Allow application of external mixins to generated dart protos.

lib/protobuf_field.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 ProtobufField {
   static final RegExp HEX_LITERAL_REGEX =
       new RegExp(r'^0x[0-9a-f]+$', multiLine: false, caseSensitive: false);
   static final RegExp INTEGER_LITERAL_REGEX = new RegExp(r'^[+-]?[0-9]+$');
@@ skipping 37 matching lines @@
   bool get isRequired =>
       descriptor.label == FieldDescriptorProto_Label.LABEL_REQUIRED;
 
   bool get isRepeated =>
       descriptor.label == FieldDescriptorProto_Label.LABEL_REPEATED;
 
   /// True if the field is to be encoded with [packed=true] encoding.
   bool get isPacked =>
       isRepeated && descriptor.options != null && descriptor.options.packed;
 
+  /// Whether the field has the `overrideGetter` annotation set to true.
+  bool get overridesGetter => _hasBooleanOption(Dart_options.overrideGetter);
+
+  /// Whether the field has the `overrideSetter` annotation set to true.
+  bool get overridesSetter => _hasBooleanOption(Dart_options.overrideSetter);
+
+  /// Whether the field has the `overrideHasMethod` annotation set to true.
+  bool get overridesHasMethod =>
+      _hasBooleanOption(Dart_options.overrideHasMethod);
+
+  /// Whether the field has the `overrideClearMethod` annotation set to true.
+  bool get overridesClearMethod =>
+      _hasBooleanOption(Dart_options.overrideClearMethod);
+
   /// True if this field uses the Int64 from the fixnum package.
   bool get needsFixnumImport => baseType.unprefixed == "Int64";
 
   /// Returns the expression to use for the Dart type.
   ///
   /// This will be a List for repeated types.
   /// [package] is the package where we are generating code.
   String getDartType(String package) {
     if (isRepeated) return baseType.getRepeatedDartType(package);
     return baseType.getDartType(package);
@@ skipping 168 matching lines @@
     return '\'$value\'';
   }
 
   String _getDefaultAsInt32Expr(String noDefault) {
     if (descriptor.hasDefaultValue() && '0' != descriptor.defaultValue) {
       return '${descriptor.defaultValue}';
     }
     return noDefault;
   }
 
+  bool _hasBooleanOption(Extension extension) =>
+      descriptor?.options?.getExtension(extension) ?? false;
+
   get _invalidDefaultValue => "dart-protoc-plugin:"
       " invalid default value (${descriptor.defaultValue})"
       " found in field $fqname";
 
   _typeNotImplemented(String methodName) => "dart-protoc-plugin:"
       " $methodName not implemented for type (${descriptor.type})"
       " found in field $fqname";
 }