Map merging.

pkg/analyzer/test/src/util/yaml_test.dart

+// Copyright (c) 2015, 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 analyzer.test.util.yaml;
+
+import 'package:analyzer/src/util/yaml.dart';
+import 'package:unittest/unittest.dart';
+
+import '../../utils.dart';
+
+main() {
+  initializeTestEnvironment();
+
+  group('yaml', () {
+    group('merge', () {
+      test('map', () {
+        expect(
+            merge({
+              'one': true,
+              'two': false,
+              'three': {
+                'nested': {'four': true}
+              }
+            }, {
+              'three': {
+                'nested': {'four': false, 'five': true},
+                'five': true
+              }

[Brian Wilkerson, 2015/11/03 01:07:27]

Add a sibling to "three" to ensure that unmatched keys from both sides are
retained.

[pquitslund, 2015/11/03 18:38:09]

Done.

+            }),
+            equals({
+              'one': true,
+              'two': false,
+              'three': {
+                'nested': {'four': false, 'five': true},

[Brian Wilkerson, 2015/11/03 01:07:27]

Can't actually tell whether the resulting value for "nested" is the result of a
merge or just the second value.

[pquitslund, 2015/11/03 18:38:08]

Fixed.

+                'five': true
+              }
+            }));
+      });
+
+      test('list', () {
+        expect(merge([1, 2, 3], [2, 3, 4, 5]), equals([1, 2, 3, 4, 5]));
+      });
+      test('list w/ promotion', () {
+        expect(merge(['one', 'two', 'three'], {'three': false, 'four': true}),
+            equals({'one': true, 'two': true, 'three': false, 'four': true}));
+        expect(merge({'one': false, 'two': false}, ['one', 'three']),
+            equals({'one': true, 'two': false, 'three': true}));
+      });
+      test('map w/ list promotion', () {
+        var map1 = {
+          'one': ['a', 'b', 'c']
+        };
+        var map2 = {
+          'one': {'a': true, 'b': false}
+        };
+        var map3 = {
+          'one': {'a': true, 'b': false, 'c': true}
+        };
+        expect(merge(map1, map2), map3);
+      });

[Brian Wilkerson, 2015/11/03 01:07:27]

Consider also testing
- merging maps and lists where the maps are not suitable for promotion, and
- merging two values that are neither maps nor lists.

[pquitslund, 2015/11/03 18:38:09]

Fantastic.  Thanks for the nudge.  It turns out my `is` check with reified types
was failing at runtime!  Specifically,

  {'foo': bar} is Map<Object,bool>

was evaluating to `true` which was NOT what I expected.

Cheers!

+    });
+  });
+}
+
+final Merger merger = new Merger();
+
+Object merge(Object o1, Object o2) => merger.merge(o1, o2);