Analysis request `getReachableSources` (#24893).

pkg/analysis_server/test/services/dependencies/reachable_source_collector_test.dart

+// Copyright (c) 2015, 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.
+
+library test.services.dependencies.import_collector;
+
+import 'package:analysis_server/src/services/dependencies/reachable_source_collector.dart';
+import 'package:analyzer/src/generated/ast.dart';
+import 'package:analyzer/src/generated/source.dart';
+import 'package:test_reflective_loader/test_reflective_loader.dart';
+import 'package:unittest/unittest.dart';
+
+import '../../abstract_context.dart';
+import '../../utils.dart';
+
+main() {
+  initializeTestEnvironment();
+  defineReflectiveTests(ReachableSourceCollectorTest);
+}
+
+@reflectiveTest
+class ReachableSourceCollectorTest extends AbstractContextTest {
+  CompilationUnit addLibrary(String path, String contents) =>
+      resolveLibraryUnit(addSource(path, contents));
+
+  Map<String, List<String>> importsFor(Source source) =>
+      new ReachableSourceCollector(source, context).collectSources();
+
+  test_sources() {
+    Source lib1 = addSource(
+        '/lib1.dart',
+        '''
+import "lib2.dart";
+import "dart:html";''');
+    Source lib2 = addSource('/lib2.dart', 'import "lib1.dart";');
+
+    Source lib3 = addSource('/lib3.dart', 'import "lib4.dart";');
+    addSource('/lib4.dart', 'import "lib3.dart";');
+
+    Map<String, List<String>> imports = importsFor(lib1);
+
+    // Verify keys.
+    expect(
+        imports.keys,
+        unorderedEquals([
+          'dart:_internal',
+          'dart:async',
+          'dart:core',
+          'dart:html',
+          'dart:math',
+          'file:///lib1.dart',
+          'file:///lib2.dart',
+        ]));
+    // Values.
+    expect(imports['file:///lib1.dart'],
+        unorderedEquals(['dart:core', 'dart:html', 'file:///lib2.dart']));
+
+    // Check transitivity.
+    expect(importsFor(lib2).keys, contains('dart:html'));
+
+    // Cycles should be OK.
+    expect(
+        importsFor(lib3).keys,
+        unorderedEquals([
+          'dart:_internal',
+          'dart:async',
+          'dart:core',
+          'dart:math',
+          'file:///lib3.dart',
+          'file:///lib4.dart'
+        ]));
+  }
+
+  test_null_context() {
+    Source lib = addSource('/lib.dart', '');
+    // Shouldn't throw an exception.
+    expect(new ReachableSourceCollector(lib, null).collectSources(), isEmpty);
+  }
+
+  test_null_source() {
+    // Shouldn't throw an exception.
+    expect(
+        new ReachableSourceCollector(null, context).collectSources(), isEmpty);
+  }
+}