Enhance DirectiveListener to collect import/exports with combinators.

pkg/front_end/test/src/incremental/file_state_test.dart

 // 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 file.
 
 import 'package:front_end/memory_file_system.dart';
 import 'package:front_end/src/fasta/translate_uri.dart';
 import 'package:front_end/src/incremental/file_state.dart';
 import 'package:test/test.dart';
 import 'package:test_reflective_loader/test_reflective_loader.dart';
 
@@ skipping 51 matching lines @@
     expect(aFile.exportedLibraries, isEmpty);
     expect(aFile.partFiles, isEmpty);
 
     expect(bFile.fileUri, b);
     expect(bFile.exists, isTrue);
     _assertImportedUris(bFile, [_coreUri]);
     expect(bFile.exportedLibraries, isEmpty);
     expect(bFile.partFiles, isEmpty);
   }
 
+  test_getFile_exports() async {
+    var a = writeFile('/a.dart', '');
+    var b = writeFile('/b.dart', '');
+    var c = writeFile('/c.dart', '');
+    var d = writeFile(
+        '/d.dart',
+        r'''
+export "a.dart" show A, B;
+export "b.dart" hide C, D;
+export "c.dart" show A, B, C, D hide C show A, D;
+''');
+
+    FileState aFile = await fsState.getFile(a);
+    FileState bFile = await fsState.getFile(b);
+    FileState cFile = await fsState.getFile(c);
+    FileState dFile = await fsState.getFile(d);
+
+    expect(dFile.exports, hasLength(3));
+    {
+      NamespaceExport export_ = dFile.exports[0];
+      expect(export_.library, aFile);
+      expect(export_.combinators, hasLength(1));
+      expect(export_.combinators[0].isShow, isTrue);
+      expect(export_.combinators[0].names, unorderedEquals(['A', 'B']));
+      expect(export_.filter('A'), isTrue);
+      expect(export_.filter('B'), isTrue);
+      expect(export_.filter('C'), isFalse);
+      expect(export_.filter('D'), isFalse);
+    }
+    {
+      NamespaceExport export_ = dFile.exports[1];
+      expect(export_.library, bFile);
+      expect(export_.combinators, hasLength(1));
+      expect(export_.combinators[0].isShow, isFalse);
+      expect(export_.combinators[0].names, unorderedEquals(['C', 'D']));
+      expect(export_.filter('A'), isTrue);
+      expect(export_.filter('B'), isTrue);
+      expect(export_.filter('C'), isFalse);
+      expect(export_.filter('D'), isFalse);
+    }
+    {
+      NamespaceExport export_ = dFile.exports[2];
+      expect(export_.library, cFile);
+      expect(export_.combinators, hasLength(3));
+      expect(export_.combinators[0].isShow, isTrue);
+      expect(
+          export_.combinators[0].names, unorderedEquals(['A', 'B', 'C', 'D']));
+      expect(export_.combinators[1].isShow, isFalse);
+      expect(export_.combinators[1].names, unorderedEquals(['C']));
+      expect(export_.combinators[2].isShow, isTrue);
+      expect(export_.combinators[2].names, unorderedEquals(['A', 'D']));
+      expect(export_.filter('A'), isTrue);
+      expect(export_.filter('B'), isFalse);
+      expect(export_.filter('C'), isFalse);
+      expect(export_.filter('D'), isTrue);
+    }
+  }
+
   test_topologicalOrder_cycleBeforeTarget() async {
     var aUri = _writeFileDirectives('/a.dart');
     var bUri = _writeFileDirectives('/b.dart', imports: ['c.dart']);
     var cUri = _writeFileDirectives('/c.dart', imports: ['b.dart']);
     var dUri = _writeFileDirectives('/d.dart', imports: ['a.dart', 'b.dart']);
 
     FileState core = await fsState.getFile(_coreUri);
     FileState a = await fsState.getFile(aUri);
     FileState b = await fsState.getFile(bUri);
     FileState c = await fsState.getFile(cUri);
@@ skipping 64 matching lines @@
   Uri _writeFileDirectives(String path,
       {List<String> imports: const [], List<String> exports: const []}) {
     return writeFile(
         path,
         '''
 ${imports.map((uri) => 'import "$uri";').join('\n')}
 ${exports.map((uri) => 'export "$uri";').join('\n')}
 ''');
   }
 }