Make the JSON decoder (parser) create Dart maps lazily

tests/corelib/json_map_test.dart

+// Copyright (c) 2011, 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 json_map_test;
+
+import "package:expect/expect.dart";
+import 'dart:convert' show JSON;
+import 'dart:collection' show LinkedHashMap, HashMap;
+
+Map jsonify(Map map) => JSON.decode(JSON.encode(map));
+
+List listEach(Map map) {
+  var result = [];
+  map.forEach((String key, value) {
+    result.add(key);
+    result.add(value);
+  });
+  return result;
+}
+
+void main() {
+  testEmpty(jsonify({}));
+  testAtoB(jsonify({'a': 'b'}));
+
+  Map map = jsonify({});
+  map['a'] = 'b';
+  testAtoB(map);
+
+  map = jsonify({});
+  Expect.equals('b', map.putIfAbsent('a', () => 'b'));
+  testAtoB(map);
+
+  map = jsonify({});
+  map.addAll({'a': 'b'});
+  testAtoB(map);
+
+  testOrder(['a', 'b', 'c', 'd', 'e', 'f']);
+
+  testProto();
+  testToString();
+  testConcurrentModifications();
+  testType();
+  testNonStringKeys();
+  testClear();
+
+  testListEntry();
+}
+
+void testEmpty(Map map) {
+  for (int i = 0; i < 2; i++) {
+    Expect.equals(0, map.length);
+    Expect.isTrue(map.isEmpty);
+    Expect.isFalse(map.isNotEmpty);
+    Expect.listEquals([], map.keys.toList());
+    Expect.listEquals([], map.values.toList());
+    Expect.isNull(map['a']);
+    Expect.listEquals([], listEach(map));
+    Expect.isFalse(map.containsKey('a'));
+    Expect.isFalse(map.containsValue('a'));
+    Expect.isNull(map.remove('a'));
+    testLookupNonExistingKeys(map);
+    testLookupNonExistingValues(map);
+    map.clear();
+  }
+}
+
+void testAtoB(Map map) {
+  Expect.equals(1, map.length);
+  Expect.isFalse(map.isEmpty);
+  Expect.isTrue(map.isNotEmpty);
+  Expect.listEquals(['a'], map.keys.toList());
+  Expect.listEquals(['b'], map.values.toList());
+  Expect.equals('b', map['a']);
+  Expect.listEquals(['a', 'b'], listEach(map));
+  Expect.isTrue(map.containsKey('a'));
+  Expect.isFalse(map.containsKey('b'));
+  Expect.isTrue(map.containsValue('b'));
+  Expect.isFalse(map.containsValue('a'));
+
+  testLookupNonExistingKeys(map);
+  testLookupNonExistingValues(map);
+  Expect.equals('b', map.remove('a'));
+  Expect.isNull(map.remove('b'));
+  testLookupNonExistingKeys(map);
+  testLookupNonExistingValues(map);
+
+  map.clear();
+  testEmpty(map);
+}
+
+void testLookupNonExistingKeys(Map map) {
+  for (String key in ['__proto__', 'null', null]) {
+    Expect.isNull(map[key]);
+    Expect.isFalse(map.containsKey(key));
+  }
+}
+
+void testLookupNonExistingValues(Map map) {
+  for (var value in ['__proto__', 'null', null]) {
+    Expect.isFalse(map.containsValue(value));
+  }
+}
+
+void testOrder(List list) {
+  if (list.isEmpty) return;
+  else testOrder(list.skip(1).toList());
+
+  Map original = {};
+  for (int i = 0; i < list.length; i++) {
+    original[list[i]] = i;
+  }
+
+  Map map = jsonify(original);
+  Expect.equals(list.length, map.length);
+  Expect.listEquals(list, map.keys.toList());
+
+  for (int i = 0; i < 10; i++) {
+    map["$i"] = i;
+    Expect.equals(list.length + i + 1, map.length);
+    Expect.listEquals(list, map.keys.take(list.length).toList());
+  }
+}
+
+void testProto() {
+  Map map = jsonify({'__proto__': 0});
+  Expect.equals(1, map.length);
+  Expect.isTrue(map.containsKey('__proto__'));
+  Expect.listEquals(['__proto__'], map.keys.toList());
+  Expect.equals(0, map['__proto__']);
+  Expect.equals(0, map.remove('__proto__'));
+  testEmpty(map);
+
+  map = jsonify({'__proto__': null});
+  Expect.equals(1, map.length);
+  Expect.isTrue(map.containsKey('__proto__'));
+  Expect.listEquals(['__proto__'], map.keys.toList());
+  Expect.isNull(map['__proto__']);
+  Expect.isNull(map.remove('__proto__'));
+  testEmpty(map);
+}
+
+void testToString() {
+  Expect.equals("{}", jsonify({}).toString());
+  Expect.equals("{a: 0}", jsonify({'a': 0}).toString());
+}
+
+void testConcurrentModifications() {
+  void testIterate(Map map, Iterable iterable, Function f) {
+    Iterator iterator = iterable.iterator;
+    f(map);
+    iterator.moveNext();
+  }
+
+  void testKeys(Map map, Function f) => testIterate(map, map.keys, f);
+  void testValues(Map map, Function f) => testIterate(map, map.values, f);
+
+  void testForEach(Map map, Function f) {
+    map.forEach((key, value) {
+      f(map);
+    });
+  }
+
+  bool throwsCME(Function f) {
+    try {
+      f();
+    } on ConcurrentModificationError catch (e) {
+      return true;
+    } catch (e) {
+      return false;
+    }
+    return false;
+  }
+
+  Map map = {};
+  Expect.isTrue(throwsCME(() => testKeys(jsonify(map),
+      (map) => map['a'] = 0)));
+  Expect.isTrue(throwsCME(() => testValues(jsonify(map),
+      (map) => map['a'] = 0)));
+  Expect.isFalse(throwsCME(() => testForEach(jsonify(map),
+      (map) => map['a'] = 0)));
+
+  Expect.isFalse(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.clear())));
+  Expect.isFalse(throwsCME(() => testValues(jsonify(map),
+      (map) => map.clear())));
+  Expect.isFalse(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.clear())));
+
+  Expect.isFalse(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.remove('a'))));
+  Expect.isFalse(throwsCME(() => testValues(jsonify(map),
+      (map) => map.remove('a'))));
+  Expect.isFalse(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.remove('a'))));
+
+  Expect.isTrue(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.putIfAbsent('a', () => 0))));
+  Expect.isTrue(throwsCME(() => testValues(jsonify(map),
+      (map) => map.putIfAbsent('a', () => 0))));
+  Expect.isFalse(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.putIfAbsent('a', () => 0))));
+
+  Expect.isFalse(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.addAll({}))));
+  Expect.isFalse(throwsCME(() => testValues(jsonify(map),
+      (map) => map.addAll({}))));
+  Expect.isFalse(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.addAll({}))));
+
+  Expect.isTrue(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.addAll({'a': 0}))));
+  Expect.isTrue(throwsCME(() => testValues(jsonify(map),
+      (map) => map.addAll({'a': 0}))));
+  Expect.isFalse(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.addAll({'a': 0}))));
+
+  map = {'a': 1};
+  Expect.isFalse(throwsCME(() => testKeys(jsonify(map),
+      (map) => map['a'] = 0)));
+  Expect.isFalse(throwsCME(() => testValues(jsonify(map),
+      (map) => map['a'] = 0)));
+  Expect.isFalse(throwsCME(() => testForEach(jsonify(map),
+      (map) => map['a'] = 0)));
+
+  Expect.isTrue(throwsCME(() => testKeys(jsonify(map),
+      (map) => map['b'] = 0)));
+  Expect.isTrue(throwsCME(() => testValues(jsonify(map),
+      (map) => map['b'] = 0)));
+  Expect.isTrue(throwsCME(() => testForEach(jsonify(map),
+      (map) => map['b'] = 0)));
+
+  Expect.isTrue(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.clear())));
+  Expect.isTrue(throwsCME(() => testValues(jsonify(map),
+      (map) => map.clear())));
+  Expect.isTrue(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.clear())));
+
+  Expect.isTrue(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.remove('a'))));
+  Expect.isTrue(throwsCME(() => testValues(jsonify(map),
+      (map) => map.remove('a'))));
+  Expect.isTrue(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.remove('a'))));
+
+  Expect.isFalse(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.remove('b'))));
+  Expect.isFalse(throwsCME(() => testValues(jsonify(map),
+      (map) => map.remove('b'))));
+  Expect.isFalse(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.remove('b'))));
+
+  Expect.isFalse(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.putIfAbsent('a', () => 0))));
+  Expect.isFalse(throwsCME(() => testValues(jsonify(map),
+      (map) => map.putIfAbsent('a', () => 0))));
+  Expect.isFalse(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.putIfAbsent('a', () => 0))));
+
+  Expect.isTrue(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.putIfAbsent('b', () => 0))));
+  Expect.isTrue(throwsCME(() => testValues(jsonify(map),
+      (map) => map.putIfAbsent('b', () => 0))));
+  Expect.isTrue(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.putIfAbsent('b', () => 0))));
+
+  Expect.isFalse(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.addAll({}))));
+  Expect.isFalse(throwsCME(() => testValues(jsonify(map),
+      (map) => map.addAll({}))));
+  Expect.isFalse(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.addAll({}))));
+
+  Expect.isFalse(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.addAll({'a': 0}))));
+  Expect.isFalse(throwsCME(() => testValues(jsonify(map),
+      (map) => map.addAll({'a': 0}))));
+  Expect.isFalse(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.addAll({'a': 0}))));
+
+  Expect.isTrue(throwsCME(() => testKeys(jsonify(map),
+      (map) => map.addAll({'b': 0}))));
+  Expect.isTrue(throwsCME(() => testValues(jsonify(map),
+      (map) => map.addAll({'b': 0}))));
+  Expect.isTrue(throwsCME(() => testForEach(jsonify(map),
+      (map) => map.addAll({'b': 0}))));
+}
+
+void testType() {
+  Expect.isTrue(jsonify({}) is Map);
+  Expect.isTrue(jsonify({}) is HashMap);
+  Expect.isTrue(jsonify({}) is LinkedHashMap);
+
+  Expect.isTrue(jsonify({}) is Map<String, dynamic>);
+  Expect.isTrue(jsonify({}) is HashMap<String, dynamic>);
+  Expect.isTrue(jsonify({}) is LinkedHashMap<String, dynamic>);
+
+  Expect.isTrue(jsonify({}) is Map<int, dynamic>);
+  Expect.isTrue(jsonify({}) is HashMap<int, dynamic>);
+  Expect.isTrue(jsonify({}) is LinkedHashMap<int, dynamic>);
+}
+
+void testNonStringKeys() {
+  Map map = jsonify({});
+  map[1] = 2;
+  Expect.equals(1, map.length);
+  Expect.equals(2, map[1]);
+}
+
+void testClear() {
+  Map map = jsonify({'a': 0});
+  map.clear();
+  Expect.equals(0, map.length);
+}
+
+void testListEntry() {
+  Map map = jsonify({'a': [7, 8, {'b': 9}]});
+  List list = map['a'];
+  Expect.equals(3, list.length);
+  Expect.equals(7, list[0]);
+  Expect.equals(8, list[1]);
+  Expect.equals(9, list[2]['b']);
+}