Allow <template if="{{ expr }}"> to be equivalent to template bind

pkg/mdv/test/template_element_test.dart

 // Copyright (c) 2013, 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 template_element_test;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:html';
 import 'dart:math' as math;
@@ skipping 88 matching lines @@
 
   observeTest('Template bind, no parent', () {
     var div = createTestHtml('<template bind>text</template>');
     var template = div.nodes[0];
     template.remove();
 
     recursivelySetTemplateModel(template, toSymbolMap({}));
     performMicrotaskCheckpoint();
     expect(template.nodes.length, 0);
     expect(template.nextNode, null);
-    // TODO(jmesserly): the JS tests assert that observer callbacks had no
-    // exceptions. How do we replicate this?
   });
 
   observeTest('Template bind, no defaultView', () {
     var div = createTestHtml('<template bind>text</template>');
     var template = div.nodes[0];
     var doc = document.implementation.createHtmlDocument('');
     doc.adoptNode(div);
     recursivelySetTemplateModel(template, toSymbolMap({}));
     performMicrotaskCheckpoint();
     expect(div.nodes.length, 1);
-    // TODO(jmesserly): the JS tests assert that observer callbacks had no
-    // exceptions. How do we replicate this?
   });
 
   observeTest('Template-Empty Bind', () {
     var div = createTestHtml('<template bind>text</template>');
     recursivelySetTemplateModel(div, null);
     performMicrotaskCheckpoint();
     expect(div.nodes.length, 2);
     expect(div.nodes.last.text, 'text');
   });
 
+  observeTest('Template Bind If', () {
+    var div = createTestHtml('<template bind if="{{ foo }}">text</template>');
+    // Note: changed this value from 0->null because zero is not falsey in Dart.
+    // See https://code.google.com/p/dart/issues/detail?id=11956
+    var m = toSymbolMap({ 'foo': null });
+    recursivelySetTemplateModel(div, m);
+    performMicrotaskCheckpoint();
+    expect(div.nodes.length, 1);
+
+    m[sym('foo')] = 1;
+    performMicrotaskCheckpoint();
+    expect(div.nodes.length, 2);
+    expect(div.lastChild.text, 'text');
+  });
+
+  observeTest('Template Bind If, 2', () {
+    var div = createTestHtml(
+        '<template bind="{{ foo }}" if="{{ bar }}">{{ bat }}</template>');
+    var m = toSymbolMap({ 'bar': null, 'foo': { 'bat': 'baz' } });
+    recursivelySetTemplateModel(div, m);
+    performMicrotaskCheckpoint();
+    expect(div.nodes.length, 1);
+
+    m[sym('bar')] = 1;
+    performMicrotaskCheckpoint();
+    expect(div.nodes.length, 2);
+    expect(div.lastChild.text, 'baz');
+  });
+
+  observeTest('Template If', () {
+    var div = createTestHtml('<template if="{{ foo }}">text</template>');
+    // Note: changed this value from 0->null because zero is not falsey in Dart.
+    // See https://code.google.com/p/dart/issues/detail?id=11956
+    var m = toSymbolMap({ 'foo': null });
+    recursivelySetTemplateModel(div, m);
+    performMicrotaskCheckpoint();
+    expect(div.nodes.length, 1);
+
+    m[sym('foo')] = 1;
+    performMicrotaskCheckpoint();
+    expect(div.nodes.length, 2);
+    expect(div.lastChild.text, 'text');
+  });
+
   observeTest('TextTemplateWithNullStringBinding', () {
     var div = createTestHtml('<template bind={{}}>a{{b}}c</template>');
     var model = toSymbolMap({'b': 'B'});
     recursivelySetTemplateModel(div, model);
 
     deliverChanges(model);
     expect(div.nodes.length, 2);
     expect(div.nodes.last.text, 'aBc');
 
     model[sym('b')] = 'b';
@@ skipping 1554 matching lines @@
       k = k is String ? sym(k) : _deepToSymbol(k);
       result[k] = _deepToSymbol(v);
     });
     return result;
   }
   if (value is Iterable) {
     return value.map(_deepToSymbol).toList();
   }
   return value;
 }