feat(filters): add filters in support of pure fields and methods, and to observe lists and maps

Closes dart-archive#359, dart-archive#394, dart-archive#397, dart-archive#757.

Relates to dart-archive#772, dart-archive#773.

Author: chalin

lib/filter/module.dart

@@ -1,6 +1,7 @@
 library angular.filter;
 
 import 'dart:convert' show JSON;
+import 'dart:mirrors';
 import 'package:intl/intl.dart';
 import 'package:di/di.dart';
 import 'package:angular/core/module.dart';
@@ -15,6 +16,7 @@ part 'lowercase.dart';
 part 'number.dart';
 part 'order_by.dart';
 part 'uppercase.dart';
+part 'pure.dart';
 
 class NgFilterModule extends Module {
   NgFilterModule() {
@@ -27,5 +29,8 @@ class NgFilterModule extends Module {
     type(NumberFilter);
     type(OrderByFilter);
     type(UppercaseFilter);
+    type(ObserveFilter);
+    type(GetPureFieldFilter);
+    type(ApplyPureMethodFilter);
   }
 }

lib/filter/pure.dart

@@ -0,0 +1,64 @@
+part of angular.filter;
+
+/**
+ * This filter returns its argument unchanged but, for `List` and `Map` 
+ * arguments, it causes the argument contents to be observed (as opposed to
+ * only its identity).
+ *
+ * Example:
+ *
+ *     {{ list | observe }}
+ */
+@NgFilter(name: 'observe')
+class ObserveFilter implements Function {
+  dynamic call(dynamic _) => _;
+}
+
+/**
+ * This filter returns the argument's value of the named field. Use this only 
+ * when the field get operation is known to be pure (side-effect free).
+ *
+ * Examples:
+ *
+ *     {{  map | field:'keys' }}
+ *     {{  map | field:'values' }}
+ *     {{ list | field:'reversed' }}
+ */
+@NgFilter(name: 'field')
+class GetPureFieldFilter implements Function {
+  dynamic call(Object o, String fieldName) =>
+      o == null ? null :
+        reflect(o).getField(new Symbol(fieldName)).reflectee;
+}
+
+/**
+ * This filter returns the result of invoking the named method on the filter 
+ * argument. Use this only when the method is known to be pure (side-effect free).
+ *
+ * Examples:
+ *
+ *     <span>{{ expression | method:'toString' }}</span>
+ *     <ul><li ng-repeat="n in (names | method:'split':[','])">{{n}}</li></ul>
+ * 
+ * The first example is useful when _expression_ yields a new identity but its
+ * string rendering is unchanged.
+ */
+@NgFilter(name: 'method')
+class ApplyPureMethodFilter implements Function {
+  dynamic call(Object o, String methodName, [args, Map<String,dynamic> namedArgs]) {
+    if (o == null) return null;
+        
+    if (args is Map) {
+      namedArgs = args;
+      args = const [];
+    } else if (args == null) {
+      args = const [];
+    }
+    final Map<Symbol,dynamic> _namedArgs = namedArgs == null ?
+        const <Symbol,dynamic>{} : <Symbol,dynamic>{};
+    if (namedArgs != null) {
+      namedArgs.forEach((k,v) => _namedArgs[new Symbol(k)] = v);
+    }
+    return reflect(o).invoke(new Symbol(methodName), args, _namedArgs).reflectee;
+  }
+}

test/core/scope_spec.dart

@@ -150,7 +150,6 @@ void main() {
         expect(logger).toEqual([]);
       });
 
-
       it('should prefix', (Logger logger, Map context, RootScope rootScope) {
         context['a'] = true;
         rootScope.watch('!a', (value, previous) => logger(value));
@@ -228,7 +227,21 @@ void main() {
         expect(logger).toEqual(['identity', 'keys', ['foo', 'bar']]);
         logger.clear();
       });
-
+      
+      it('should watch list value (vs. identity) changes when "observe" filter is used', 
+          (Logger logger, Map context, RootScope rootScope, AstParser parser,
+              FilterMap filters) {
+        final list = [true, 2, 'abc'];
+        final logVal = (value, _) => logger(value);
+        context['list'] = list;
+        rootScope.watch( parser('list | observe', filters: filters), logVal);
+        rootScope.digest();
+        expect(logger).toEqual([list]);
+        logger.clear();
+        context['list'][2] = 'def';
+        rootScope.digest();
+        expect(logger).toEqual([[true, 2, 'def']]);
+      });
     });
 
 

test/filter/pure_spec.dart

@@ -0,0 +1,49 @@
+library pure_spec;
+
+import '../_specs.dart';
+
+void main() {
+  describe('pure filters', () {
+    beforeEach((Scope scope, Parser parse, FilterMap filters) {
+      scope.context['string'] = 'abc';
+      scope.context['list'] = 'abc'.split('');
+      scope.context['map'] = { 'a': 1, 'b': 2, 'c': 3 };
+    });
+
+    // Note that the `observe` filter is tested in [scope_spec.dart].
+
+    it('should return the value of the named field', 
+        (Scope scope, Parser parse, FilterMap filters) {
+      expect(parse("list | field:'reversed'").eval(scope.context, filters)
+          ).toEqual(['c', 'b', 'a']);
+      expect(parse("map | field:'keys'").eval(scope.context, filters)).toEqual(
+          ['a', 'b', 'c']);
+      expect(parse("map | field:'values'").eval(scope.context, filters)
+          ).toEqual([1, 2, 3]);
+    });
+
+    it('should return method call result', 
+        (Scope scope, Parser parse, FilterMap filters) {
+      expect(parse("list | method:'toString'").eval(scope.context, filters)
+          ).toEqual('[a, b, c]');
+      expect(parse("list | method:'join':['']").eval(scope.context, filters)
+          ).toEqual('abc');
+      expect(parse("string | method:'split':['']").eval(scope.context, filters)
+          ).toEqual(['a', 'b', 'c']);
+    });
+
+    it('should return method call result using namedArgs', 
+        (Scope scope, Parser parse, FilterMap filters) {
+      scope.context['isB'] = (s) => s == 'b';
+      scope.context['zero'] = () => 0;
+
+      // Test for no positional args but with named args.
+      expect(parse("list | method:'toList':{'growable':false}").eval(
+          scope.context, filters)).toEqual(['a', 'b', 'c']);
+
+      // Test for both positional and named args.
+      expect(parse("list | method:'firstWhere':[isB]:{'orElse':zero}").eval(
+          scope.context, filters)).toEqual('b');
+    });
+  });
+}