Introduce boot.js: this finally makes it possible to load and run Todomvc

lib/src/observable_transform.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.
 
 /**
  * Code transform for @observable. The core transformation is relatively
  * straightforward, and essentially like an editor refactoring. You can find the
  * core implementation in [transformClass], which is ultimately called by
  * [transformObservables], the entry point to this library.
  */
@@ skipping 68 matching lines @@
 
 void transformClass(ClassDeclaration cls, TextEditTransaction code,
     SourceFile file, Messages messages) {
 
   if (hasObservable(cls)) {
     messages.warning('@observable on a class no longer has any effect. '
         'It should be placed on individual fields.',
         _getSpan(file, cls));
   }
 
+  // We'd like to track whether observable was declared explicitly, otherwise
+  // report a warning later below. Because we don't have type analysis (only
+  // syntactic understanding of the code), we only report warnings that are
+  // known to be true.
+  var declaresObservable = false;
+  if (cls.extendsClause != null) {
+    var id = _getSimpleIdentifier(cls.extendsClause.superclass.name);
+    if (id.name == 'ObservableBase') {
+      code.edit(id.offset, id.end, 'ChangeNotifierBase');
+      declaresObservable = true;
+    } else if (id.name == 'ChangeNotifierBase') {
+      declaresObservable = true;
+    } else if (id.name != 'PolymerElement' && id.name != 'CustomElement'
+        && id.name != 'Object') {
+      // TODO(sigmund): this is conservative, consider using type-resolution to
+      // improve this check.
+      declaresObservable = true;
+    }
+  }
+
+  if (cls.withClause != null) {
+    for (var type in cls.withClause.mixinTypes) {
+      var id = _getSimpleIdentifier(type.name);
+      if (id.name == 'ObservableMixin') {
+        code.edit(id.offset, id.end, 'ChangeNotifierMixin');
+        declaresObservable = true;
+        break;
+      } else if (id.name == 'ChangeNotifierMixin') {
+        declaresObservable = true;
+        break;
+      } else {
+        // TODO(sigmund): this is conservative, consider using type-resolution
+        // to improve this check.
+        declaresObservable = true;
+      }
+    }
+  }
+
+  if (!declaresObservable && cls.implementsClause != null) {
+    // TODO(sigmund): consider adding type-resolution to give a more precise
+    // answer.
+    declaresObservable = true;
+  }
+
   // Track fields that were transformed.
   var instanceFields = new Set<String>();
   var getters = new List<String>();
   var setters = new List<String>();
 
   for (var member in cls.members) {
     if (member is FieldDeclaration) {
       bool isStatic = hasKeyword(member.keyword, Keyword.STATIC);
       if (isStatic) {
         if (hasObservable(member)){
           messages.warning('Static fields can no longer be observable. '
               'Observable fields should be put in an observable objects.',
               _getSpan(file, member));
         }
         continue;
       }
       if (hasObservable(member)) {
+        if (!declaresObservable) {
+          messages.warning('Observable fields should be put in an observable'
+              ' objects. Please declare that this class extends from '
+              'ObservableBase, includes ObservableMixin, or implements '
+              'Observable.',
+              _getSpan(file, member));
+
+        }
         transformFields(member.fields, code, member.offset, member.end);
 
         var names = member.fields.variables.map((v) => v.name.name);
 
         getters.addAll(names);
         if (!_isReadOnly(member.fields)) {
           setters.addAll(names);
           instanceFields.addAll(names);
         }
       }
@@ skipping 17 matching lines @@
   }
 
   // Fix initializers, because they aren't allowed to call the setter.
   for (var member in cls.members) {
     if (member is ConstructorDeclaration) {
       fixConstructor(member, code, instanceFields);
     }
   }
 }
 
+SimpleIdentifier _getSimpleIdentifier(Identifier id) =>
+    id is PrefixedIdentifier ? id.identifier : id;
+
 
 /**
  * Generates `getValueWorkaround` and `setValueWorkaround`. These will go away
  * shortly once dart2js supports mirrors. For the moment they provide something
  * that the binding system can use.
  */
 void mirrorWorkaround(ClassDeclaration cls, TextEditTransaction code,
     List<String> getters, List<String> setters) {
 
   var sb = new StringBuffer('\ngetValueWorkaround(key) {\n');
@@ skipping 108 matching lines @@
 $type __\$$name$initializer;
 $type get $name => __\$$name;
 set $name($type value) {
   __\$$name = notifyPropertyChange(const Symbol('$name'), __\$$name, value);
 }
 '''.replaceAll('\n', '\n$indent'));
   }
 
   code.edit(begin, end, '$replace');
 }