protoc_plugin/oo.patch

diff --git a/lib/message_generator.dart b/../../dart-protoc-plugin/lib/message_generator.dart
index 5c9c072..65ca39c 100644
--- a/lib/message_generator.dart
+++ b/../../dart-protoc-plugin/lib/message_generator.dart
@@ -4,6 +4,19 @@
 
 part of protoc;
 
+class OneofEnumGenerator {
+  static void generate(
+      IndentingWriter out, String classname, List<ProtobufField> fields) {
+    out.addBlock('enum ${classname} {', '}\n', () {
+      for (ProtobufField field in fields) {
+        final name = field.memberNames.fieldName;
+        out.println('$name, ');
+      }
+      out.println('unset');
+    });
+  }
+}
+
 class MessageGenerator extends ProtobufContainer {
   /// Returns the mixin for this message, or null if none.
   ///
@@ -56,37 +69,46 @@ class MessageGenerator extends ProtobufContainer {
   final List<EnumGenerator> _enumGenerators = <EnumGenerator>[];
   final List<MessageGenerator> _messageGenerators = <MessageGenerator>[];
   final List<ExtensionGenerator> _extensionGenerators = <ExtensionGenerator>[];
+  // Stores the list of fields belonging to each oneof declaration identified
+  // by the index in the containing types's oneof_decl list.
+  final List<List<ProtobufField>> _oneofFields;
+  List<OneofNames> _oneofNames;
 
   // populated by resolve()
   List<ProtobufField> _fieldList;
 
+  Set<String> _usedTopLevelNames;
+
   MessageGenerator(
       DescriptorProto descriptor,
       ProtobufContainer parent,
       Map<String, PbMixin> declaredMixins,
       PbMixin defaultMixin,
-      Set<String> usedNames)
+      this._usedTopLevelNames)
       : _descriptor = descriptor,
         _parent = parent,
-        classname = messageOrEnumClassName(descriptor.name, usedNames,
+        classname = messageOrEnumClassName(descriptor.name, _usedTopLevelNames,
             parent: parent?.classname ?? ''),
         assert(parent != null),
         fullName = parent.fullName == ''
             ? descriptor.name
             : '${parent.fullName}.${descriptor.name}',
         mixin = _getMixin(descriptor, parent.fileGen.descriptor, declaredMixins,
-            defaultMixin) {
+            defaultMixin),
+        _oneofFields =
+            List.generate(descriptor.oneofDecl.length, (int index) => []) {
     for (EnumDescriptorProto e in _descriptor.enumType) {
-      _enumGenerators.add(new EnumGenerator(e, this, usedNames));
+      _enumGenerators.add(new EnumGenerator(e, this, _usedTopLevelNames));
     }
 
     for (DescriptorProto n in _descriptor.nestedType) {
       _messageGenerators.add(new MessageGenerator(
-          n, this, declaredMixins, defaultMixin, usedNames));
+          n, this, declaredMixins, defaultMixin, _usedTopLevelNames));
     }
 
     for (FieldDescriptorProto x in _descriptor.extension) {
-      _extensionGenerators.add(new ExtensionGenerator(x, this, usedNames));
+      _extensionGenerators
+          .add(new ExtensionGenerator(x, this, _usedTopLevelNames));
     }
   }
 
@@ -138,12 +160,19 @@ class MessageGenerator extends ProtobufContainer {
     if (_fieldList != null) throw new StateError("message already resolved");
 
     var reserved = mixin?.findReservedNames() ?? const <String>[];
-    var fields = messageFieldNames(_descriptor, reserved: reserved);
+    MemberNames members = messageMemberNames(
+        _descriptor, classname, _usedTopLevelNames,
+        reserved: reserved);
 
     _fieldList = <ProtobufField>[];
-    for (MemberNames names in fields.values) {
-      _fieldList.add(new ProtobufField.message(names, this, ctx));
+    for (FieldNames names in members.fieldNames) {
+      ProtobufField field = new ProtobufField.message(names, this, ctx);
+      if (field.descriptor.hasOneofIndex()) {
+        _oneofFields[field.descriptor.oneofIndex].add(field);
+      }
+      _fieldList.add(field);
     }
+    _oneofNames = members.oneofNames;
 
     for (var m in _messageGenerators) {
       m.resolve(ctx);
@@ -223,6 +252,11 @@ class MessageGenerator extends ProtobufContainer {
       m.generate(out);
     }
 
+    for (OneofNames oneof in _oneofNames) {
+      OneofEnumGenerator.generate(
+          out, oneof.oneofEnumName, _oneofFields[oneof.index]);
+    }
+
     var mixinClause = '';
     if (mixin != null) {
       var mixinNames = mixin.findMixinsToApply().map((m) => m.name);
@@ -235,6 +269,17 @@ class MessageGenerator extends ProtobufContainer {
     out.addBlock(
         'class ${classname} extends $_protobufImportPrefix.GeneratedMessage${mixinClause} {',
         '}', () {
+      for (OneofNames oneof in _oneofNames) {
+        out.addBlock(
+            'static const Map<int, ${oneof.oneofEnumName}> ${oneof.byTagMapName} = {',
+            '};', () {
+          for (ProtobufField field in _oneofFields[oneof.index]) {
+            out.println(
+                '${field.number} : ${oneof.oneofEnumName}.${field.memberNames.fieldName},');
+          }
+          out.println('0 : ${oneof.oneofEnumName}.unset');
+        });
+      }
       out.addBlock(
           'static final $_protobufImportPrefix.BuilderInfo _i = '
           'new $_protobufImportPrefix.BuilderInfo(\'${messageName}\'$packageClause)',
@@ -244,6 +289,12 @@ class MessageGenerator extends ProtobufContainer {
           out.println(field.generateBuilderInfoCall(fileGen, dartFieldName));
         }
 
+        for (int oneof = 0; oneof < _oneofFields.length; oneof++) {
+          List<int> tags =
+              _oneofFields[oneof].map((ProtobufField f) => f.number).toList();
+          out.println("..oo($oneof, ${tags})");
+        }
+
         if (_descriptor.extensionRange.length > 0) {
           out.println('..hasExtensions = true');
         }
@@ -375,12 +426,23 @@ class MessageGenerator extends ProtobufContainer {
   }
 
   void generateFieldsAccessorsMutators(IndentingWriter out) {
+    _oneofNames
+        .forEach((OneofNames oneof) => generateoneOfAccessors(out, oneof));
+
     for (ProtobufField field in _fieldList) {
       out.println();
       generateFieldAccessorsMutators(field, out);
     }
   }
 
+  void generateoneOfAccessors(IndentingWriter out, OneofNames oneof) {
+    out.println();
+    out.println("${oneof.oneofEnumName} ${oneof.whichOneofMethodName}() "
+        "=> ${oneof.byTagMapName}[\$_whichOneof(${oneof.index})];");
+    out.println('void ${oneof.clearMethodName}() '
+        '=> clearField(\$_whichOneof(${oneof.index}));');
+  }
+
   void generateFieldAccessorsMutators(
       ProtobufField field, IndentingWriter out) {
     var fieldTypeString = field.getDartType(fileGen);
diff --git a/lib/names.dart b/../../dart-protoc-plugin/lib/names.dart
index a974bec..251f9f0 100644
--- a/lib/names.dart
+++ b/../../dart-protoc-plugin/lib/names.dart
@@ -10,8 +10,14 @@ import 'package:protoc_plugin/src/descriptor.pb.dart';
 /// to check its type and range.
 const checkItem = '\$checkItem';
 
-/// The Dart member names in a GeneratedMessage subclass for one protobuf field.
 class MemberNames {
+  List<FieldNames> fieldNames;
+  List<OneofNames> oneofNames;
+  MemberNames(this.fieldNames, this.oneofNames);
+}
+
+/// The Dart member names in a GeneratedMessage subclass for one protobuf field.
+class FieldNames {
   /// The descriptor of the field these member names apply to.
   final FieldDescriptorProto descriptor;
 
@@ -32,10 +38,33 @@ class MemberNames {
   /// `null` for repeated fields.
   final String clearMethodName;
 
-  MemberNames(this.descriptor, this.index, this.fieldName,
+  FieldNames(this.descriptor, this.index, this.fieldName,
       {this.hasMethodName, this.clearMethodName});
 }
 
+// The Dart names associated with a oneof declaration.
+class OneofNames {
+  final OneofDescriptorProto descriptor;
+
+  // Index in the containing type's oneof_decl list.
+  final int index;
+
+  // Identifier for the generated whichX() method, without braces.
+  final String whichOneofMethodName;
+
+  // Identifier for the generated clearX() method, without braces.
+  final String clearMethodName;
+
+  // Identifier for the generated enum definition.
+  final String oneofEnumName;
+
+  //  Identifier for the _XByTag map.
+  final String byTagMapName;
+
+  OneofNames(this.descriptor, this.index, this.clearMethodName,
+      this.whichOneofMethodName, this.oneofEnumName, this.byTagMapName);
+}
+
 /// Move any initial underscores in [input] to the end.
 ///
 /// According to the spec identifiers cannot start with _, but it seems to be
@@ -143,6 +172,13 @@ Iterable<String> defaultSuffixes() sync* {
   }
 }
 
+String oneofEnumClassName(
+    String descriptorName, Set<String> usedNames, String parent) {
+  descriptorName = '${parent}_${underscoresToCamelCase(descriptorName)}';
+  return disambiguateName(
+      avoidInitialUnderscore(descriptorName), usedNames, defaultSuffixes());
+}
+
 /// Chooses the name of the Dart class to generate for a proto message or enum.
 ///
 /// For a nested message or enum, [parent] should be provided
@@ -170,17 +206,18 @@ Iterable<String> enumSuffixes() sync* {
   }
 }
 
-/// Chooses the GeneratedMessage member names for each field.
+/// Chooses the GeneratedMessage member names for each field and names
+/// associated with each oneof declaration.
 ///
 /// Additional names to avoid can be supplied using [reserved].
 /// (This should only be used for mixins.)
 ///
-/// Returns a map from the field name in the .proto file to its
-/// corresponding MemberNames.
+/// Returns [MemberNames] which holds a list with [FieldNames] and a list with [OneofNames].
 ///
 /// Throws [DartNameOptionException] if a field has this option and
 /// it's set to an invalid name.
-Map<String, MemberNames> messageFieldNames(DescriptorProto descriptor,
+MemberNames messageMemberNames(DescriptorProto descriptor,
+    String parentClassName, Set<String> usedTopLevelNames,
     {Iterable<String> reserved = const []}) {
   var sorted = new List<FieldDescriptorProto>.from(descriptor.field)
     ..sort((FieldDescriptorProto a, FieldDescriptorProto b) {
@@ -200,10 +237,10 @@ Map<String, MemberNames> messageFieldNames(DescriptorProto descriptor,
     ..addAll(reservedMemberNames)
     ..addAll(reserved);
 
-  var memberNames = <String, MemberNames>{};
+  List<FieldNames> fieldNames = <FieldNames>[];
 
-  void takeNames(MemberNames chosen) {
-    memberNames[chosen.descriptor.name] = chosen;
+  void takeFieldNames(FieldNames chosen) {
+    fieldNames.add(chosen);
 
     existingNames.add(chosen.fieldName);
     if (chosen.hasMethodName != null) {
@@ -219,7 +256,7 @@ Map<String, MemberNames> messageFieldNames(DescriptorProto descriptor,
   // Explicitly setting a name that's already taken is a build error.
   for (var field in sorted) {
     if (_nameOption(field).isNotEmpty) {
-      takeNames(_memberNamesFromOption(
+      takeFieldNames(_memberNamesFromOption(
           descriptor, field, indexes[field.name], existingNames));
     }
   }
@@ -229,23 +266,55 @@ Map<String, MemberNames> messageFieldNames(DescriptorProto descriptor,
   for (var field in sorted) {
     if (_nameOption(field).isEmpty) {
       var index = indexes[field.name];
-      takeNames(_unusedMemberNames(field, index, existingNames));
+      takeFieldNames(_unusedMemberNames(field, index, existingNames));
     }
   }
 
-  // Return a map with entries in sorted order.
-  var result = <String, MemberNames>{};
-  for (var field in sorted) {
-    result[field.name] = memberNames[field.name];
+  List<OneofNames> oneofNames = <OneofNames>[];
+
+  void takeOneofNames(OneofNames chosen) {
+    oneofNames.add(chosen);
+
+    if (chosen.whichOneofMethodName != null) {
+      existingNames.add(chosen.whichOneofMethodName);
+    }
+    if (chosen.clearMethodName != null) {
+      existingNames.add(chosen.clearMethodName);
+    }
+    if (chosen.byTagMapName != null) {
+      existingNames.add(chosen.byTagMapName);
+    }
+  }
+
+  List<String> oneofNameVariants(String name) {
+    return [_defaultWhichMethodName(name), _defaultClearMethodName(name)];
   }
-  return result;
+
+  for (int i = 0; i < descriptor.oneofDecl.length; i++) {
+    OneofDescriptorProto oneof = descriptor.oneofDecl[i];
+
+    String oneofName = disambiguateName(
+        underscoresToCamelCase(oneof.name), existingNames, defaultSuffixes(),
+        generateVariants: oneofNameVariants);
+
+    String oneofEnumName =
+        oneofEnumClassName(oneof.name, usedTopLevelNames, parentClassName);
+
+    String enumMapName = disambiguateName(
+        '_${oneofEnumName}ByTag', existingNames, defaultSuffixes());
+
+    takeOneofNames(OneofNames(oneof, i, _defaultClearMethodName(oneofName),
+        _defaultWhichMethodName(oneofName), oneofEnumName, enumMapName));
+  }
+
+  return MemberNames(fieldNames, oneofNames);
 }
 
 /// Chooses the member names for a field that has the 'dart_name' option.
 ///
 /// If the explicitly-set Dart name is already taken, throw an exception.
 /// (Fails the build.)
-MemberNames _memberNamesFromOption(DescriptorProto message,
+FieldNames _memberNamesFromOption(DescriptorProto message,
     FieldDescriptorProto field, int index, Set<String> existingNames) {
   // TODO(skybrian): provide more context in errors (filename).
   var where = "${message.name}.${field.name}";
@@ -268,7 +337,7 @@ MemberNames _memberNamesFromOption(DescriptorProto message,
   checkAvailable(name);
 
   if (_isRepeated(field)) {
-    return new MemberNames(field, index, name);
+    return new FieldNames(field, index, name);
   }
 
   String hasMethod = "has${_capitalize(name)}";
@@ -277,7 +346,7 @@ MemberNames _memberNamesFromOption(DescriptorProto message,
   String clearMethod = "clear${_capitalize(name)}";
   checkAvailable(clearMethod);
 
-  return new MemberNames(field, index, name,
+  return new FieldNames(field, index, name,
       hasMethodName: hasMethod, clearMethodName: clearMethod);
 }
 
@@ -289,10 +358,10 @@ Iterable<String> _memberNamesSuffix(int number) sync* {
   }
 }
 
-MemberNames _unusedMemberNames(
+FieldNames _unusedMemberNames(
     FieldDescriptorProto field, int index, Set<String> existingNames) {
   if (_isRepeated(field)) {
-    return new MemberNames(
+    return new FieldNames(
         field,
         index,
         disambiguateName(_defaultFieldName(_fieldMethodSuffix(field)),
@@ -310,7 +379,7 @@ MemberNames _unusedMemberNames(
   String name = disambiguateName(_fieldMethodSuffix(field), existingNames,
       _memberNamesSuffix(field.number),
       generateVariants: generateNameVariants);
-  return new MemberNames(field, index, _defaultFieldName(name),
+  return new FieldNames(field, index, _defaultFieldName(name),
       hasMethodName: _defaultHasMethodName(name),
       clearMethodName: _defaultClearMethodName(name));
 }
@@ -327,6 +396,9 @@ String _defaultHasMethodName(String fieldMethodSuffix) =>
 String _defaultClearMethodName(String fieldMethodSuffix) =>
     'clear$fieldMethodSuffix';
 
+String _defaultWhichMethodName(String oneofMethodSuffix) =>
+    'which$oneofMethodSuffix';
+
 /// The suffix to use for this field in Dart method names.
 /// (It should be camelcase and begin with an uppercase letter.)
 String _fieldMethodSuffix(FieldDescriptorProto field) {
@@ -334,7 +406,7 @@ String _fieldMethodSuffix(FieldDescriptorProto field) {
   if (name.isNotEmpty) return _capitalize(name);
 
   if (field.type != FieldDescriptorProto_Type.TYPE_GROUP) {
-    return _underscoresToCamelCase(field.name);
+    return underscoresToCamelCase(field.name);
   }
 
   // For groups, use capitalization of 'typeName' rather than 'name'.
@@ -343,10 +415,10 @@ String _fieldMethodSuffix(FieldDescriptorProto field) {
   if (index != -1) {
     name = name.substring(index + 1);
   }
-  return _underscoresToCamelCase(name);
+  return underscoresToCamelCase(name);
 }
 
-String _underscoresToCamelCase(s) => s.split('_').map(_capitalize).join('');
+String underscoresToCamelCase(s) => s.split('_').map(_capitalize).join('');
 
 String _capitalize(s) =>
     s.isEmpty ? s : '${s[0].toUpperCase()}${s.substring(1)}';
diff --git a/lib/protobuf_field.dart b/../../dart-protoc-plugin/lib/protobuf_field.dart
index 83eca16..3482161 100644
--- a/lib/protobuf_field.dart
+++ b/../../dart-protoc-plugin/lib/protobuf_field.dart
@@ -20,20 +20,20 @@ class ProtobufField {
   final FieldDescriptorProto descriptor;
 
   /// Dart names within a GeneratedMessage or `null` for an extension.
-  final MemberNames memberNames;
+  final FieldNames memberNames;
 
   final String fullName;
   final BaseType baseType;
 
   ProtobufField.message(
-      MemberNames names, ProtobufContainer parent, GenerationContext ctx)
+      FieldNames names, ProtobufContainer parent, GenerationContext ctx)
       : this._(names.descriptor, names, parent, ctx);
 
   ProtobufField.extension(FieldDescriptorProto descriptor,
       ProtobufContainer parent, GenerationContext ctx)
       : this._(descriptor, null, parent, ctx);
 
-  ProtobufField._(FieldDescriptorProto descriptor, MemberNames dartNames,
+  ProtobufField._(FieldDescriptorProto descriptor, FieldNames dartNames,
       ProtobufContainer parent, GenerationContext ctx)
       : this.descriptor = descriptor,
         this.memberNames = dartNames,