Use package names as import prefixes when generating code

lib/extension_generator.dart

Index: lib/extension_generator.dart
diff --git a/lib/extension_generator.dart b/lib/extension_generator.dart
index e78cd1f39daf0033482310f17cd81dc61cd968d8..c7b5266d2d4a916e3bdc4d0ef207d4f3f0f69152 100644
--- a/lib/extension_generator.dart
+++ b/lib/extension_generator.dart
@@ -21,6 +21,8 @@ class ExtensionGenerator implements ProtobufContainer {
                 '.${descriptor.name}' :
                 '${parent.fqname}.${descriptor.name}';
 
+  String get package => _parent.package;
+
   String get classname {
     String name = new ProtobufField(
         _descriptor, _parent, _context).externalFieldName;
@@ -29,17 +31,11 @@ class ExtensionGenerator implements ProtobufContainer {
 
   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) {
@@ -55,17 +51,18 @@ class ExtensionGenerator implements ProtobufContainer {
         _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}';
       }
     }
 
@@ -76,7 +73,8 @@ class ExtensionGenerator implements ProtobufContainer {
       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}'