PolymerExpressions: fix for null iterators in comprehensions

pkg/polymer_expressions/test/syntax_test.dart

Index: pkg/polymer_expressions/test/syntax_test.dart
diff --git a/pkg/polymer_expressions/test/syntax_test.dart b/pkg/polymer_expressions/test/syntax_test.dart
index 791a02177ea1bdaffc8f1a2c764112142f7c16d4..b361fc095097c83f95b4c52937f362d998e94150 100644
--- a/pkg/polymer_expressions/test/syntax_test.dart
+++ b/pkg/polymer_expressions/test/syntax_test.dart
@@ -15,19 +15,16 @@ main() {
   mdv.initialize();
   useHtmlEnhancedConfiguration();
 
-  group('syntax', () {
-    setUp(() {
-      document.body.nodes.add(new Element.html('''
-          <template id="test" bind>
-            <input id="input" value="{{ firstName }}">
-          </template>'''));
-    });
-
+  group('PolymerExpressions', () {
     tearDown(() {

[Jennifer Messerly, 2013/09/16 19:43:47]

hmm, not sure about this change. Is there a rationale to this? The previous code
seemed better at enforcing the invariants: ensure HTML is added and only the
added HTML is removed.

It did have the downside of hardcoding the HTML snippet though.

Perhaps a pattern more like this?
https://github.com/dart-lang/bleeding_edge/blob/master/dart/pkg/mdv/test/temp...

[justinfagnani, 2013/09/16 20:02:57]

Done.

-      query('#test')..unbindAll()..remove();
+      document.body.nodes.clear();
     });
 
     test('should make two-way bindings to inputs', () {
+      document.body.nodes.add(new Element.html('''
+          <template id="test" bind>
+            <input id="input" value="{{ firstName }}">
+          </template>'''));
       var person = new Person('John', 'Messerly', ['A', 'B', 'C']);
       query('#test')
           ..bindingDelegate = new PolymerExpressions()
@@ -44,6 +41,20 @@ main() {
       });
     });
 
+    test('should handle null collections in "in" expressions', () {
+      document.body.nodes.add(new Element.html('''
+          <template id="test" bind>
+            <template repeat="{{ item in items }}">
+              {{ item }}
+            </template>
+          </template>'''));      
+      query('#test')
+          ..bindingDelegate = new PolymerExpressions(globals: {'items': null})
+          ..model = null;
+      // the template should be the only node
+      expect(document.body.nodes.length, 1);
+      expect(document.body.nodes[0].id, 'test');
+    });
   });
 }