Avoid printing braces for one-statement blocks in js-printer.

tests/compiler/dart2js/js_parser_statements_test.dart

 // Copyright (c) 2014, 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:expect/expect.dart';
 import 'package:async_helper/async_helper.dart';
 import 'mock_compiler.dart';
 import 'package:compiler/src/js/js.dart' as jsAst;
 import 'package:compiler/src/js/js.dart' show js;
@@ skipping 115 matching lines @@
     testStatement('if (#a) #b;',
                   {'a': false, 'b': block12},
                   ';'),
     testStatement('if (#a) 3; else #b;',
                   {'a': true, 'b': block12},
                   '3;'),
     testStatement('if (#a) 3; else #b;',
                   {'a': false, 'b': block12},
                   '{\n  1;\n  2;\n}'),
 
+
     testStatement('while (#) #', [eOne, block12], 'while (1) {\n  1;\n  2;\n}'),
     testStatement('while (#) #;', [eTrue, block12],
         'while (true) {\n  1;\n  2;\n}'),
     testStatement('while (#) #;', [eVar, block12],
         'while (x) {\n  1;\n  2;\n}'),
     testStatement('while (#) #;', ['a', block12],
         'while (a) {\n  1;\n  2;\n}'),
     testStatement('while (#) #;', ['a', stm],
         'while (a)\n  foo();'),
 
-    testStatement(
-        'do { {print(1);} do while(true); while (false) } while ( true )', [],
-        '''
+  testStatement(
+      'do { {print(1);} do while(true); while (false) } while ( true )', [],
+      '''
 do {
   print(1);
   do
     while (true)
       ;
   while (false);
 } while (true);
 '''),
     testStatement('do #; while ( # )', [block12, eOne],
         'do {\n  1;\n  2;\n} while (1); '),
@@ skipping 157 matching lines @@
     // Use the same name several times.
     testStatement('#a.prototype.#a = function(#b) { return #c.#c };',
                   {'a': 'name1_2',
                    'b': ['r', 'y'],
                    'c': 'name4_5'},
                   'name1_2.prototype.name1_2 = function(r, y) {\n'
                   '  return name4_5.name4_5;\n'
                   '};'),
 
     testStatement('label: while (a) { label2: break label;}', [],
-        'label:\n  while (a) {\n    label2:\n      break label;\n  }'),
+        'label:\n  while (a)\n    label2:\n      break label;\n  '),
 
 
     testStatement('var # = 3', ['x'], 'var x = 3;'),
     testStatement('var # = 3',
                   [new jsAst.VariableDeclaration('x')],
                   'var x = 3;'),
     testStatement('var # = 3, # = #',
                   ['x', 'y', js.number(2)],
                   'var x = 3, y = 2;'),
     testStatement('var #a = 3, #b = #c',
         {"a": 'x', "b": 'y', "c": js.number(2)},
                   'var x = 3, y = 2;'),
     testStatement('function #() {}', ['x'], 'function x() {\n}'),
     testStatement('function #() {}',
                   [new jsAst.VariableDeclaration('x')],
                   'function x() {\n}'),
     testStatement('try {} catch (#) {}', ['x'], 'try {\n} catch (x) {\n}'),
     testStatement('try {} catch (#a) {}', {"a": 'x'}, 'try {\n} catch (x) {\n}'),
     testStatement('try {} catch (#a) {}',
                   {"a": new jsAst.VariableDeclaration('x')},
                   'try {\n} catch (x) {\n}'),
+
+    // Test that braces around a single-statement block are removed by printer.
+    testStatement('while (a) {foo()}', [],
+        'while (a)\n  foo();'),
+    testStatement('if (a) {foo();}', [],
+        'if (a)\n  foo();'),
+    testStatement('if (a) {foo();} else {foo2();}', [],
+        'if (a)\n  foo();\nelse\n  foo2();'),
+    testStatement('if (a) foo(); else {foo2();}', [],
+        'if (a)\n  foo();\nelse\n  foo2();'),
+    testStatement('do {foo();} while(a);', [],
+        'do\n  foo();\nwhile (a);'),
+    testStatement('label: {foo();}', [],
+        'label:\n  foo();'),
+    testStatement('for (var key in a) {foo();}', [],
+        'for (var key in a)\n  foo();'),
+    // `label: break label;` gives problems on IE. Test that it is avoided.
+    testStatement('label: {break label;}', [],
+        'label: {\n  break label;\n}'),
+    // This works on IE:
+    testStatement('label: {label2: {break label;}}', [],
+        'label:\n  label2:\n    break label;\n'),
+    // Test dangling else:
+    testStatement('if (a) {if (b) {foo1();}} else {foo2();}', [], """
+if (a) {
+  if (b)
+    foo1();
+} else
+  foo2();"""),
+    testStatement('if (a) {if (b) {foo1();} else {foo2();}}', [], """
+if (a)
+  if (b)
+    foo1();
+  else
+    foo2();
+"""),
+    testStatement('if (a) {if (b) {foo1();} else {foo2();}} else {foo3();}',
+        [], """
+if (a)
+  if (b)
+    foo1();
+  else
+    foo2();
+else
+  foo3();"""),
+    testStatement('if (a) {while (true) if (b) {foo1();}} else {foo2();}',
+        [], """
+if (a) {
+  while (true)
+    if (b)
+      foo1();
+} else
+  foo2();"""),
   ]));
 }