Faster hot reload (#8600)

This implements the `DartDependencySetBuilder` completely in Dart instead of calling out to `sky_snapshot` (Linux/Mac) or `gen_snapshot` (Windows) and allows us to use the same code path on all supported host platforms.

It also slightly reduces hot reload times on Linux from ~750ms to ~690ms for the unchanged flutter_gallery app and significantly reduces hot reload times on Windows from almost 1.5s to just slightly slower than on Linux.

This change will also allow us to retire `sky_snapshot` completely in the future.

packages/flutter_tools/lib/src/dart/dependencies.dart

@@ -2,89 +2,49 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-import 'dart:convert';
+import 'package:analyzer/analyzer.dart';
 
-import '../artifacts.dart';
 import '../base/file_system.dart';
-import '../base/platform.dart';
-import '../base/process.dart';
+import '../dart/package_map.dart';
 
 class DartDependencySetBuilder {
+  DartDependencySetBuilder(String mainScriptPath, String packagesFilePath) :
+        this._mainScriptPath = fs.path.canonicalize(mainScriptPath),
+        this._mainScriptUri = fs.path.toUri(mainScriptPath),
+        this._packagesFilePath = fs.path.canonicalize(packagesFilePath);
 
-  factory DartDependencySetBuilder(
-      String mainScriptPath, String projectRootPath, String packagesFilePath) {
-    if (platform.isWindows)
-      return new _GenSnapshotDartDependencySetBuilder(mainScriptPath, projectRootPath, packagesFilePath);
-    return new DartDependencySetBuilder._(mainScriptPath, projectRootPath, packagesFilePath);
-  }
-
-  DartDependencySetBuilder._(this.mainScriptPath, this.projectRootPath, this.packagesFilePath);
+  final String _mainScriptPath;
+  final String _packagesFilePath;
 
-  final String mainScriptPath;
-  final String projectRootPath;
-  final String packagesFilePath;
+  final Uri _mainScriptUri;
 
-  /// Returns a set of canonicalize paths.
-  ///
-  /// The paths have been canonicalize with `fs.path.canonicalize`.
   Set<String> build() {
-    final String skySnapshotPath =
-        Artifacts.instance.getArtifactPath(Artifact.skySnapshot);
-
-    final List<String> args = <String>[
-      skySnapshotPath,
-      '--packages=$packagesFilePath',
-      '--print-deps',
-      mainScriptPath
-    ];
-
-    final String output = runSyncAndThrowStdErrOnError(args);
-
-    return new Set<String>.from(LineSplitter.split(output).map(
-        (String path) => fs.path.canonicalize(path))
-    );
+    final List<String> dependencies = <String>[_mainScriptPath, _packagesFilePath];
+    final List<Uri> toProcess = <Uri>[_mainScriptUri];
+    final PackageMap packageMap = new PackageMap(_packagesFilePath);
+
+    while (toProcess.isNotEmpty) {
+      final Uri currentUri = toProcess.removeLast();
+      final CompilationUnit unit = _parse(currentUri.toFilePath());
+      for (Directive directive in unit.directives) {
+        if (!(directive is UriBasedDirective))
+          continue;
+        final UriBasedDirective uriBasedDirective = directive;
+        final String uriAsString = uriBasedDirective.uri.stringValue;
+        Uri resolvedUri = resolveRelativeUri(currentUri, Uri.parse(uriAsString));
+        if (resolvedUri.scheme.startsWith('dart'))
+          continue;
+        if (resolvedUri.scheme == 'package')
+          resolvedUri = packageMap.uriForPackage(resolvedUri);
+        final String path = fs.path.canonicalize(resolvedUri.toFilePath());
+        if (!dependencies.contains(path)) {
+          dependencies.add(path);
+          toProcess.add(resolvedUri);
+        }
       }
-}
-
-/// A [DartDependencySetBuilder] that is backed by gen_snapshot.
-class _GenSnapshotDartDependencySetBuilder implements DartDependencySetBuilder {
-  _GenSnapshotDartDependencySetBuilder(this.mainScriptPath,
-                                       this.projectRootPath,
-                                       this.packagesFilePath);
-
-  @override
-  final String mainScriptPath;
-  @override
-  final String projectRootPath;
-  @override
-  final String packagesFilePath;
-
-  @override
-  Set<String> build() {
-    final String snapshotterPath =
-        Artifacts.instance.getArtifactPath(Artifact.genSnapshot);
-    final String vmSnapshotData =
-        Artifacts.instance.getArtifactPath(Artifact.vmSnapshotData);
-    final String isolateSnapshotData =
-        Artifacts.instance.getArtifactPath(Artifact.isolateSnapshotData);
-    assert(fs.path.isAbsolute(this.projectRootPath));
-
-    final List<String> args = <String>[
-      snapshotterPath,
-      '--snapshot_kind=script',
-      '--dependencies-only',
-      '--vm_snapshot_data=$vmSnapshotData',
-      '--isolate_snapshot_data=$isolateSnapshotData',
-      '--packages=$packagesFilePath',
-      '--print-dependencies',
-      '--script_snapshot=snapshot_blob.bin',
-      mainScriptPath
-    ];
-
-    final String output = runSyncAndThrowStdErrOnError(args);
-
-    return new Set<String>.from(LineSplitter.split(output).map(
-            (String path) => fs.path.canonicalize(path))
-    );
     }
+    return dependencies.toSet();
+  }
+
+  CompilationUnit _parse(String path) => parseDirectives(fs.file(path).readAsStringSync(), name: path);
 }

packages/flutter_tools/lib/src/dart/package_map.dart

@@ -40,13 +40,16 @@ class PackageMap {
   Map<String, Uri> _map;
 
   /// Returns the path to [packageUri].
-  String pathForPackage(Uri packageUri) {
+  String pathForPackage(Uri packageUri) => uriForPackage(packageUri).path;
+
+  /// Returns the path to [packageUri] as Uri.
+  Uri uriForPackage(Uri packageUri) {
     assert(packageUri.scheme == 'package');
     final List<String> pathSegments = packageUri.pathSegments.toList();
     final String packageName = pathSegments.removeAt(0);
     final Uri packageBase = map[packageName];
     final String packageRelativePath = fs.path.joinAll(pathSegments);
-    return packageBase.resolve(packageRelativePath).path;
+    return packageBase.resolveUri(fs.path.toUri(packageRelativePath));
   }
 
   String checkValid() {

packages/flutter_tools/lib/src/dependency_checker.dart

@@ -17,12 +17,6 @@ class DependencyChecker {
   /// if it cannot be determined.
   bool check(DateTime threshold) {
     _dependencies.clear();
-    try {
-      _dependencies.add(builder.packagesFilePath);
-    } catch (e, st) {
-      printTrace('DependencyChecker: could not parse .packages file:\n$e\n$st');
-      return true;
-    }
     // Build the set of Dart dependencies.
     try {
       _dependencies.addAll(builder.build());

packages/flutter_tools/lib/src/resident_runner.dart

@@ -330,8 +330,7 @@ abstract class ResidentRunner {
 
   bool hasDirtyDependencies() {
     final DartDependencySetBuilder dartDependencySetBuilder =
-        new DartDependencySetBuilder(
-            mainPath, projectRootPath, packagesFilePath);
+        new DartDependencySetBuilder(mainPath, packagesFilePath);
     final DependencyChecker dependencyChecker =
         new DependencyChecker(dartDependencySetBuilder, assetBundle);
     final String path = package.packagePath;

packages/flutter_tools/lib/src/run_hot.dart

@@ -99,8 +99,7 @@ class HotRunner extends ResidentRunner {
       return true;
     }
     final DartDependencySetBuilder dartDependencySetBuilder =
-        new DartDependencySetBuilder(
-              mainPath, projectRootPath, packagesFilePath);
+        new DartDependencySetBuilder(mainPath, packagesFilePath);
     try {
       _dartDependencies = new Set<String>.from(dartDependencySetBuilder.build());
     } catch (error) {

packages/flutter_tools/test/dart_dependencies_test.dart

@@ -2,6 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
+import 'package:analyzer/analyzer.dart';
 import 'package:flutter_tools/src/dart/dependencies.dart';
 import 'package:flutter_tools/src/base/file_system.dart';
 import 'package:flutter_tools/src/base/platform.dart';
@@ -17,7 +18,7 @@ void main()  {
       final String mainPath = fs.path.join(testPath, 'main.dart');
       final String packagesPath = fs.path.join(testPath, '.packages');
       final DartDependencySetBuilder builder =
-          new DartDependencySetBuilder(mainPath, testPath, packagesPath);
+          new DartDependencySetBuilder(mainPath, packagesPath);
       final Set<String> dependencies = builder.build();
       expect(dependencies.contains(fs.path.canonicalize(mainPath)), isTrue);
       expect(dependencies.contains(fs.path.canonicalize(fs.path.join(testPath, 'foo.dart'))), isTrue);
@@ -27,13 +28,12 @@ void main()  {
       final String mainPath = fs.path.join(testPath, 'main.dart');
       final String packagesPath = fs.path.join(testPath, '.packages');
       final DartDependencySetBuilder builder =
-          new DartDependencySetBuilder(mainPath, testPath, packagesPath);
+          new DartDependencySetBuilder(mainPath, packagesPath);
       try {
         builder.build();
         fail('expect an assertion to be thrown.');
-      } catch (e) {
-        expect(e, const isInstanceOf<String>());
-        expect(e.contains('unexpected token \'bad\''), isTrue);
+      } on AnalyzerErrorGroup catch (e) {
+        expect(e.toString(), contains('foo.dart: Expected a string literal'));
       }
     });
   });

packages/flutter_tools/test/data/dart_dependencies_test/syntax_error/foo.dart

@@ -2,4 +2,4 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-bad programmer!
+import bad programmer!

packages/flutter_tools/test/dependency_checker_test.dart

@@ -31,7 +31,7 @@ void main()  {
       final String barPath = fs.path.join(testPath, 'lib', 'bar.dart');
       final String packagesPath = fs.path.join(testPath, '.packages');
       final DartDependencySetBuilder builder =
-          new DartDependencySetBuilder(mainPath, testPath, packagesPath);
+          new DartDependencySetBuilder(mainPath, packagesPath);
       final DependencyChecker dependencyChecker =
           new DependencyChecker(builder, null);
 
@@ -63,7 +63,7 @@ void main()  {
       final String packagesPath = fs.path.join(testPath, '.packages');
 
       final DartDependencySetBuilder builder =
-          new DartDependencySetBuilder(mainPath, testPath, packagesPath);
+          new DartDependencySetBuilder(mainPath, packagesPath);
       final DependencyChecker dependencyChecker =
           new DependencyChecker(builder, null);