Optimize paths comparision in source closure sorting.

pkg/analyzer/test/src/summary/incremental_cache_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 'package:analyzer/dart/element/element.dart';
 import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/summary/incremental_cache.dart';
 import 'package:unittest/unittest.dart';
 
 import '../../generated/test_support.dart';
 import '../../reflective_tests.dart';
 import '../abstract_single_unit.dart';
 
 main() {
   groupSep = ' | ';
+  runReflectiveTests(ComparePathsTest);
   runReflectiveTests(IncrementalCacheTest);
 }
 
+@reflectiveTest
+class ComparePathsTest extends AbstractSingleUnitTest {
+  void test_empty() {
+    expect(comparePaths('', ''), 0);
+  }
+
+  void test_equal() {
+    expect(comparePaths('abc', 'abc'), 0);
+  }
+
+  void test_longer_suffixAfter() {
+    expect(comparePaths('aab', 'aa'), 1);
+  }
+
+  void test_longer_suffixBefore() {
+    expect(comparePaths('aaa', 'ab'), -1);
+  }
+
+  void test_longer_suffixSame() {
+    expect(comparePaths('aaa', 'aa'), 1);
+  }
+
+  void test_sameLength_before0() {
+    expect(comparePaths('aaa', 'bbb'), -1);
+  }
+
+  void test_sameLength_before1() {
+    expect(comparePaths('aaa', 'bba'), -1);
+  }
+
+  void test_sameLength_before2() {
+    expect(comparePaths('aaa', 'bba'), -1);
+  }
+
+  void test_shorter_suffixAfter() {
+    expect(comparePaths('ab', 'aaa'), 1);
+  }
+
+  void test_shorter_suffixBefore() {
+    expect(comparePaths('aa', 'aab'), -1);
+  }
+
+  void test_shorter_suffixSame() {
+    expect(comparePaths('aa', 'aaa'), -1);
+  }
+}
+
 /**
  * TODO(scheglov) write more tests for invalidation.
  */
 @reflectiveTest
 class IncrementalCacheTest extends AbstractSingleUnitTest {
   _TestCacheStorage storage = new _TestCacheStorage();
   IncrementalCache cache;
 
   Source putLibrary(String path, String code) {
     Source source = addSource(path, code);
@@ skipping 207 matching lines @@
   @override
   List<int> get(String key) {
     return map[key];
   }
 
   @override
   void put(String key, List<int> bytes) {
     map[key] = bytes;
   }
 }