Use package names as import prefixes when generating code

lib/extension_generator.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.
 
 part of protoc;
 
 class ExtensionGenerator implements ProtobufContainer {
   final String fqname;
   final FieldDescriptorProto _descriptor;
   final ProtobufContainer _parent;
   final GenerationContext _context;
 
   ExtensionGenerator(
       FieldDescriptorProto descriptor,
       ProtobufContainer parent,
       GenerationContext context)
           : this._descriptor = descriptor,
             this._parent = parent,
             this._context = context,
             fqname = parent.fqname == '.' ?
                 '.${descriptor.name}' :
                 '${parent.fqname}.${descriptor.name}';
 
+  String get package => _parent.package;
+
   String get classname {
     String name = new ProtobufField(
         _descriptor, _parent, _context).externalFieldName;
     return _parent is MessageGenerator ? '${_parent.classname}.$name' : name;
   }
 
   void generate(IndentingWriter out) {
     ProtobufField field = new ProtobufField(_descriptor, _parent, _context);
-    String baseType = field.baseType;
+    String baseType = field.baseTypeForPackage(package);
 
     String name = field.externalFieldName;
     String type = field.shortTypeName;
 
-    String typeName = '';
-    ProtobufContainer typeNameContainer = _context[_descriptor.typeName];
-    if (typeNameContainer != null) {
-      typeName = typeNameContainer.classname;
-    }
-
     String extendee = '';
     ProtobufContainer extendeeContainer = _context[_descriptor.extendee];
     if (extendeeContainer != null) {
       extendee = extendeeContainer.classname;
     }
 
 
     String initializer = '';
     String builder = '';
     String valueOf = '';
 
     if (_descriptor.type == FieldDescriptorProto_Type.TYPE_MESSAGE ||
         _descriptor.type == FieldDescriptorProto_Type.TYPE_GROUP) {
       if (_descriptor.label ==
           FieldDescriptorProto_Label.LABEL_REPEATED) {
-        initializer = ',${SP}()${SP}=>${SP}new PbList<${typeName}>()';
-        builder = ',${SP}()${SP}=>${SP}new ${typeName}()';
+        initializer = ',${SP}()${SP}=>${SP}new PbList<${baseType}>()';
+        builder = ',${SP}()${SP}=>${SP}new ${baseType}()';
       } else {
-        initializer = ',${SP}()${SP}=>${SP}new ${typeName}()';
-        builder = ',${SP}()${SP}=>${SP}new ${typeName}()';
+        initializer = ',${SP}()${SP}=>${SP}new ${baseType}()';
+        builder = ',${SP}()${SP}=>${SP}new ${baseType}()';
       }
     } else {
       if (_descriptor.label == FieldDescriptorProto_Label.LABEL_REPEATED) {
         initializer = ',${SP}()${SP}=>${SP}new PbList<${baseType}>()';
       } else if (field.hasInitialization) {
-        initializer = ',${SP}${field.initialization}';
+        var fieldInitialization = field.initializationForPackage(package);
+        initializer = ',${SP}${fieldInitialization}';
       }
     }
 
     if (field.enm) {
       if (initializer.isEmpty) {
         initializer = ',${SP}null';
       }
       if (builder.isEmpty) {
         builder = ',${SP}null';
       }
-      valueOf = ',${SP}(var v)${SP}=>${SP}${field.baseType}.valueOf(v)';
+      var fieldType = field.baseTypeForPackage(package);
+      valueOf = ',${SP}(var v)${SP}=>${SP}${fieldType}.valueOf(v)';
     }
 
     out.println('static final Extension $name${SP}=${SP}'
       'new Extension(\'$extendee\',${SP}\'$name\',${SP}'
       '${_descriptor.number},${SP}GeneratedMessage.$type'
       '${initializer}${builder}${valueOf}'
       ');');
   }
 
   String get name => classname;
 }