Implement a front end API for querying the dependency structure of a project.

pkg/front_end/test/dependency_grapher_test.dart

+// Copyright (c) 2016, 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 file.
+
+import 'dart:async';
+
+import 'package:front_end/compiler_options.dart';
+import 'package:front_end/dependency_grapher.dart';
+import 'package:front_end/memory_file_system.dart';
+import 'package:path/path.dart' as pathos;
+import 'package:test/test.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+
+main() {
+  defineReflectiveSuite(() {
+    defineReflectiveTests(DependencyGrapherTest);
+  });
+}
+
+@reflectiveTest
+class DependencyGrapherTest {
+  LibraryNode checkLibrary(LibraryCycleNode cycle, String uri,
+      {List<String> dependencies: const [], List<String> parts: const []}) {
+    var library = cycle.libraries[Uri.parse(uri)];
+    expect(library.uri.toString(), uri);

[Siggi Cherem (dart-lang), 2016/12/15 23:51:33]

style nit: I prefer '${library.uri}'

It's shorter and more easily recognizable that it is a string.

Same thing below:
(dep) => '${dep.uri}'
(part) => '$part'

[Paul Berry, 2016/12/16 02:46:45]

Done.

+    expect(library.dependencies.map((dep) => dep.uri.toString()).toList(),
+        unorderedEquals(dependencies));
+    expect(
+        library.parts.map((part) => part.toString()), unorderedEquals(parts));

[Siggi Cherem (dart-lang), 2016/12/15 23:51:33]

is .toList needed here (or not needed above?) 

[Paul Berry, 2016/12/16 02:46:45]

Not needed above.  Good catch.

+    return library;
+  }
+
+  Future<List<LibraryCycleNode>> getCycles(Map<String, String> contents,
+      [List<String> startingPoints]) async {
+    // If no starting points given, assume the first entry in [contents] is the
+    // single starting point.
+    startingPoints ??= [contents.keys.first];
+    var fileSystem = new MemoryFileSystem(pathos.posix, '/');
+    contents.forEach((path, text) {
+      fileSystem.entityForPath(path).writeAsStringSync(text);
+    });
+    // TODO(paulberry): implement and test other option possibilities.
+    var options = new CompilerOptions()
+      ..fileSystem = fileSystem
+      ..chaseDependencies = true;
+    var graph = await graphForProgram(
+        startingPoints.map(pathos.posix.toUri).toList(), options);
+    return graph.topologicallySortedCycles;
+  }
+
+  /// Sort the given library cycles into a deterministic order based on their
+  /// URIs for easier unit testing.
+  List<LibraryCycleNode> sortCycles(Iterable<LibraryCycleNode> cycles) {
+    var result = cycles.toList();
+    String sortKey(LibraryCycleNode node) => node.libraries.keys.join(',');
+    result.sort((a, b) => Comparable.compare(sortKey(a), sortKey(b)));
+    return result;
+  }
+
+  test_exportDependency() async {
+    var cycles =
+        await getCycles({'/foo.dart': 'export "bar.dart";', '/bar.dart': ''});
+    expect(cycles, hasLength(2));
+    expect(cycles[0].libraries, hasLength(1));
+    checkLibrary(cycles[0], 'file:///bar.dart');
+    expect(cycles[1].libraries, hasLength(1));
+    checkLibrary(cycles[1], 'file:///foo.dart',
+        dependencies: ['file:///bar.dart']);
+  }
+
+  test_importDependency() async {
+    var cycles =
+        await getCycles({'/foo.dart': 'import "bar.dart";', '/bar.dart': ''});
+    expect(cycles, hasLength(2));
+    expect(cycles[0].libraries, hasLength(1));
+    checkLibrary(cycles[0], 'file:///bar.dart');
+    expect(cycles[1].libraries, hasLength(1));
+    checkLibrary(cycles[1], 'file:///foo.dart',
+        dependencies: ['file:///bar.dart']);
+  }
+
+  test_multipleStartingPoints() async {
+    var cycles = await getCycles({
+      '/a.dart': 'import "c.dart";',
+      '/b.dart': 'import "c.dart";',
+      '/c.dart': ''
+    }, [
+      '/a.dart',
+      '/b.dart'
+    ]);
+    expect(cycles, hasLength(3));
+    expect(cycles[0].libraries, hasLength(1));
+    checkLibrary(cycles[0], 'file:///c.dart');
+    // The other two cycles might be in any order, so sort them for
+    // reproducibility.
+    List<LibraryCycleNode> otherCycles = sortCycles(cycles.sublist(1));
+    checkLibrary(otherCycles[0], 'file:///a.dart',
+        dependencies: ['file:///c.dart']);
+    checkLibrary(otherCycles[1], 'file:///b.dart',
+        dependencies: ['file:///c.dart']);
+  }
+
+  test_parts() async {
+    var cycles = await getCycles({
+      '/foo.dart': 'library foo; part "a.dart"; part "b.dart";',
+      '/a.dart': 'part of foo;',
+      '/b.dart': 'part of foo;'
+    });
+    expect(cycles, hasLength(1));
+    expect(cycles[0].libraries, hasLength(1));
+    checkLibrary(cycles[0], 'file:///foo.dart',
+        parts: ['file:///a.dart', 'file:///b.dart']);
+  }
+
+  test_relativeUris() async {
+    var cycles = await getCycles({
+      '/a.dart': 'import "b/c.dart";',
+      '/b/c.dart': 'import "d/e.dart";',
+      '/b/d/e.dart': 'import "../f.dart";',
+      '/b/f.dart': ''
+    });
+    expect(cycles, hasLength(4));
+    expect(cycles[0].libraries, hasLength(1));
+    checkLibrary(cycles[0], 'file:///b/f.dart');
+    expect(cycles[1].libraries, hasLength(1));
+    checkLibrary(cycles[1], 'file:///b/d/e.dart',
+        dependencies: ['file:///b/f.dart']);
+    expect(cycles[2].libraries, hasLength(1));
+    checkLibrary(cycles[2], 'file:///b/c.dart',
+        dependencies: ['file:///b/d/e.dart']);
+    expect(cycles[3].libraries, hasLength(1));
+    checkLibrary(cycles[3], 'file:///a.dart',
+        dependencies: ['file:///b/c.dart']);
+  }
+
+  test_simpleCycle() async {
+    var cycles = await getCycles(
+        {'/foo.dart': 'import "bar.dart";', '/bar.dart': 'import "foo.dart";'});
+    expect(cycles, hasLength(1));
+    expect(cycles[0].libraries, hasLength(2));
+    var foo = checkLibrary(cycles[0], 'file:///foo.dart',
+        dependencies: ['file:///bar.dart']);
+    var bar = checkLibrary(cycles[0], 'file:///bar.dart',
+        dependencies: ['file:///foo.dart']);
+    expect(foo.dependencies[0], same(bar));
+    expect(bar.dependencies[0], same(foo));
+  }
+
+  test_singleFile() async {
+    var cycles = await getCycles({'/foo.dart': ''});
+    expect(cycles, hasLength(1));
+    expect(cycles[0].libraries, hasLength(1));
+    checkLibrary(cycles[0], 'file:///foo.dart');
+  }
+}