Add a friendly error message for using a tab as indentation.

utils/tests/pub/yaml_test.dart

 // Copyright (c) 2012, 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('yaml_test');
 
 #import('dart:math');
 
 #import('../../../pkg/unittest/unittest.dart');
 #import('../../pub/yaml/yaml.dart');
@@ skipping 52 matching lines @@
       Expect.equals('baz', normalMap[yamlMap({'foo': 'bar'})]);
     });
 
     test('treats YamlMap keys the same as normal maps', () {
       var map = yamlMap();
       map[{'a': 'b'}] = 5;
       Expect.equals(5, map[yamlMap({'a': 'b'})]);
     });
   });
 
+  group('has a friendly error message for', () {
+    test('using a tab as indentation', () {
+      Expect.throws(() => loadYaml('foo:\n\tbar'),

[Bob Nystrom, 2012/08/30 16:43:51]

expect(() => loadYaml('foo:\n\tbar'),
    throwsA(contains('\\t is not allowed as indentation'));

[nweiz, 2012/08/30 19:19:02]

Done, although just "contains()" doesn't work here, since we're matching against
an exception rather than a string.

+          (e) => e.toString().contains('\\t is not allowed as indentation'));
+    });
+
+    test('using a tab not as indentation', () {
+      Expect.throws(() => loadYaml('''
+          "foo
+          \tbar"
+          error'''),
+        (e) => !e.toString().contains('\\t is not allowed as indentation'));

[Bob Nystrom, 2012/08/30 16:43:51]

Ditto.

We're trying to phase out all uses of Expect and eventually eliminate it from
corelib.

[nweiz, 2012/08/30 19:19:02]

Done.

+    });
+  });
+
   // The following tests are all taken directly from the YAML spec
   // (http://www.yaml.org/spec/1.2/spec.html). Most of them are code examples
   // that are directly included in the spec, but additional tests are derived
   // from the prose.
 
   // A few examples from the spec are deliberately excluded, because they test
   // features that this implementation doesn't intend to support (character
   // encoding detection and user-defined tags). More tests are commented out,
   // because they're intended to be supported but not yet implemented.
 
@@ skipping 1773 matching lines @@
         A null: null
         Also a null: # Empty
         Not a null: ""
         Booleans: [ true, True, false, FALSE ]
         Integers: [ 0, 0o7, 0x3A, -19 ]
         Floats: [ 0., -0.0, .5, +12e03, -2E+05 ]
         Also floats: [ .inf, -.Inf, +.INF, .NAN ]''');
     });
   });
 }