feat(MapFormatter): Add MapFormatter.

MapFormatter can be used with repeat decorator to display a list of key value pairs

Closes dart-archive#394

lib/formatter/map.dart

@@ -0,0 +1,27 @@
+part of angular.formatter_internal;
+
+/**
+ * Returns a list of key-value pairs.
+ *
+ * Usage:
+ *
+ *     {{ {'key1': 'value1', 'key2':'value2'} | map }}
+ */
+@Formatter(name:'map')
+class MapFormatter<K, V> implements Function {
+  List<_KeyValue<K, V>> call(Map<K, V> inputMap) {
+    if (inputMap == null) return null;
+    List<_KeyValue<K, V>> result = [];
+    inputMap.keys.forEach((K k) {
+      result.add(new _KeyValue(k, inputMap[k]));
+    });
+    return result;
+  }
+}
+
+class _KeyValue<K, V> {
+  K key;
+  V value;
+
+  _KeyValue(this.key, this.value);
+}

lib/formatter/module.dart

@@ -29,6 +29,7 @@ export "package:angular/formatter/module_internal.dart" show
     Json,
     LimitTo,
     Lowercase,
+    MapFormatter,
     Number,
     OrderBy,
     Uppercase,

lib/formatter/module_internal.dart

@@ -13,6 +13,7 @@ part 'filter.dart';
 part 'json.dart';
 part 'limit_to.dart';
 part 'lowercase.dart';
+part 'map.dart';
 part 'number.dart';
 part 'order_by.dart';
 part 'uppercase.dart';
@@ -26,6 +27,7 @@ class FormatterModule extends Module {
     type(Json);
     type(LimitTo);
     type(Lowercase);
+    type(MapFormatter);
     type(Number);
     type(OrderBy);
     type(Uppercase);

test/angular_spec.dart

@@ -215,6 +215,7 @@ main() {
         "angular.formatter_internal.Json",
         "angular.formatter_internal.LimitTo",
         "angular.formatter_internal.Lowercase",
+        "angular.formatter_internal.MapFormatter",
         "angular.formatter_internal.Number",
         "angular.formatter_internal.OrderBy",
         "angular.formatter_internal.Stringify",

test/formatter/map_spec.dart

@@ -0,0 +1,15 @@
+library map_spec;
+
+import '../_specs.dart';
+import 'package:angular/formatter/module.dart';
+
+void main() {
+  describe('map', () {
+    it('should convert a map to list of key value pairs', inject((Parser parse, FormatterMap formatters) {
+      List result = parse('{"key1": "value1", "key2": "value2"} | map').eval(null, formatters);
+      expect(result.map((kv) => kv.key)).toEqual( ["key1", "key2"]);
+      expect(result.map((kv) => kv.value)).toEqual( ["value1", "value2"]);
+      expect(parse('null | map').eval(null, formatters)).toEqual(null);
+    }));
+  });
+}