Formatter selection preservation support.

pkg/analyzer_experimental/test/services/formatter_test.dart

 // Copyright (c) 2013, 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:unittest/unittest.dart';
 
 import 'package:analyzer_experimental/src/generated/scanner.dart';
 import 'package:analyzer_experimental/src/services/formatter_impl.dart';
 import 'package:analyzer_experimental/src/services/writer.dart';
 
@@ skipping 754 matching lines @@
     });
 
     test('initialIndent', () {
       var formatter = new CodeFormatter(
           new FormatterOptions(initialIndentationLevel: 2));
       var formattedSource = 
           formatter.format(CodeKind.STATEMENT, 'var x;').source;
       expect(formattedSource, startsWith('    '));
     });
 
+    test('selections', () {
+      expectSelectedPostFormat('class X {}', '}');
+      expectSelectedPostFormat('class X{}', '{');
+      expectSelectedPostFormat('class X{int y;}', ';');
+      expectSelectedPostFormat('class X{int y;}', '}');
+      expectSelectedPostFormat('class X {}', ' {');
+    });
+    
   });
 
 
   /// Token streams
   group('token streams', () {
 
     test('string tokens', () {
       expectTokenizedEqual('class A{}', 'class A{ }');
       expectTokenizedEqual('class A{}', 'class A{\n  }\n');
       expectTokenizedEqual('class A {}', 'class A{ }');
@@ skipping 163 matching lines @@
 Token closeParen(int offset) =>
     new StringToken(TokenType.CLOSE_PAREN, '}', offset);
 
 Token chain(List<Token> tokens) {
   for (var i = 0; i < tokens.length - 1; ++i) {
     tokens[i].setNext(tokens[i + 1]);
   }
   return tokens[0];
 }
 
-String formatCU(src, {options: const FormatterOptions()}) =>
-    new CodeFormatter(options).format(CodeKind.COMPILATION_UNIT, src).source;
+FormattedSource formatCU(src, {options: const FormatterOptions(), selection}) =>
+    new CodeFormatter(options).format(
+        CodeKind.COMPILATION_UNIT, src, selection: selection);
 
 String formatStatement(src, {options: const FormatterOptions()}) =>
     new CodeFormatter(options).format(CodeKind.STATEMENT, src).source;
 
 Token tokenize(String str) => new StringScanner(null, str, null).tokenize();
 
+expectSelectedPostFormat(src, token) {
+  var preOffset = src.indexOf(token);
+  var length = token.length;
+  var formatted = formatCU(src, selection: new Selection(preOffset, length));
+  var postOffset = formatted.selection.offset;
+  expect(formatted.source.substring(postOffset, postOffset + length),
+      equals(src.substring(preOffset, preOffset + length)));
+}
 
 expectTokenizedEqual(String s1, String s2) =>
     expectStreamsEqual(tokenize(s1), tokenize(s2));
 
 expectTokenizedNotEqual(String s1, String s2) =>
     expect(()=> expectStreamsEqual(tokenize(s1), tokenize(s2)),
     throwsA(new isInstanceOf<FormatterException>()));
 
 expectStreamsEqual(Token t1, Token t2) =>
     new TokenStreamComparator(null, t1, t2).verifyEquals();
 
 expectStreamsNotEqual(Token t1, Token t2) =>
     expect(() => new TokenStreamComparator(null, t1, t2).verifyEquals(),
     throwsA(new isInstanceOf<FormatterException>()));
 
-expectCUFormatsTo(src, expected) => expect(formatCU(src), equals(expected));
+expectCUFormatsTo(src, expected) => 
+    expect(formatCU(src).source, equals(expected));
 
-expectStmtFormatsTo(src, expected) => expect(formatStatement(src),
-    equals(expected));
+expectStmtFormatsTo(src, expected) => 
+    expect(formatStatement(src), equals(expected));