Changes in polymer-expressions to prepare for codegen in polymer:

pkg/polymer_expressions/lib/polymer_expressions.dart

Index: pkg/polymer_expressions/lib/polymer_expressions.dart
diff --git a/pkg/polymer_expressions/lib/polymer_expressions.dart b/pkg/polymer_expressions/lib/polymer_expressions.dart
index 36ea3524adbc8d7acfc4d1e2e8598353872a4eb7..ae88ace5fc96838db45c4aad24e9b9fc1cab7580 100644
--- a/pkg/polymer_expressions/lib/polymer_expressions.dart
+++ b/pkg/polymer_expressions/lib/polymer_expressions.dart
@@ -30,7 +30,6 @@ library polymer_expressions;
 import 'dart:async';
 import 'dart:html';
 
-import 'package:logging/logging.dart';
 import 'package:observe/observe.dart';
 import 'package:template_binding/template_binding.dart';
 
@@ -39,8 +38,6 @@ import 'expression.dart';
 import 'parser.dart';
 import 'src/globals.dart';
 
-final Logger _logger = new Logger('polymer_expressions');
-
 // TODO(justin): Investigate XSS protection
 Object _classAttributeConverter(v) =>
     (v is Map) ? v.keys.where((k) => v[k] == true).join(' ') :
@@ -64,8 +61,7 @@ class PolymerExpressions extends BindingDelegate {
    * [DEFAULT_GLOBALS] will be used.
    */
   PolymerExpressions({Map<String, Object> globals})
-      : globals = (globals == null) ?
-          new Map<String, Object>.from(DEFAULT_GLOBALS) : globals;
+      : globals = globals == null ? DEFAULT_GLOBALS : globals;

[Siggi Cherem (dart-lang), 2014/03/21 01:43:46]

I don't copy it here anymore because we now use the map as read-only. Scopes
create their copy internally.

[Jennifer Messerly, 2014/03/21 20:08:54]

Hmmm, the idea here was that users can dynamically add to globals (probably just
at startup) to the Polymer syntax, similar to JS. If we take that away we should
at least fix the spots in Polymer where the user has no control. Actually our
_PolymerExpressionsWithEventDelegate looks like it became totally private again
:| ... not sure how folks are supposed to be able to customize it in Dart.

[Siggi Cherem (dart-lang), 2014/03/21 21:09:47]

Done. Made _PolymerExpressionsWithEventDelegate public as well. I think people
were doing customization by recreating that class (coping the body of
prepareBinding) :-/

 
   prepareBinding(String path, name, node) {
     if (path == null) return null;
@@ -118,10 +114,11 @@ class _Binding extends Bindable {
   static _oneTime(Expression expr, Scope scope, [converter]) {
     try {
       return _convertValue(eval(expr, scope), scope, converter);
-    } on EvalException catch (e) {
-      _logger.warning("Error evaluating expression '$expr': ${e.message}");
-      return null;
+    } catch (e, s) {
+      new Completer().completeError(

[Jennifer Messerly, 2014/03/21 20:08:54]

nice!

+          "Error evaluating expression '$expr': $e", s);
     }
+    return null;
   }
 
   _setValue(v) {
@@ -133,12 +130,8 @@ class _Binding extends Bindable {
     if (v is Comprehension) {
       // convert the Comprehension into a list of scopes with the loop
       // variable added to the scope
-      return v.iterable.map((i) {
-        var vars = new Map();
-        vars[v.identifier] = i;
-        Scope childScope = new Scope(parent: scope, variables: vars);
-        return childScope;
-      }).toList(growable: false);
+      return v.iterable.map((i) => scope.childScope(v.identifier, i))
+          .toList(growable: false);
     } else {
       return converter == null ? v : converter(v);
     }
@@ -152,8 +145,9 @@ class _Binding extends Bindable {
   set value(v) {
     try {
       assign(_expr, v, _scope);
-    } on EvalException catch (e) {
-      _logger.warning("Error evaluating expression '$_expr': ${e.message}");
+    } catch (e, s) {
+      new Completer().completeError(
+          "Error evaluating expression '$_expr': $e", s);
     }
   }
 
@@ -163,14 +157,16 @@ class _Binding extends Bindable {
     _callback = callback;
     final expr = observe(_expr, _scope);
     _expr = expr;
-    _sub = expr.onUpdate.listen(_setValue)..onError((e) {
-      _logger.warning("Error evaluating expression '$_expr': ${e.message}");
+    _sub = expr.onUpdate.listen(_setValue)..onError((e, s) {
+      new Completer().completeError(
+          "Error evaluating expression '$expr': $e", s);
     });
     try {
       update(expr, _scope);
       _value = _convertValue(expr.currentValue, _scope, _converter);
-    } on EvalException catch (e) {
-      _logger.warning("Error evaluating expression '$_expr': ${e.message}");
+    } catch (e, s) {
+      new Completer().completeError(
+          "Error evaluating expression '$expr': $e", s);
     }
     return _value;
   }