debug AOT snapshot', () async {
-      fs.file('main.dart').writeAsStringSync('void main() {}');
+      fs.file('main.dill').writeAsStringSync('binary magic');
 
       final String outputPath = fs.path.join('build', 'foo');
       fs.directory(outputPath).createSync(recursive: true);
 
-      kernelCompiler.output = const CompilerOutput('main.dill', 0);
       genSnapshot.outputs = <String, String>{
         fs.path.join(outputPath, 'vm_snapshot_data'): '',
         fs.path.join(outputPath, 'vm_snapshot_instr'): '',
@@ -672,7 +644,7 @@ void main() {
       final int genSnapshotExitCode = await snapshotter.buildAotSnapshot(
         platform: TargetPlatform.ios,
         buildMode: BuildMode.debug,
-        mainPath: 'main.dart',
+        mainPath: 'main.dill',
         packagesPath: '.packages',
         outputPath: outputPath,
         preferSharedLibrary: false,
@@ -701,12 +673,11 @@ void main() {
     }, overrides: contextOverrides);
 
     testUsingContext('builds iOS profile AOT snapshot', () async {
-      fs.file('main.dart').writeAsStringSync('void main() {}');
+      fs.file('main.dill').writeAsStringSync('binary magic');
 
       final String outputPath = fs.path.join('build', 'foo');
       fs.directory(outputPath).createSync(recursive: true);
 
-      kernelCompiler.output = const CompilerOutput('main.dill', 0);
       genSnapshot.outputs = <String, String>{
         fs.path.join(outputPath, 'snapshot_assembly.S'): '',
         fs.path.join(outputPath, 'snapshot.d'): '',
@@ -715,7 +686,7 @@ void main() {
       final int genSnapshotExitCode = await snapshotter.buildAotSnapshot(
         platform: TargetPlatform.ios,
         buildMode: BuildMode.profile,
-        mainPath: 'main.dart',
+        mainPath: 'main.dill',
         packagesPath: '.packages',
         outputPath: outputPath,
         preferSharedLibrary: false,
@@ -746,12 +717,11 @@ void main() {
     }, overrides: contextOverrides);
 
     testUsingContext('builds iOS release AOT snapshot', () async {
-      fs.file('main.dart').writeAsStringSync('void main() {}');
+      fs.file('main.dill').writeAsStringSync('binary magic');
 
       final String outputPath = fs.path.join('build', 'foo');
       fs.directory(outputPath).createSync(recursive: true);
 
-      kernelCompiler.output = const CompilerOutput('main.dill', 0);
       genSnapshot.outputs = <String, String>{
         fs.path.join(outputPath, 'snapshot_assembly.S'): '',
         fs.path.join(outputPath, 'snapshot.d'): '',
@@ -760,7 +730,7 @@ void main() {
       final int genSnapshotExitCode = await snapshotter.buildAotSnapshot(
         platform: TargetPlatform.ios,
         buildMode: BuildMode.release,
-        mainPath: 'main.dart',
+        mainPath: 'main.dill',
         packagesPath: '.packages',
         outputPath: outputPath,
         preferSharedLibrary: false,