First step for modular output in fasta.

pkg/front_end/test/fasta/shaker_test.dart

Index: pkg/front_end/test/fasta/shaker_test.dart
diff --git a/pkg/front_end/test/fasta/shaker_test.dart b/pkg/front_end/test/fasta/shaker_test.dart
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+// Copyright (c) 2017, the Dart project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE.md file.
+
+/// Tests basic functionality of the API tree-shaker.
+///
+/// Each input file is built and tree-shaken, then we check that the set of
+/// libraries, classes, and members that are retained match those declared in an
+/// expectations file.
+///
+/// Input files may contain markers to turn on flags that configure this
+/// runner. Currently only the following marker is recognized:
+///   @@SHOW_CORE_LIBRARIES@@ - whether to check for retained information from
+///      the core libraries. By default this runner only checks for members of
+///      pkg/front_end/testcases/shaker/lib/lib.dart.
+library fasta.test.shaker_test;
+
+import 'dart:async' show Future;
+import 'dart:convert' show JSON;
+import 'dart:io' show File;
+
+export 'package:testing/testing.dart' show Chain, runMe;
+import 'package:front_end/physical_file_system.dart';
+import 'package:front_end/src/fasta/dill/dill_target.dart' show DillTarget;
+import 'package:front_end/src/fasta/errors.dart' show InputError;
+import 'package:front_end/src/fasta/kernel/kernel_target.dart'
+    show KernelTarget;
+import 'package:front_end/src/fasta/kernel/verifier.dart' show verifyProgram;
+import 'package:front_end/src/fasta/testing/kernel_chain.dart' show runDiff;
+import 'package:front_end/src/fasta/testing/patched_sdk_location.dart';
+import 'package:front_end/src/fasta/ticker.dart' show Ticker;
+import 'package:front_end/src/fasta/translate_uri.dart' show TranslateUri;
+import 'package:front_end/src/fasta/util/relativize.dart' show relativizeUri;
+import 'package:kernel/ast.dart' show Program;
+import 'package:kernel/kernel.dart' show loadProgramFromBytes;
+import 'package:testing/testing.dart'
+    show Chain, ChainContext, ExpectationSet, Result, Step, TestDescription;
+import 'testing/suite.dart';
+
+main(List<String> arguments) => runMe(arguments, createContext, "testing.json");
+
+Future<TreeShakerContext> createContext(
+    Chain suite, Map<String, String> environment) {
+  return TreeShakerContext.create(environment);
+}
+
+/// Context used to run the tree-shaking test suite.
+class TreeShakerContext extends ChainContext {
+  final TranslateUri uriTranslator;
+  final Uri outlineUri;
+  final List<Step> steps;
+  final List<int> outlineBytes;
+
+  final ExpectationSet expectationSet =
+      new ExpectationSet.fromJsonList(JSON.decode(EXPECTATIONS));
+
+  TreeShakerContext(this.outlineUri, this.uriTranslator, this.outlineBytes,
+      bool updateExpectations)
+      : steps = <Step>[
+          const BuildProgram(),
+          new CheckShaker(updateExpectations: updateExpectations),
+        ];
+
+  Program loadPlatformOutline() {
+    // Note: we rebuild the platform outline on every test because the compiler
+    // currently mutates the in-memory representation of the program without
+    // cloning it.
+    return loadProgramFromBytes(outlineBytes);
+  }
+
+  static create(Map<String, String> environment) async {
+    environment[ENABLE_FULL_COMPILE] = "";
+    environment[AST_KIND_INDEX] = "${AstKind.Kernel.index}";
+    bool updateExpectations = environment["updateExpectations"] == "true";
+    Uri sdk = await computePatchedSdk();
+    Uri outlineUri = sdk.resolve('outline.dill');
+    Uri packages = Uri.base.resolve(".packages");
+    TranslateUri uriTranslator =
+        await TranslateUri.parse(PhysicalFileSystem.instance, packages);
+    List<int> outlineBytes = new File.fromUri(outlineUri).readAsBytesSync();
+    return new TreeShakerContext(
+        outlineUri, uriTranslator, outlineBytes, updateExpectations);
+  }
+}
+
+/// Step that extracts the test-specific options and builds the program without
+/// applying tree-shaking.
+class BuildProgram
+    extends Step<TestDescription, _IntermediateData, TreeShakerContext> {
+  const BuildProgram();
+  String get name => "build program";
+  Future<Result<_IntermediateData>> run(
+      TestDescription description, TreeShakerContext context) async {
+    try {
+      var platformOutline = context.loadPlatformOutline();
+      platformOutline.unbindCanonicalNames();
+      var dillTarget =
+          new DillTarget(new Ticker(isVerbose: false), context.uriTranslator);
+      dillTarget.loader.appendLibraries(platformOutline);
+      var sourceTarget = new KernelTarget(PhysicalFileSystem.instance,
+          dillTarget, context.uriTranslator, false);
+      await dillTarget.buildOutlines();
+
+      var inputUri = description.uri;
+
+      /// We treat the lib.dart library as a special dependency that was
+      /// previously built. To do so, we build it and append it back to the
+      /// dillTarget before building the actual test.
+      var libUri = inputUri.resolve('lib/lib.dart');
+      sourceTarget.read(libUri);
+      dillTarget.loader.appendLibraries(
+          await sourceTarget.buildOutlines(), (uri) => uri == libUri);
+
+      /// This new KernelTarget contains only sources from the test without
+      /// lib.dart.
+      sourceTarget = new KernelTarget(PhysicalFileSystem.instance, dillTarget,
+          context.uriTranslator, false);
+
+      await dillTarget.buildOutlines();
+      sourceTarget.read(inputUri);
+      var contents = new File.fromUri(inputUri).readAsStringSync();
+      var showCoreLibraries = contents.contains("@@SHOW_CORE_LIBRARIES@@");
+
+      await sourceTarget.buildOutlines();
+      // Note: We run the tree-shaker as a separate step on this suite to be
+      // able to specify what libraries to tree shake (by default only the code
+      // in the dillTarget gets tree-shaken). We could apply the tree-shaker
+      // twice, but that seems unnecessary.
+      var program = await sourceTarget.buildProgram(trimDependencies: true);
+      return pass(new _IntermediateData(inputUri, program, showCoreLibraries));
+    } on InputError catch (e, s) {
+      return fail(null, e.error, s);
+    }
+  }
+}
+
+/// Intermediate result from the testing chain.
+class _IntermediateData {
+  /// The input URI provided to the test.
+  final Uri uri;
+
+  /// Program built by [BuildProgram].
+  final Program program;
+
+  /// Whether the output should include tree-shaking information about the core
+  /// libraries. This is specified in a comment on individual test files where
+  /// we believe that information is relevant.
+  final bool showCoreLibraries;
+
+  _IntermediateData(this.uri, this.program, this.showCoreLibraries);
+}
+
+/// A step that runs the tree-shaker and checks againt an expectation file for
+/// the list of members and classes that should be preserved by the tree-shaker.
+class CheckShaker extends Step<_IntermediateData, String, ChainContext> {
+  final bool updateExpectations;
+  const CheckShaker({this.updateExpectations: false});
+
+  String get name => "match shaker expectation";
+
+  /// Tree-shake dart:* libraries and the library under [_specialLibraryPath].
+  bool _isTreeShaken(Uri uri) =>
+      uri.isScheme('dart') ||
+      Uri.base.resolveUri(uri).path.endsWith(_specialLibraryPath);
+
+  Future<Result<String>> run(
+      _IntermediateData data, ChainContext context) async {
+    String actualResult;
+    var entryUri = data.program.libraries
+        .firstWhere((l) => !l.importUri.isScheme('dart'))
+        .importUri;
+
+    var program = data.program;
+
+    var errors = verifyProgram(program, isOutline: false);
+    if (!errors.isEmpty) {
+      return new Result<String>(
+          null, context.expectationSet["VerificationError"], errors, null);
+    }
+
+    // Build a text representation of what we expect to be retained.
+    var buffer = new StringBuffer();
+    buffer.writeln('DO NOT EDIT -- this file is autogenerated ---');
+    buffer.writeln('Tree-shaker preserved the following:');
+    for (var library in program.libraries) {
+      var importUri = library.importUri;
+      if (!_isTreeShaken(importUri)) continue;
+      if (importUri.isScheme('dart') && !data.showCoreLibraries) continue;
+      String uri = relativizeUri(library.importUri);
+      buffer.writeln('\nlibrary $uri:');
+      for (var member in library.members) {
+        buffer.writeln('  - member ${member.name}');
+      }
+      for (var typedef_ in library.typedefs) {
+        buffer.writeln('  - typedef ${typedef_.name}');
+      }
+      for (var cls in library.classes) {
+        buffer.writeln('  - class ${cls.name}');
+        for (var member in cls.members) {
+          var name = '${member.name}';
+          if (name == "") {
+            buffer.writeln('    - (default constructor)');
+          } else {
+            buffer.writeln('    - $name');
+          }
+        }
+      }
+    }
+
+    actualResult = "$buffer";
+
+    // Compare against expectations using the text representation.
+    File expectedFile = new File("${entryUri.toFilePath()}.shaker");
+    if (await expectedFile.exists()) {
+      String expected = await expectedFile.readAsString();
+      if (expected.trim() != actualResult.trim()) {
+        if (!updateExpectations) {
+          String diff = await runDiff(expectedFile.uri, actualResult);
+          return fail(
+              null, "$entryUri doesn't match ${expectedFile.uri}\n$diff");
+        }
+      } else {
+        return pass(actualResult);
+      }
+    }
+    if (updateExpectations) {
+      expectedFile.writeAsStringSync(actualResult);
+      return pass(actualResult);
+    } else {
+      return fail(
+          actualResult,
+          """
+Please create file ${expectedFile.path} with this content:
+$buffer""");
+    }
+  }
+}
+
+/// A special library used only to test the shaker. The suite above will
+/// tree-shake the contents of this library.
+const _specialLibraryPath = 'pkg/front_end/testcases/shaker/lib/lib.dart';