const finder (flutter/engine#15668)

engine/src/flutter/BUILD.gn

@@ -37,6 +37,7 @@ group("flutter") {
 
   if (current_toolchain == host_toolchain) {
     public_deps += [ "$flutter_root/shell/testing" ]
+    public_deps += [ "//flutter/tools/const_finder" ]
   }
 
   if (is_fuchsia && using_fuchsia_sdk) {

engine/src/flutter/testing/run_tests.py

@@ -307,8 +307,16 @@ def RunDartTests(build_dir, filter, verbose_dart_snapshot):
       RunDartTest(build_dir, dart_test_file, verbose_dart_snapshot, True)
       RunDartTest(build_dir, dart_test_file, verbose_dart_snapshot, False)
 
+def RunConstFinderTests(build_dir):
+  test_dir = os.path.join(buildroot_dir, 'flutter', 'tools', 'const_finder', 'test')
+  opts = [
+    os.path.join(test_dir, 'const_finder_test.dart'),
+    os.path.join(build_dir, 'gen', 'frontend_server.dart.snapshot'),
+    os.path.join(build_dir, 'flutter_patched_sdk')]
+  RunEngineExecutable(build_dir, os.path.join('dart-sdk', 'bin', 'dart'), None, flags=opts, cwd=test_dir)
+
 def main():
-  parser = argparse.ArgumentParser();
+  parser = argparse.ArgumentParser()
 
   parser.add_argument('--variant', dest='variant', action='store',
       default='host_debug_unopt', help='The engine build variant to run the tests for.');
@@ -344,6 +352,7 @@ def main():
     assert not IsWindows(), "Dart tests can't be run on windows. https://github.com/flutter/flutter/issues/36301."
     dart_filter = args.dart_filter.split(',') if args.dart_filter else None
     RunDartTests(build_dir, dart_filter, args.verbose_dart_snapshot)
+    RunConstFinderTests(build_dir)
 
   if 'java' in types:
     assert not IsWindows(), "Android engine files can't be compiled on Windows."

engine/src/flutter/tools/const_finder/.dart_tool/package_config.json

@@ -0,0 +1,38 @@
+{
+  "configVersion": 2,
+  "packages": [
+    {
+      "name": "args",
+      "rootUri": "../../../../third_party/dart/third_party/pkg/args",
+      "packageUri": "lib/",
+      "languageVersion": "2.0"
+    },
+    {
+      "name": "kernel",
+      "rootUri": "../../../../third_party/dart/pkg/kernel",
+      "packageUri": "lib/",
+      "languageVersion": "2.2"
+    },
+    {
+      "name": "meta",
+      "rootUri": "../../../../third_party/dart/pkg/meta",
+      "packageUri": "lib/",
+      "languageVersion": "1.12"
+    },
+    {
+      "name": "path",
+      "rootUri": "../../../../third_party/dart/third_party/pkg/path",
+      "packageUri": "lib/",
+      "languageVersion": "2.0"
+    },
+    {
+      "name": "const_finder",
+      "rootUri": "../",
+      "packageUri": "lib/",
+      "languageVersion": "2.4"
+    }
+  ],
+  "generated": "2020-01-16T19:11:54.963296Z",
+  "generator": "pub",
+  "generatorVersion": "2.7.0"
+}

engine/src/flutter/tools/const_finder/.gitignore

@@ -0,0 +1,6 @@
+*.dill
+
+!.dart_tool
+!.dart_tool/package_config.json
+!.packages
+!test/fixtures/.packages

engine/src/flutter/tools/const_finder/.packages

@@ -0,0 +1,6 @@
+# Generated by pub on 2020-01-16 11:11:54.947929.
+args:../../../third_party/dart/third_party/pkg/args/lib/
+kernel:../../../third_party/dart/pkg/kernel/lib/
+meta:../../../third_party/dart/pkg/meta/lib/
+path:../../../third_party/dart/third_party/pkg/path/lib/
+const_finder:lib/

engine/src/flutter/tools/const_finder/BUILD.gn

@@ -0,0 +1,23 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+import("//third_party/dart/utils/application_snapshot.gni")
+
+application_snapshot("const_finder") {
+  main_dart = "bin/main.dart"
+  dot_packages = ".packages"
+
+  training_args = [ "--help" ]
+
+  inputs = [
+    "bin/main.dart",
+    "lib/const_finder.dart",
+    ".packages",
+    ".dart_tool/package_config.json",
+  ]
+
+  deps = [
+    "//flutter/flutter_frontend_server:frontend_server",
+  ]
+}

engine/src/flutter/tools/const_finder/README.md

@@ -0,0 +1,11 @@
+# Const Finder
+
+This program uses package:kernel from the Dart SDK in //third_party.
+
+A snapshot is created via the build rules in BUILD.gn. This is then vended
+to the Flutter tool, which uses it to find `const` creations of `IconData`
+classes. The information from this can then be passed to the `font-subset` tool
+to create a smaller icon font file specific to the application.
+
+Once [flutter/flutter#47162](https://github.com/flutter/flutter/issues/47162) is
+resolved, this package should be moved to the flutter tool.

engine/src/flutter/tools/const_finder/bin/main.dart

@@ -0,0 +1,86 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:convert';
+import 'dart:io';
+
+import 'package:args/args.dart';
+import 'package:const_finder/const_finder.dart';
+
+void main(List<String> args) {
+  final ArgParser parser = ArgParser();
+  parser
+    ..addSeparator('Finds constant instances of a specified class from the\n'
+        'specified package, and outputs JSON like the following:')
+    ..addSeparator('''
+  {
+    "constantInstances": [
+      {
+        "codePoint": 59470,
+        "fontFamily": "MaterialIcons",
+        "fontPackage": null,
+        "matchTextDirection": false
+      }
+    ],
+    "nonConstantInstances": [
+      {
+        "file": "file:///Path/to/hello_world/lib/file.dart",
+        "line": 19,
+        "column": 11
+      }
+    ]
+  }''')
+    ..addSeparator('Where the "constantInstances" is a list of objects containing\n'
+        'the properties passed to the const constructor of the class, and\n'
+        '"nonConstantInstances" is a list of source locations of non-constant\n'
+        'creation of the specified class. Non-constant creation cannot be\n'
+        'statically evaluated by this tool, and callers may wish to treat them\n'
+        'as errors. The non-constant creation may include entries that are not\n'
+        'reachable at runtime.')
+    ..addSeparator('Required arguments:')
+    ..addOption('kernel-file',
+        valueHelp: 'path/to/main.dill',
+        help: 'The path to a kernel file to parse, which was created from the '
+            'main-package-uri library.')
+    ..addOption('main-library-uri',
+        help: 'The package: URI to treat as the main entrypoint library '
+            '(the same package used to create the kernel-file).',
+        valueHelp: 'package:hello_world/main.dart')
+    ..addOption('class-library-uri',
+        help: 'The package: URI of the class to find.',
+        valueHelp: 'package:flutter/src/widgets/icon_data.dart')
+    ..addOption('class-name',
+        help: 'The class name for the class to find.', valueHelp: 'IconData')
+    ..addSeparator('Optional arguments:')
+    ..addFlag('pretty',
+        defaultsTo: false,
+        negatable: false,
+        help: 'Pretty print JSON output (defaults to false).')
+    ..addFlag('help',
+        abbr: 'h',
+        defaultsTo: false,
+        negatable: false,
+        help: 'Print usage and exit');
+
+  final ArgResults argResults = parser.parse(args);
+  T getArg<T>(String name) => argResults[name] as T;
+
+  if (getArg<bool>('help')) {
+    stdout.writeln(parser.usage);
+    exit(0);
+  }
+
+  final ConstFinder finder = ConstFinder(
+    kernelFilePath: getArg<String>('kernel-file'),
+    targetLibraryUri: getArg<String>('main-library-uri'),
+    classLibraryUri: getArg<String>('class-library-uri'),
+    className: getArg<String>('class-name'),
+  );
+
+  final JsonEncoder encoder = getArg<bool>('pretty')
+      ? const JsonEncoder.withIndent('  ')
+      : const JsonEncoder();
+
+  stdout.writeln(encoder.convert(finder.findInstances()));
+}

engine/src/flutter/tools/const_finder/lib/const_finder.dart

@@ -0,0 +1,123 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'package:kernel/kernel.dart' hide MapEntry;
+import 'package:meta/meta.dart';
+
+class _ConstVisitor extends RecursiveVisitor<void> {
+  _ConstVisitor(
+    this.kernelFilePath,
+    this.targetLibraryUri,
+    this.classLibraryUri,
+    this.className,
+  )  : assert(kernelFilePath != null),
+        assert(targetLibraryUri != null),
+        assert(classLibraryUri != null),
+        assert(className != null),
+        constantInstances = <Map<String, dynamic>>[],
+        nonConstantLocations = <Map<String, dynamic>>[];
+
+  /// The path to the file to open.
+  final String kernelFilePath;
+
+  /// The library URI for the main entrypoint of the target library.
+  final String targetLibraryUri;
+
+  /// The library URI for the class to find.
+  final String classLibraryUri;
+
+  /// The name of the class to find.
+  final String className;
+
+  final List<Map<String, dynamic>> constantInstances;
+  final List<Map<String, dynamic>> nonConstantLocations;
+
+  bool _matches(Class node) {
+    return node.enclosingLibrary.canonicalName.name == classLibraryUri &&
+      node.name == className;
+  }
+
+  @override
+  void visitConstructorInvocation(ConstructorInvocation node) {
+    final Class parentClass = node.target.parent as Class;
+    if (!_matches(parentClass)) {
+      super.visitConstructorInvocation(node);
+    }
+    nonConstantLocations.add(<String, dynamic>{
+      'file': node.location.file.toString(),
+      'line': node.location.line,
+      'column': node.location.column,
+    });
+  }
+
+  @override
+  void visitInstanceConstantReference(InstanceConstant node) {
+    if (!_matches(node.classNode)) {
+      return;
+    }
+    final Map<String, dynamic> instance = <String, dynamic>{};
+    for (MapEntry<Reference, Constant> kvp in node.fieldValues.entries) {
+      final PrimitiveConstant<dynamic> value = kvp.value as PrimitiveConstant<dynamic>;
+      instance[kvp.key.canonicalName.name] = value.value;
+    }
+    constantInstances.add(instance);
+  }
+}
+
+/// A kernel AST visitor that finds const references.
+class ConstFinder {
+  /// Creates a new ConstFinder class.  All arguments are required and must not
+  /// be null.
+  ///
+  /// The `kernelFilePath` is the path to a dill (kernel) file to process.
+  ///
+  /// The `targetLibraryUri` is the `package:` URI of the main entrypoint to
+  /// search from.
+  ///
+  ///
+  ///
+  ConstFinder({
+    @required String kernelFilePath,
+    @required String targetLibraryUri,
+    @required String classLibraryUri,
+    @required String className,
+  })  : _visitor = _ConstVisitor(
+                    kernelFilePath,
+                    targetLibraryUri,
+                    classLibraryUri,
+                    className,
+                  );
+
+  final _ConstVisitor _visitor;
+
+  Library _getRoot() {
+    final Component binary = loadComponentFromBinary(_visitor.kernelFilePath);
+    return binary.libraries.firstWhere(
+      (Library library) => library.canonicalName.name == _visitor.targetLibraryUri,
+      orElse: () => throw LibraryNotFoundException._(_visitor.targetLibraryUri),
+    );
+  }
+
+  /// Finds all instances
+  Map<String, dynamic> findInstances() {
+    final Library root = _getRoot();
+    root.visitChildren(_visitor);
+    return <String, dynamic>{
+      'constantInstances': _visitor.constantInstances,
+      'nonConstantLocations': _visitor.nonConstantLocations,
+    };
+  }
+}
+
+/// Exception thrown by [ConstFinder.findInstances] when the target library
+/// is not found.
+class LibraryNotFoundException implements Exception {
+  const LibraryNotFoundException._(this.targetLibraryUri);
+
+  /// The library target URI that could not be found.
+  final String targetLibraryUri;
+
+  @override
+  String toString() => 'Could not find target library for "$targetLibraryUri".';
+}

engine/src/flutter/tools/const_finder/pubspec.yaml

@@ -0,0 +1,35 @@
+# Copyright 2013 The Flutter Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+name: const_finder
+publish_to: none
+
+environment:
+  sdk: ">=2.4.0 <3.0.0"
+
+# Do not add any dependencies that require more than what is provided in
+# //third_party/dart/pkg or //third_party/dart/third_party/pkg.
+# In particular, package:test is not usable here.
+
+# If you do add packages here, make sure you can run `pub get --offline`, and
+# check the .packages and .package_config to make sure all the paths are
+# relative to this directory into //third_party/dart
+
+dependencies:
+  args: any
+  meta: any
+  kernel: any
+
+dev_dependencies:
+  path: any
+
+dependency_overrides:
+  args:
+    path: ../../../third_party/dart/third_party/pkg/args
+  kernel:
+    path: ../../../third_party/dart/pkg/kernel
+  meta:
+    path: ../../../third_party/dart/pkg/meta
+  path:
+    path: ../../../third_party/dart/third_party/pkg/path

engine/src/flutter/tools/const_finder/test/const_finder_test.dart

@@ -0,0 +1,136 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:convert' show jsonEncode;
+import 'dart:io';
+
+import 'package:const_finder/const_finder.dart';
+import 'package:path/path.dart' as path;
+
+void expect<T>(T value, T expected) {
+  if (value != expected) {
+    stderr.writeln('Expected: $expected');
+    stderr.writeln('Actual:   $value');
+    exitCode = -1;
+  }
+}
+
+final String basePath =
+    path.canonicalize(path.join(path.dirname(Platform.script.path), '..'));
+final String fixtures = path.join(basePath, 'test', 'fixtures');
+final String consts = path.join(fixtures, 'lib', 'consts.dart');
+final String dotPackages = path.join(fixtures, '.packages');
+final String constsAndNon = path.join(fixtures, 'lib', 'consts_and_non.dart');
+final String constsDill = path.join(fixtures, 'consts.dill');
+final String constsAndNonDill = path.join(fixtures, 'consts_and_non.dill');
+
+// This test is assuming the `dart` used to invoke the tests is compatible
+// with the version of package:kernel in //third-party/dart/pkg/kernel
+final String dart = Platform.resolvedExecutable;
+final String bat = Platform.isWindows ? '.bat' : '';
+
+void _checkConsts() {
+  print('Checking for expected constants.');
+  final ConstFinder finder = ConstFinder(
+    kernelFilePath: constsDill,
+    targetLibraryUri: 'package:const_finder_fixtures/consts.dart',
+    classLibraryUri: 'package:const_finder_fixtures/target.dart',
+    className: 'Target',
+  );
+
+  expect<String>(
+    jsonEncode(finder.findInstances()),
+    jsonEncode(<String, dynamic>{
+      'constantInstances': <Map<String, dynamic>>[
+        <String, dynamic>{'stringValue': '1', 'intValue': 1},
+        <String, dynamic>{'stringValue': '2', 'intValue': 2}
+      ],
+      'nonConstantLocations': <dynamic>[],
+    }),
+  );
+}
+
+void _checkNonConsts() {
+  print('Checking for non-constant instances.');
+  final ConstFinder finder = ConstFinder(
+    kernelFilePath: constsAndNonDill,
+    targetLibraryUri: 'package:const_finder_fixtures/consts_and_non.dart',
+    classLibraryUri: 'package:const_finder_fixtures/target.dart',
+    className: 'Target',
+  );
+
+  expect<String>(
+    jsonEncode(finder.findInstances()),
+    jsonEncode(<String, dynamic>{
+      'constantInstances': <dynamic>[
+        <String, dynamic>{'stringValue': '1', 'intValue': 1}
+      ],
+      'nonConstantLocations': <dynamic>[
+        <String, dynamic>{
+          'file': 'file://$fixtures/lib/consts_and_non.dart',
+          'line': 12,
+          'column': 26
+        },
+        <String, dynamic>{
+          'file': 'file://$fixtures/lib/consts_and_non.dart',
+          'line': 14,
+          'column': 26
+        },
+      ]
+    }),
+  );
+}
+
+Future<void> main(List<String> args) async {
+  if (args.length != 2) {
+    stderr.writeln('The first argument must be the path to the forntend server dill.');
+    stderr.writeln('The second argument must be the path to the flutter_patched_sdk');
+    exit(-1);
+  }
+  final String frontendServer = args[0];
+  final String sdkRoot = args[1];
+  try {
+    void _checkProcessResult(ProcessResult result) {
+      if (result.exitCode != 0) {
+        stdout.writeln(result.stdout);
+        stderr.writeln(result.stderr);
+      }
+      expect(result.exitCode, 0);
+    }
+
+    stdout.writeln('Generating kernel fixtures...');
+    stdout.writeln(consts);
+    _checkProcessResult(Process.runSync(dart, <String>[
+      frontendServer,
+      '--sdk-root=$sdkRoot',
+      '--target=flutter',
+      '--aot',
+      '--tfa',
+      '--packages=$dotPackages',
+      '--output-dill=$constsDill',
+      consts,
+    ]));
+
+    _checkProcessResult(Process.runSync(dart, <String>[
+      frontendServer,
+      '--sdk-root=$sdkRoot',
+      '--target=flutter',
+      '--aot',
+      '--tfa',
+      '--packages=$dotPackages',
+      '--output-dill=$constsAndNonDill',
+      constsAndNon,
+    ]));
+
+    _checkConsts();
+    _checkNonConsts();
+  } finally {
+    try {
+      File(constsDill).deleteSync();
+      File(constsAndNonDill).deleteSync();
+    } finally {
+      stdout.writeln('Tests ${exitCode == 0 ? 'succeeded' : 'failed'} - exit code: $exitCode');
+    }
+  }
+}

engine/src/flutter/tools/const_finder/test/fixtures/.packages

@@ -0,0 +1,2 @@
+# Generated by pub on 2020-01-15 10:08:29.776333.
+const_finder_fixtures:lib/

engine/src/flutter/tools/const_finder/test/fixtures/lib/consts.dart

@@ -0,0 +1,17 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+import 'dart:core';
+
+import 'target.dart';
+
+void main() {
+  const Target target1 = Target('1', 1);
+  const Target target2 = Target('2', 2);
+  // ignore: unused_local_variable
+  const Target target3 = Target('3', 3); // should be tree shaken out.
+  target1.hit();
+  target2.hit();
+}
+

engine/src/flutter/tools/const_finder/test/fixtures/lib/consts_and_non.dart

@@ -0,0 +1,17 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// ignore_for_file: prefer_const_constructors
+import 'dart:core';
+
+import 'target.dart';
+
+void main() {
+  const Target target1 = Target('1', 1);
+  final Target target2 = Target('2', 2);
+  // ignore: unused_local_variable
+  final Target target3 = Target('3', 3); // should be tree shaken out.
+  target1.hit();
+  target2.hit();
+}

engine/src/flutter/tools/const_finder/test/fixtures/lib/target.dart

@@ -0,0 +1,14 @@
+// Copyright 2013 The Flutter Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+class Target {
+  const Target(this.stringValue, this.intValue);
+
+  final String stringValue;
+  final int intValue;
+
+  void hit() {
+    print('$stringValue $intValue');
+  }
+}