fix(parser): Allow access to Map properties in expressions

E.g. `map.keys`, `map.length`, etc. This is a proposed solution to dart-archive#394.

Author: chalin

bin/parser_generator_for_spec.dart

@@ -101,6 +101,11 @@ main(arguments) {
       'items[1].name',
       'list[3] = 2',
       'map["square"] = 6',
+      'map.isEmpty',
+      'map.isNotEmpty',
+      'map.keys',
+      'map.length',
+      'map.values',
       'method',
       'method()',
       'notAFn()',

lib/core/parser/eval_access.dart

@@ -80,7 +80,7 @@ abstract class AccessReflective {
     if (holder == null) {
       _cachedKind = CACHED_VALUE;
       return _cachedValue = null;
-    } else if (holder is Map) {
+    } else if (holder is Map && !isMapProperty(name)) {
       _cachedKind = CACHED_MAP;
       _cachedValue = null;
       return holder[name];
@@ -204,7 +204,7 @@ abstract class AccessFast {
 
   _eval(holder) {
     if (holder == null) return null;
-    return (holder is Map) ? holder[name] : getter(holder);
+    return (holder is Map && !isMapProperty(name)) ? holder[name] : getter(holder);
   }
 
   _assign(scope, holder, value) {

lib/core/parser/utils.dart

@@ -96,3 +96,13 @@ setKeyed(object, key, value) {
   }
   return value;
 }
+
+final List<String> _MAP_PROPERTIES = const <String>[
+  "hashCode", // any reason to exclude this?
+  "isEmpty",
+  "isNotEmpty",
+  "keys",
+  "length",
+  "runtimeType", // any reason to exclude this?
+  "values"];
+bool isMapProperty(String key) => _MAP_PROPERTIES.contains(key);

lib/tools/parser_generator/dart_code_gen.dart

@@ -2,6 +2,7 @@ library dart_code_gen;
 
 import 'package:angular/tools/reserved_dart_keywords.dart';
 import 'package:angular/core/parser/syntax.dart';
+import 'package:angular/core/parser/utils.dart';
 
 escape(String s) => s.replaceAllMapped(new RegExp(r'(\"|\$|\n)'), (m) {
   var char = m[1];
@@ -11,7 +12,7 @@ escape(String s) => s.replaceAllMapped(new RegExp(r'(\"|\$|\n)'), (m) {
 
 class DartCodeGen {
   final HelperMap getters = new HelperMap('_',
-      getterTemplate, getterTemplateForReserved);
+      getterTemplate, getterTemplateForReserved, getterTemplateWithoutMapTest);
   final HelperMap holders = new HelperMap('_ensure\$',
       holderTemplate, holderTemplateForReserved);
   final HelperMap setters = new HelperMap('_set\$',
@@ -223,14 +224,17 @@ class HelperMap {
   final String prefix;
   final Function template;
   final Function templateForReserved;
+  final Function templateWithoutMapTest;
 
-  HelperMap(this.prefix, this.template, this.templateForReserved);
+  HelperMap(this.prefix, this.template, this.templateForReserved, [this.templateWithoutMapTest]);
 
   String lookup(String key) {
     String name = _computeName(key);
     if (helpers.containsKey(key)) return name;
     helpers[key] = isReserved(key)
         ? templateForReserved(name, key)
+        : isMapProperty(key) && templateWithoutMapTest != null
+          ? templateWithoutMapTest(name, key)
         : template(name, key);
     return name;
   }
@@ -261,6 +265,9 @@ $name(o) {
 }
 """;
 
+String getterTemplateWithoutMapTest(String name, String key) => """
+$name(o) => o == null ? null : o.$key;
+""";
 
 // ------------------------------------------------------------------
 // Templates for generated holders (getters for assignment).

test/core/parser/parser_spec.dart

@@ -647,6 +647,16 @@ main() {
       });
 
 
+      it('should evaluate map item and field access', () {
+        context['map'] = { 'a': 1.1, 'b': 'B' };
+        expect(eval("map.isEmpty")).toEqual(false);
+        expect(eval("map.isNotEmpty")).toEqual(true);
+        expect(eval("map.keys")).toEqual(['a', 'b']);
+        expect(eval("map.length")).toEqual(2);
+        expect(eval("map.values")).toEqual([1.1, 'B']);
+      });
+
+
       it('should evaluate JSON', () {
         expect(eval("[{}]")).toEqual([{}]);
         expect(eval("[{a:[]}, {b:1}]")).toEqual([{"a":[]},{"b":1}]);