Allow application of external mixins to generated dart protos.

lib/file_generator.dart

Index: lib/file_generator.dart
diff --git a/lib/file_generator.dart b/lib/file_generator.dart
index 65cba47953dcc0339f235c9dafccf6333952c871..fd8f0ab93c079fec3f8951628087f41fe603f8c1 100644
--- a/lib/file_generator.dart
+++ b/lib/file_generator.dart
@@ -4,23 +4,33 @@
 
 part of protoc;
 
+final _dartIdentifier = new RegExp(r'^\w+$');
+
 /// Generates the Dart output files for one .proto input file.
 ///
 /// Outputs include .pb.dart, pbenum.dart, and .pbjson.dart.
 class FileGenerator extends ProtobufContainer {
-  /// Returns the the mixin to use by default in this file,
-  /// or null for no mixin by default.
-  static PbMixin _getDefaultMixin(FileDescriptorProto desc) {
-    if (!desc.hasOptions()) return null;
-    if (!desc.options.hasExtension(Dart_options.defaultMixin)) {
-      return null;
-    }
-    var name = desc.options.getExtension(Dart_options.defaultMixin);
-    PbMixin mixin = findMixin(name);
-    if (mixin == null) {
-      throw ("unknown mixin class: ${name}");
-    }
-    return mixin;
+  /// Reads the declared mixins in the file, keyed by name.
+  static Map<String, DartMixin> _getDeclaredMixins(FileDescriptorProto desc) {
+    final mixins = <String, DartMixin>{};
+    if (!desc.hasOptions() || !desc.options.hasExtension(Dart_options.mixins)) {
+      return mixins;
+    }
+    for (DartMixin mixin in desc.options.getExtension(Dart_options.mixins)) {
+      if (mixins.containsKey(mixin.name)) {
+        throw ('Duplicate mixin name: "${mixin.name}"');

[skybrian, 2016/06/22 19:27:18]

style nit: parentheses aren't needed.

[skybrian, 2016/06/22 20:29:52]

When we throw we should give some indication of the location in the file where
the error is. We can't give a line number unfortunately, but we could say
something like:

somefile.proto in 'mixins' file option: duplicate mixin name: SomeMixin

Similarly for other errors.

[frederikmutzel, 2016/06/23 12:30:16]

Done.

[frederikmutzel, 2016/06/23 12:30:16]

Done.

+      }
+      if (!mixin.name.startsWith(_dartIdentifier)) {
+        throw ('Mixin name "${mixin.name}" is not a valid dart class '
+            'identifier');
+      }
+      if (mixin.hasParent() && !mixin.parent.startsWith(_dartIdentifier)) {
+        throw ('Mixin parent "${mixin.parent}" of ${mixin.name} is not a valid '
+            'dart class identifier');
+      }
+      mixins[mixin.name] = mixin;
+    }

[skybrian, 2016/06/22 19:27:18]

Also check for cycles?

[frederikmutzel, 2016/06/23 12:30:16]

Done.

+    return mixins;
   }
 
   final FileDescriptorProto _fileDescriptor;
@@ -45,15 +55,17 @@ class FileGenerator extends ProtobufContainer {
       throw "FAILURE: Import with absolute path is not supported";
     }
 
-    var defaultMixin = _getDefaultMixin(_fileDescriptor);
+    var declaredMixins = _getDeclaredMixins(descriptor);
+    var defaultMixin =

[skybrian, 2016/06/22 20:29:52]

should check that we can find defaultMixin.
It will be checked later, but if we do it here, we can give the proper location
of the error. (It's on the defaultMixin file option, not on the messages.)

[frederikmutzel, 2016/06/23 12:30:16]

Done.

+        descriptor.options?.getExtension(Dart_options.defaultMixin);
 
     // Load and register all enum and message types.
     for (EnumDescriptorProto enumType in _fileDescriptor.enumType) {
       enumGenerators.add(new EnumGenerator(enumType, this));
     }
     for (DescriptorProto messageType in _fileDescriptor.messageType) {
-      messageGenerators
-          .add(new MessageGenerator(messageType, this, defaultMixin));
+      messageGenerators.add(new MessageGenerator(
+          messageType, this, declaredMixins, defaultMixin));
     }
     for (FieldDescriptorProto extension in _fileDescriptor.extension) {
       extensionGenerators.add(new ExtensionGenerator(extension, this));