protoc_plugin/lib/message_generator.dart - protobuf - Git at Google

 // 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;

 /// Generates the Dart enum corresponding to a oneof declaration.
 ///
 /// The enum is used to represent the state of a oneof when using the
 /// corresponding which-method.
 class OneofEnumGenerator {
   static void generate(
       IndentingWriter out, String classname, List<ProtobufField> fields) {
     out.addBlock('enum ${classname} {', '}\n', () {
       for (ProtobufField field in fields) {
         final name = oneofEnumMemberName(field.memberNames.fieldName);
         out.println('$name, ');
       }
       out.println('notSet');
     });
   }
 }

 class MessageGenerator extends ProtobufContainer {
   /// The name of the Dart class to generate.
   final String classname;

   /// The fully-qualified name of the message (without any leading '.').
   final String fullName;

   /// The part of the fully qualified name that comes after the package prefix.
   ///
   /// For nested messages this will include the names of the parents.
   ///
   /// For example:
   /// ```
   /// package foo;
   ///
   /// message Container {
   ///   message Nested {
   ///     int32 int32_value = 1;
   ///   }
   /// }
   /// ```
   /// The nested message will have a `fullName` of 'foo.Container.Nested', and a
   /// `messageName` of 'Container.Nested'.
   String get messageName =>
       fullName.substring(package.isEmpty ? 0 : package.length + 1);

   PbMixin mixin;

   final ProtobufContainer _parent;
   final DescriptorProto _descriptor;
   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;

   List<int> _fieldPath;
   final List<int> _fieldPathSegment;

   /// See [[ProtobufContainer]
   List<int> get fieldPath =>
       _fieldPath ??= List.from(_parent.fieldPath)..addAll(_fieldPathSegment);

   // populated by resolve()
   List<ProtobufField> _fieldList;

   Set<String> _usedTopLevelNames;

   MessageGenerator._(
       DescriptorProto descriptor,
       ProtobufContainer parent,
       Map<String, PbMixin> declaredMixins,
       PbMixin defaultMixin,
       this._usedTopLevelNames,
       int repeatedFieldIndex,
       int fieldIdTag)
       : _descriptor = descriptor,
         _parent = parent,
         _fieldPathSegment = [fieldIdTag, repeatedFieldIndex],
         classname = messageOrEnumClassName(descriptor.name, _usedTopLevelNames,
             parent: parent?.classname ?? ''),
         assert(parent != null),
         fullName = parent.fullName == ''
             ? descriptor.name
             : '${parent.fullName}.${descriptor.name}',
         _oneofFields =
             List.generate(descriptor.oneofDecl.length, (int index) => []) {
     mixin = _getMixin(declaredMixins, defaultMixin);
     for (var i = 0; i < _descriptor.enumType.length; i++) {
       EnumDescriptorProto e = _descriptor.enumType[i];
       _enumGenerators.add(EnumGenerator.nested(e, this, _usedTopLevelNames, i));
     }

     for (var i = 0; i < _descriptor.nestedType.length; i++) {
       DescriptorProto n = _descriptor.nestedType[i];
       _messageGenerators.add(MessageGenerator.nested(
           n, this, declaredMixins, defaultMixin, _usedTopLevelNames, i));
     }

     // Extensions within messages won't create top-level classes and don't need
     // to check against / be added to top-level reserved names.
     final usedExtensionNames = Set<String>()..addAll(forbiddenExtensionNames);
     for (var i = 0; i < _descriptor.extension.length; i++) {
       FieldDescriptorProto x = _descriptor.extension[i];
       _extensionGenerators
           .add(ExtensionGenerator.nested(x, this, usedExtensionNames, i));
     }
   }

   static const _topLevelMessageTag = 4;
   static const _nestedMessageTag = 3;
   static const _messageFieldTag = 2;

   MessageGenerator.topLevel(
       DescriptorProto descriptor,
       ProtobufContainer parent,
       Map<String, PbMixin> declaredMixins,
       PbMixin defaultMixin,
       Set<String> usedNames,
       int repeatedFieldIndex)
       : this._(descriptor, parent, declaredMixins, defaultMixin, usedNames,
             repeatedFieldIndex, _topLevelMessageTag);

   MessageGenerator.nested(
       DescriptorProto descriptor,
       ProtobufContainer parent,
       Map<String, PbMixin> declaredMixins,
       PbMixin defaultMixin,
       Set<String> usedNames,
       int repeatedFieldIndex)
       : this._(descriptor, parent, declaredMixins, defaultMixin, usedNames,
             repeatedFieldIndex, _nestedMessageTag);

   String get package => _parent.package;

   /// The generator of the .pb.dart file that will declare this type.
   FileGenerator get fileGen => _parent.fileGen;

   /// Throws an exception if [resolve] hasn't been called yet.
   void checkResolved() {
     if (_fieldList == null) {
       throw StateError("message not resolved: ${fullName}");
     }
   }

   /// Returns a const expression that evaluates to the JSON for this message.
   /// [usage] represents the .pb.dart file where the expression will be used.
   String getJsonConstant(FileGenerator usage) {
     var name = "$classname\$json";
     if (usage.protoFileUri == fileGen.protoFileUri) {
       return name;
     }
     return "$fileImportPrefix.$name";
   }

   /// Adds all mixins used in this message and any submessages.
   void addMixinsTo(Set<PbMixin> output) {
     if (mixin != null) {
       output.addAll(mixin.findMixinsToApply());
     }
     for (var m in _messageGenerators) {
       m.addMixinsTo(output);
     }
   }

   // Registers message and enum types that can be used elsewhere.
   void register(GenerationContext ctx) {
     ctx.registerFieldType(this);
     for (var m in _messageGenerators) {
       m.register(ctx);
     }
     for (var e in _enumGenerators) {
       e.register(ctx);
     }
   }

   // Creates fields and resolves extension targets.
   void resolve(GenerationContext ctx) {
     if (_fieldList != null) throw StateError("message already resolved");

     var reserved = mixin?.findReservedNames() ?? const <String>[];
     MemberNames members = messageMemberNames(
         _descriptor, classname, _usedTopLevelNames,
         reserved: reserved);

     _fieldList = <ProtobufField>[];
     for (FieldNames names in members.fieldNames) {
       ProtobufField field = 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);
     }
     for (var x in _extensionGenerators) {
       x.resolve(ctx);
     }
   }

   bool get needsFixnumImport {
     if (_fieldList == null) throw StateError("message not resolved");
     for (var field in _fieldList) {
       if (field.needsFixnumImport) return true;
     }
     for (var m in _messageGenerators) {
       if (m.needsFixnumImport) return true;
     }
     for (var x in _extensionGenerators) {
       if (x.needsFixnumImport) return true;
     }
     return false;
   }

   /// Adds dependencies of [generate] to [imports].
   ///
   /// For each .pb.dart file that the generated code needs to import,
   /// add its generator.
   void addImportsTo(
       Set<FileGenerator> imports, Set<FileGenerator> enumImports) {
     if (_fieldList == null) throw StateError("message not resolved");
     for (var field in _fieldList) {
       var typeGen = field.baseType.generator;
       if (typeGen is EnumGenerator) {
         enumImports.add(typeGen.fileGen);
       } else if (typeGen != null) {
         imports.add(typeGen.fileGen);
       }
     }
     for (var m in _messageGenerators) {
       m.addImportsTo(imports, enumImports);
     }
     for (var x in _extensionGenerators) {
       x.addImportsTo(imports, enumImports);
     }
   }

   // Returns the number of enums in this message and all nested messages.
   int get enumCount {
     var count = _enumGenerators.length;
     for (var m in _messageGenerators) {
       count += m.enumCount;
     }
     return count;
   }

   /// Adds dependencies of [generateConstants] to [imports].
   ///
   /// For each .pbjson.dart file that the generated code needs to import,
   /// add its generator.
   void addConstantImportsTo(Set<FileGenerator> imports) {
     if (_fieldList == null) throw StateError("message not resolved");
     for (var m in _messageGenerators) {
       m.addConstantImportsTo(imports);
     }
     for (var x in _extensionGenerators) {
       x.addConstantImportsTo(imports);
     }
   }

   void generate(IndentingWriter out) {
     checkResolved();

     for (MessageGenerator m in _messageGenerators) {
       // Don't output the generated map entry type. Instead, the `PbMap` type
       // from the protobuf library is used to hold the keys and values.
       if (m._descriptor.options.hasMapEntry()) continue;
       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) => '$_mixinImportPrefix.${m.name}');
       mixinClause = ' with ${mixinNames.join(", ")}';
     }

     String packageClause = package == ''
         ? ''
         : ', package: const $_protobufImportPrefix.PackageName(\'$package\')';
     String proto3JsonClause = (mixin?.hasProto3JsonHelpers ?? false)
         ? ', toProto3Json: $_mixinImportPrefix.${mixin.name}.toProto3JsonHelper, '
             'fromProto3Json: $_mixinImportPrefix.${mixin.name}.fromProto3JsonHelper'
         : '';
     out.addAnnotatedBlock(
         'class ${classname} extends $_protobufImportPrefix.GeneratedMessage${mixinClause} {',
         '}', [
       NamedLocation(
           name: classname, fieldPathSegment: fieldPath, start: 'class '.length)
     ], () {
       for (OneofNames oneof in _oneofNames) {
         out.addBlock(
             'static const $_coreImportPrefix.Map<$_coreImportPrefix.int, ${oneof.oneofEnumName}> ${oneof.byTagMapName} = {',
             '};', () {
           for (ProtobufField field in _oneofFields[oneof.index]) {
             final oneofMemberName =
                 oneofEnumMemberName(field.memberNames.fieldName);
             out.println(
                 '${field.number} : ${oneof.oneofEnumName}.${oneofMemberName},');
           }
           out.println('0 : ${oneof.oneofEnumName}.notSet');
         });
       }
       out.addBlock(
           'static final $_protobufImportPrefix.BuilderInfo _i = '
               '$_protobufImportPrefix.BuilderInfo(\'${messageName}\'$packageClause'
               ', createEmptyInstance: create'
               '$proto3JsonClause)',
           ';', () {
         for (int oneof = 0; oneof < _oneofFields.length; oneof++) {
           List<int> tags =
               _oneofFields[oneof].map((ProtobufField f) => f.number).toList();
           out.println("..oo($oneof, ${tags})");
         }

         for (ProtobufField field in _fieldList) {
           out.println(field.generateBuilderInfoCall(fileGen, package));
         }

         if (_descriptor.extensionRange.isNotEmpty) {
           out.println('..hasExtensions = true');
         }
         if (!_hasRequiredFields(this, Set())) {
           out.println('..hasRequiredFields = false');
         }
       });

       for (ExtensionGenerator x in _extensionGenerators) {
         x.generate(out);
       }

       out.println();

       out.printlnAnnotated('${classname}._() : super();', [
         NamedLocation(name: classname, fieldPathSegment: fieldPath, start: 0)
       ]);
       out.println('factory ${classname}() => create();');
       out.println(
           'factory ${classname}.fromBuffer($_coreImportPrefix.List<$_coreImportPrefix.int> i,'
           ' [$_protobufImportPrefix.ExtensionRegistry r = $_protobufImportPrefix.ExtensionRegistry.EMPTY])'
           ' => create()..mergeFromBuffer(i, r);');
       out.println('factory ${classname}.fromJson($_coreImportPrefix.String i,'
           ' [$_protobufImportPrefix.ExtensionRegistry r = $_protobufImportPrefix.ExtensionRegistry.EMPTY])'
           ' => create()..mergeFromJson(i, r);');
       out.println('${classname} clone() =>'
           ' ${classname}()..mergeFromMessage(this);');
       out.println('$classname copyWith(void Function($classname) updates) =>'
           ' super.copyWith((message) => updates(message as $classname));');

       out.println('$_protobufImportPrefix.BuilderInfo get info_ => _i;');

       // Factory functions which can be used as default value closures.
       out.println("@${_coreImportPrefix}.pragma('dart2js:noInline')");
       out.println('static ${classname} create() => ${classname}._();');
       out.println('${classname} createEmptyInstance() => create();');

       out.println(
           'static $_protobufImportPrefix.PbList<${classname}> createRepeated() =>'
           ' $_protobufImportPrefix.PbList<${classname}>();');
       out.println("@${_coreImportPrefix}.pragma('dart2js:noInline')");
       out.println('static ${classname} getDefault() =>'
           ' _defaultInstance ??='
           ' $_protobufImportPrefix.GeneratedMessage.\$_defaultFor<${classname}>'
           '(create);');
       out.println('static ${classname} _defaultInstance;');

       generateFieldsAccessorsMutators(out);
       mixin?.injectHelpers(out);
     });
     out.println();
   }

   // Returns true if the message type has any required fields.  If it doesn't,
   // we can optimize out calls to its isInitialized()/_findInvalidFields()
   // methods.
   //
   // already_seen is used to avoid checking the same type multiple times
   // (and also to protect against unbounded recursion).
   bool _hasRequiredFields(MessageGenerator type, Set alreadySeen) {
     if (type._fieldList == null) throw StateError("message not resolved");

     if (alreadySeen.contains(type.fullName)) {
       // The type is already in cache.  This means that either:
       // a. The type has no required fields.
       // b. We are in the midst of checking if the type has required fields,
       //    somewhere up the stack.  In this case, we know that if the type
       //    has any required fields, they'll be found when we return to it,
       //    and the whole call to HasRequiredFields() will return true.
       //    Therefore, we don't have to check if this type has required fields
       //    here.
       return false;
     }
     alreadySeen.add(type.fullName);
     // If the type has extensions, an extension with message type could contain
     // required fields, so we have to be conservative and assume such an
     // extension exists.
     if (type._descriptor.extensionRange.isNotEmpty) {
       return true;
     }

     for (ProtobufField field in type._fieldList) {
       if (field.isRequired) {
         return true;
       }
       if (field.baseType.isMessage) {
         MessageGenerator child = field.baseType.generator;
         if (_hasRequiredFields(child, alreadySeen)) {
           return true;
         }
       }
     }
     return false;
   }

   void generateFieldsAccessorsMutators(IndentingWriter out) {
     _oneofNames
         .forEach((OneofNames oneof) => generateOneofAccessors(out, oneof));

     for (var field in _fieldList) {
       out.println();
       List<int> memberFieldPath = List.from(fieldPath)
         ..addAll([_messageFieldTag, field.sourcePosition]);
       generateFieldAccessorsMutators(field, out, memberFieldPath);
     }
   }

   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, List<int> memberFieldPath) {
     var fieldTypeString = field.getDartType(fileGen);
     var defaultExpr = field.getDefaultExpr();
     var names = field.memberNames;

     _emitDeprecatedIf(field.isDeprecated, out);
     _emitOverrideIf(field.overridesGetter, out);
     _emitIndexAnnotation(field.number, out);
     final getterExpr = _getterExpression(fieldTypeString, field.index,
         defaultExpr, field.isRepeated, field.isMapField);
     out.printlnAnnotated(
         '${fieldTypeString} get ${names.fieldName} => ${getterExpr};', [
       NamedLocation(
           name: names.fieldName,
           fieldPathSegment: memberFieldPath,
           start: '${fieldTypeString} get '.length)
     ]);

     if (field.isRepeated) {
       if (field.overridesSetter) {
         throw 'Field ${field.fullName} cannot override a setter for '
             '${names.fieldName} because it is repeated.';
       }
       if (field.overridesHasMethod) {
         throw 'Field ${field.fullName} cannot override '
             '${names.hasMethodName}() because it is repeated.';
       }
       if (field.overridesClearMethod) {
         throw 'Field ${field.fullName} cannot override '
             '${names.clearMethodName}() because it is repeated.';
       }
     } else {
       var fastSetter = field.baseType.setter;
       _emitDeprecatedIf(field.isDeprecated, out);
       _emitOverrideIf(field.overridesSetter, out);
       _emitIndexAnnotation(field.number, out);
       if (fastSetter != null) {
         out.printlnAnnotated(
             'set ${names.fieldName}'
             '($fieldTypeString v) { '
             '$fastSetter(${field.index}, v);'
             ' }',
             [
               NamedLocation(
                   name: names.fieldName,
                   fieldPathSegment: memberFieldPath,
                   start: 'set '.length)
             ]);
       } else {
         out.printlnAnnotated(
             'set ${names.fieldName}'
             '($fieldTypeString v) { '
             'setField(${field.number}, v);'
             ' }',
             [
               NamedLocation(
                   name: names.fieldName,
                   fieldPathSegment: memberFieldPath,
                   start: 'set '.length)
             ]);
       }
       _emitDeprecatedIf(field.isDeprecated, out);
       _emitOverrideIf(field.overridesHasMethod, out);
       _emitIndexAnnotation(field.number, out);
       out.printlnAnnotated(
           '$_coreImportPrefix.bool ${names.hasMethodName}() =>'
           ' \$_has(${field.index});',
           [
             NamedLocation(
                 name: names.hasMethodName,
                 fieldPathSegment: memberFieldPath,
                 start: '$_coreImportPrefix.bool '.length)
           ]);
       _emitDeprecatedIf(field.isDeprecated, out);
       _emitOverrideIf(field.overridesClearMethod, out);
       _emitIndexAnnotation(field.number, out);
       out.printlnAnnotated(
           'void ${names.clearMethodName}() =>'
           ' clearField(${field.number});',
           [
             NamedLocation(
                 name: names.clearMethodName,
                 fieldPathSegment: memberFieldPath,
                 start: 'void '.length)
           ]);
       if (field.baseType.isMessage) {
         _emitDeprecatedIf(field.isDeprecated, out);
         _emitIndexAnnotation(field.number, out);
         out.printlnAnnotated(
             '${fieldTypeString} ${names.ensureMethodName}() => '
             '\$_ensure(${field.index});',
             <NamedLocation>[
               NamedLocation(
                   name: names.ensureMethodName,
                   fieldPathSegment: memberFieldPath,
                   start: '${fieldTypeString} '.length)
             ]);
       }
     }
   }

   String _getterExpression(String fieldType, int index, String defaultExpr,
       bool isRepeated, bool isMapField) {
     if (isMapField) {
       return '\$_getMap($index)';
     }
     if (fieldType == '$_coreImportPrefix.String') {
       if (defaultExpr == '""' || defaultExpr == "''") {
         return '\$_getSZ($index)';
       }
       return '\$_getS($index, $defaultExpr)';
     }
     if (fieldType == '$_coreImportPrefix.bool') {
       if (defaultExpr == 'false') {
         return '\$_getBF($index)';
       }
       return '\$_getB($index, $defaultExpr)';
     }
     if (fieldType == '$_coreImportPrefix.int') {
       if (defaultExpr == '0') {
         return '\$_getIZ($index)';
       }
       return '\$_getI($index, $defaultExpr)';
     }
     if (fieldType == 'Int64' && defaultExpr == 'null') {
       return '\$_getI64($index)';
     }
     if (defaultExpr == 'null') {
       return isRepeated ? '\$_getList($index)' : '\$_getN($index)';
     }
     return '\$_get($index, $defaultExpr)';
   }

   void _emitDeprecatedIf(bool condition, IndentingWriter out) {
     if (condition) {
       out.println(
           '@$_coreImportPrefix.Deprecated(\'This field is deprecated.\')');
     }
   }

   void _emitOverrideIf(bool condition, IndentingWriter out) {
     if (condition) {
       out.println('@$_coreImportPrefix.override');
     }
   }

   void _emitIndexAnnotation(int index, IndentingWriter out) {
     out.println('@$_protobufImportPrefix.TagNumber($index)');
   }

   void generateEnums(IndentingWriter out) {
     for (EnumGenerator e in _enumGenerators) {
       e.generate(out);
     }

     for (MessageGenerator m in _messageGenerators) {
       m.generateEnums(out);
     }
   }

   /// Writes a Dart constant containing the JSON for the ProtoDescriptor.
   /// Also writes a separate constant for each nested message,
   /// to avoid duplication.
   void generateConstants(IndentingWriter out) {
     const nestedTypeTag = 3;
     const enumTypeTag = 4;
     assert(_descriptor.info_.fieldInfo[nestedTypeTag].name == "nestedType");
     assert(_descriptor.info_.fieldInfo[enumTypeTag].name == "enumType");

     var name = getJsonConstant(fileGen);
     var json = _descriptor.writeToJsonMap();
     var nestedTypeNames =
         _messageGenerators.map((m) => m.getJsonConstant(fileGen)).toList();
     var nestedEnumNames =
         _enumGenerators.map((e) => e.getJsonConstant(fileGen)).toList();

     out.addBlock("const $name = const {", "};", () {
       for (var key in json.keys) {
         out.print("'$key': ");
         if (key == "$nestedTypeTag") {
           // refer to message constants by name instead of repeating each value
           out.println("const [${nestedTypeNames.join(", ")}],");
           continue;
         } else if (key == "$enumTypeTag") {
           // refer to enum constants by name
           out.println("const [${nestedEnumNames.join(", ")}],");
           continue;
         }
         writeJsonConst(out, json[key]);
         out.println(",");
       }
     });
     out.println();

     for (var m in _messageGenerators) {
       m.generateConstants(out);
     }

     for (var e in _enumGenerators) {
       e.generateConstants(out);
     }
   }

   /// Returns the mixin for this message, or null if none.
   ///
   /// First searches [wellKnownMixins], then [declaredMixins],
   /// then internal mixins declared by [findMixin].
   PbMixin _getMixin(Map<String, PbMixin> declaredMixins, PbMixin defaultMixin) {
     PbMixin wellKnownMixin = wellKnownMixinForFullName(fullName);
     if (wellKnownMixin != null) return wellKnownMixin;
     if (!_descriptor.hasOptions() ||
         !_descriptor.options.hasExtension(Dart_options.mixin)) {
       return defaultMixin;
     }

     String name = _descriptor.options.getExtension(Dart_options.mixin);
     if (name.isEmpty) return null; // don't use any mixins (override default)
     var mixin = declaredMixins[name] ?? findMixin(name);
     if (mixin == null) {
       throw '${_descriptor.name} in ${_parent.fileGen.descriptor.name}: mixin "$name" not found';
     }
     return mixin;
   }
 }
	// 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;

	/// Generates the Dart enum corresponding to a oneof declaration.
	///
	/// The enum is used to represent the state of a oneof when using the
	/// corresponding which-method.
	class OneofEnumGenerator {
	static void generate(
	IndentingWriter out, String classname, List<ProtobufField> fields) {
	out.addBlock('enum ${classname} {', '}\n', () {
	for (ProtobufField field in fields) {
	final name = oneofEnumMemberName(field.memberNames.fieldName);
	out.println('$name, ');
	}
	out.println('notSet');
	});
	}
	}

	class MessageGenerator extends ProtobufContainer {
	/// The name of the Dart class to generate.
	final String classname;

	/// The fully-qualified name of the message (without any leading '.').
	final String fullName;

	/// The part of the fully qualified name that comes after the package prefix.
	///
	/// For nested messages this will include the names of the parents.
	///
	/// For example:
	/// ```
	/// package foo;
	///
	/// message Container {
	/// message Nested {
	/// int32 int32_value = 1;
	/// }
	/// }
	/// ```
	/// The nested message will have a `fullName` of 'foo.Container.Nested', and a
	/// `messageName` of 'Container.Nested'.
	String get messageName =>
	fullName.substring(package.isEmpty ? 0 : package.length + 1);

	PbMixin mixin;

	final ProtobufContainer _parent;
	final DescriptorProto _descriptor;
	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;

	List<int> _fieldPath;
	final List<int> _fieldPathSegment;

	/// See [[ProtobufContainer]
	List<int> get fieldPath =>
	_fieldPath ??= List.from(_parent.fieldPath)..addAll(_fieldPathSegment);

	// populated by resolve()
	List<ProtobufField> _fieldList;

	Set<String> _usedTopLevelNames;

	MessageGenerator._(
	DescriptorProto descriptor,
	ProtobufContainer parent,
	Map<String, PbMixin> declaredMixins,
	PbMixin defaultMixin,
	this._usedTopLevelNames,
	int repeatedFieldIndex,
	int fieldIdTag)
	: _descriptor = descriptor,
	_parent = parent,
	_fieldPathSegment = [fieldIdTag, repeatedFieldIndex],
	classname = messageOrEnumClassName(descriptor.name, _usedTopLevelNames,
	parent: parent?.classname ?? ''),
	assert(parent != null),
	fullName = parent.fullName == ''
	? descriptor.name
	: '${parent.fullName}.${descriptor.name}',
	_oneofFields =
	List.generate(descriptor.oneofDecl.length, (int index) => []) {
	mixin = _getMixin(declaredMixins, defaultMixin);
	for (var i = 0; i < _descriptor.enumType.length; i++) {
	EnumDescriptorProto e = _descriptor.enumType[i];
	_enumGenerators.add(EnumGenerator.nested(e, this, _usedTopLevelNames, i));
	}

	for (var i = 0; i < _descriptor.nestedType.length; i++) {
	DescriptorProto n = _descriptor.nestedType[i];
	_messageGenerators.add(MessageGenerator.nested(
	n, this, declaredMixins, defaultMixin, _usedTopLevelNames, i));
	}

	// Extensions within messages won't create top-level classes and don't need
	// to check against / be added to top-level reserved names.
	final usedExtensionNames = Set<String>()..addAll(forbiddenExtensionNames);
	for (var i = 0; i < _descriptor.extension.length; i++) {
	FieldDescriptorProto x = _descriptor.extension[i];
	_extensionGenerators
	.add(ExtensionGenerator.nested(x, this, usedExtensionNames, i));
	}
	}

	static const _topLevelMessageTag = 4;
	static const _nestedMessageTag = 3;
	static const _messageFieldTag = 2;

	MessageGenerator.topLevel(
	DescriptorProto descriptor,
	ProtobufContainer parent,
	Map<String, PbMixin> declaredMixins,
	PbMixin defaultMixin,
	Set<String> usedNames,
	int repeatedFieldIndex)
	: this._(descriptor, parent, declaredMixins, defaultMixin, usedNames,
	repeatedFieldIndex, _topLevelMessageTag);

	MessageGenerator.nested(
	DescriptorProto descriptor,
	ProtobufContainer parent,
	Map<String, PbMixin> declaredMixins,
	PbMixin defaultMixin,
	Set<String> usedNames,
	int repeatedFieldIndex)
	: this._(descriptor, parent, declaredMixins, defaultMixin, usedNames,
	repeatedFieldIndex, _nestedMessageTag);

	String get package => _parent.package;

	/// The generator of the .pb.dart file that will declare this type.
	FileGenerator get fileGen => _parent.fileGen;

	/// Throws an exception if [resolve] hasn't been called yet.
	void checkResolved() {
	if (_fieldList == null) {
	throw StateError("message not resolved: ${fullName}");
	}
	}

	/// Returns a const expression that evaluates to the JSON for this message.
	/// [usage] represents the .pb.dart file where the expression will be used.
	String getJsonConstant(FileGenerator usage) {
	var name = "$classname\$json";
	if (usage.protoFileUri == fileGen.protoFileUri) {
	return name;
	}
	return "$fileImportPrefix.$name";
	}

	/// Adds all mixins used in this message and any submessages.
	void addMixinsTo(Set<PbMixin> output) {
	if (mixin != null) {
	output.addAll(mixin.findMixinsToApply());
	}
	for (var m in _messageGenerators) {
	m.addMixinsTo(output);
	}
	}

	// Registers message and enum types that can be used elsewhere.
	void register(GenerationContext ctx) {
	ctx.registerFieldType(this);
	for (var m in _messageGenerators) {
	m.register(ctx);
	}
	for (var e in _enumGenerators) {
	e.register(ctx);
	}
	}

	// Creates fields and resolves extension targets.
	void resolve(GenerationContext ctx) {
	if (_fieldList != null) throw StateError("message already resolved");

	var reserved = mixin?.findReservedNames() ?? const <String>[];
	MemberNames members = messageMemberNames(
	_descriptor, classname, _usedTopLevelNames,
	reserved: reserved);

	_fieldList = <ProtobufField>[];
	for (FieldNames names in members.fieldNames) {
	ProtobufField field = 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);
	}
	for (var x in _extensionGenerators) {
	x.resolve(ctx);
	}
	}

	bool get needsFixnumImport {
	if (_fieldList == null) throw StateError("message not resolved");
	for (var field in _fieldList) {
	if (field.needsFixnumImport) return true;
	}
	for (var m in _messageGenerators) {
	if (m.needsFixnumImport) return true;
	}
	for (var x in _extensionGenerators) {
	if (x.needsFixnumImport) return true;
	}
	return false;
	}

	/// Adds dependencies of [generate] to [imports].
	///
	/// For each .pb.dart file that the generated code needs to import,
	/// add its generator.
	void addImportsTo(
	Set<FileGenerator> imports, Set<FileGenerator> enumImports) {
	if (_fieldList == null) throw StateError("message not resolved");
	for (var field in _fieldList) {
	var typeGen = field.baseType.generator;
	if (typeGen is EnumGenerator) {
	enumImports.add(typeGen.fileGen);
	} else if (typeGen != null) {
	imports.add(typeGen.fileGen);
	}
	}
	for (var m in _messageGenerators) {
	m.addImportsTo(imports, enumImports);
	}
	for (var x in _extensionGenerators) {
	x.addImportsTo(imports, enumImports);
	}
	}

	// Returns the number of enums in this message and all nested messages.
	int get enumCount {
	var count = _enumGenerators.length;
	for (var m in _messageGenerators) {
	count += m.enumCount;
	}
	return count;
	}

	/// Adds dependencies of [generateConstants] to [imports].
	///
	/// For each .pbjson.dart file that the generated code needs to import,
	/// add its generator.
	void addConstantImportsTo(Set<FileGenerator> imports) {
	if (_fieldList == null) throw StateError("message not resolved");
	for (var m in _messageGenerators) {
	m.addConstantImportsTo(imports);
	}
	for (var x in _extensionGenerators) {
	x.addConstantImportsTo(imports);
	}
	}

	void generate(IndentingWriter out) {
	checkResolved();

	for (MessageGenerator m in _messageGenerators) {
	// Don't output the generated map entry type. Instead, the `PbMap` type
	// from the protobuf library is used to hold the keys and values.
	if (m._descriptor.options.hasMapEntry()) continue;
	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) => '$_mixinImportPrefix.${m.name}');
	mixinClause = ' with ${mixinNames.join(", ")}';
	}

	String packageClause = package == ''
	? ''
	: ', package: const $_protobufImportPrefix.PackageName(\'$package\')';
	String proto3JsonClause = (mixin?.hasProto3JsonHelpers ?? false)
	? ', toProto3Json: $_mixinImportPrefix.${mixin.name}.toProto3JsonHelper, '
	'fromProto3Json: $_mixinImportPrefix.${mixin.name}.fromProto3JsonHelper'
	: '';
	out.addAnnotatedBlock(
	'class ${classname} extends $_protobufImportPrefix.GeneratedMessage${mixinClause} {',
	'}', [
	NamedLocation(
	name: classname, fieldPathSegment: fieldPath, start: 'class '.length)
	], () {
	for (OneofNames oneof in _oneofNames) {
	out.addBlock(
	'static const $_coreImportPrefix.Map<$_coreImportPrefix.int, ${oneof.oneofEnumName}> ${oneof.byTagMapName} = {',
	'};', () {
	for (ProtobufField field in _oneofFields[oneof.index]) {
	final oneofMemberName =
	oneofEnumMemberName(field.memberNames.fieldName);
	out.println(
	'${field.number} : ${oneof.oneofEnumName}.${oneofMemberName},');
	}
	out.println('0 : ${oneof.oneofEnumName}.notSet');
	});
	}
	out.addBlock(
	'static final $_protobufImportPrefix.BuilderInfo _i = '
	'$_protobufImportPrefix.BuilderInfo(\'${messageName}\'$packageClause'
	', createEmptyInstance: create'
	'$proto3JsonClause)',
	';', () {
	for (int oneof = 0; oneof < _oneofFields.length; oneof++) {
	List<int> tags =
	_oneofFields[oneof].map((ProtobufField f) => f.number).toList();
	out.println("..oo($oneof, ${tags})");
	}

	for (ProtobufField field in _fieldList) {
	out.println(field.generateBuilderInfoCall(fileGen, package));
	}

	if (_descriptor.extensionRange.isNotEmpty) {
	out.println('..hasExtensions = true');
	}
	if (!_hasRequiredFields(this, Set())) {
	out.println('..hasRequiredFields = false');
	}
	});

	for (ExtensionGenerator x in _extensionGenerators) {
	x.generate(out);
	}

	out.println();

	out.printlnAnnotated('${classname}._() : super();', [
	NamedLocation(name: classname, fieldPathSegment: fieldPath, start: 0)
	]);
	out.println('factory ${classname}() => create();');
	out.println(
	'factory ${classname}.fromBuffer($_coreImportPrefix.List<$_coreImportPrefix.int> i,'
	' [$_protobufImportPrefix.ExtensionRegistry r = $_protobufImportPrefix.ExtensionRegistry.EMPTY])'
	' => create()..mergeFromBuffer(i, r);');
	out.println('factory ${classname}.fromJson($_coreImportPrefix.String i,'
	' [$_protobufImportPrefix.ExtensionRegistry r = $_protobufImportPrefix.ExtensionRegistry.EMPTY])'
	' => create()..mergeFromJson(i, r);');
	out.println('${classname} clone() =>'
	' ${classname}()..mergeFromMessage(this);');
	out.println('$classname copyWith(void Function($classname) updates) =>'
	' super.copyWith((message) => updates(message as $classname));');

	out.println('$_protobufImportPrefix.BuilderInfo get info_ => _i;');

	// Factory functions which can be used as default value closures.
	out.println("@${_coreImportPrefix}.pragma('dart2js:noInline')");
	out.println('static ${classname} create() => ${classname}._();');
	out.println('${classname} createEmptyInstance() => create();');

	out.println(
	'static $_protobufImportPrefix.PbList<${classname}> createRepeated() =>'
	' $_protobufImportPrefix.PbList<${classname}>();');
	out.println("@${_coreImportPrefix}.pragma('dart2js:noInline')");
	out.println('static ${classname} getDefault() =>'
	' _defaultInstance ??='
	' $_protobufImportPrefix.GeneratedMessage.\$_defaultFor<${classname}>'
	'(create);');
	out.println('static ${classname} _defaultInstance;');

	generateFieldsAccessorsMutators(out);
	mixin?.injectHelpers(out);
	});
	out.println();
	}

	// Returns true if the message type has any required fields. If it doesn't,
	// we can optimize out calls to its isInitialized()/_findInvalidFields()
	// methods.
	//
	// already_seen is used to avoid checking the same type multiple times
	// (and also to protect against unbounded recursion).
	bool _hasRequiredFields(MessageGenerator type, Set alreadySeen) {
	if (type._fieldList == null) throw StateError("message not resolved");

	if (alreadySeen.contains(type.fullName)) {
	// The type is already in cache. This means that either:
	// a. The type has no required fields.
	// b. We are in the midst of checking if the type has required fields,
	// somewhere up the stack. In this case, we know that if the type
	// has any required fields, they'll be found when we return to it,
	// and the whole call to HasRequiredFields() will return true.
	// Therefore, we don't have to check if this type has required fields
	// here.
	return false;
	}
	alreadySeen.add(type.fullName);
	// If the type has extensions, an extension with message type could contain
	// required fields, so we have to be conservative and assume such an
	// extension exists.
	if (type._descriptor.extensionRange.isNotEmpty) {
	return true;
	}

	for (ProtobufField field in type._fieldList) {
	if (field.isRequired) {
	return true;
	}
	if (field.baseType.isMessage) {
	MessageGenerator child = field.baseType.generator;
	if (_hasRequiredFields(child, alreadySeen)) {
	return true;
	}
	}
	}
	return false;
	}

	void generateFieldsAccessorsMutators(IndentingWriter out) {
	_oneofNames
	.forEach((OneofNames oneof) => generateOneofAccessors(out, oneof));

	for (var field in _fieldList) {
	out.println();
	List<int> memberFieldPath = List.from(fieldPath)
	..addAll([_messageFieldTag, field.sourcePosition]);
	generateFieldAccessorsMutators(field, out, memberFieldPath);
	}
	}

	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, List<int> memberFieldPath) {
	var fieldTypeString = field.getDartType(fileGen);
	var defaultExpr = field.getDefaultExpr();
	var names = field.memberNames;

	_emitDeprecatedIf(field.isDeprecated, out);
	_emitOverrideIf(field.overridesGetter, out);
	_emitIndexAnnotation(field.number, out);
	final getterExpr = _getterExpression(fieldTypeString, field.index,
	defaultExpr, field.isRepeated, field.isMapField);
	out.printlnAnnotated(
	'${fieldTypeString} get ${names.fieldName} => ${getterExpr};', [
	NamedLocation(
	name: names.fieldName,
	fieldPathSegment: memberFieldPath,
	start: '${fieldTypeString} get '.length)
	]);

	if (field.isRepeated) {
	if (field.overridesSetter) {
	throw 'Field ${field.fullName} cannot override a setter for '
	'${names.fieldName} because it is repeated.';
	}
	if (field.overridesHasMethod) {
	throw 'Field ${field.fullName} cannot override '
	'${names.hasMethodName}() because it is repeated.';
	}
	if (field.overridesClearMethod) {
	throw 'Field ${field.fullName} cannot override '
	'${names.clearMethodName}() because it is repeated.';
	}
	} else {
	var fastSetter = field.baseType.setter;
	_emitDeprecatedIf(field.isDeprecated, out);
	_emitOverrideIf(field.overridesSetter, out);
	_emitIndexAnnotation(field.number, out);
	if (fastSetter != null) {
	out.printlnAnnotated(
	'set ${names.fieldName}'
	'($fieldTypeString v) { '
	'$fastSetter(${field.index}, v);'
	' }',
	[
	NamedLocation(
	name: names.fieldName,
	fieldPathSegment: memberFieldPath,
	start: 'set '.length)
	]);
	} else {
	out.printlnAnnotated(
	'set ${names.fieldName}'
	'($fieldTypeString v) { '
	'setField(${field.number}, v);'
	' }',
	[
	NamedLocation(
	name: names.fieldName,
	fieldPathSegment: memberFieldPath,
	start: 'set '.length)
	]);
	}
	_emitDeprecatedIf(field.isDeprecated, out);
	_emitOverrideIf(field.overridesHasMethod, out);
	_emitIndexAnnotation(field.number, out);
	out.printlnAnnotated(
	'$_coreImportPrefix.bool ${names.hasMethodName}() =>'
	' \$_has(${field.index});',
	[
	NamedLocation(
	name: names.hasMethodName,
	fieldPathSegment: memberFieldPath,
	start: '$_coreImportPrefix.bool '.length)
	]);
	_emitDeprecatedIf(field.isDeprecated, out);
	_emitOverrideIf(field.overridesClearMethod, out);
	_emitIndexAnnotation(field.number, out);
	out.printlnAnnotated(
	'void ${names.clearMethodName}() =>'
	' clearField(${field.number});',
	[
	NamedLocation(
	name: names.clearMethodName,
	fieldPathSegment: memberFieldPath,
	start: 'void '.length)
	]);
	if (field.baseType.isMessage) {
	_emitDeprecatedIf(field.isDeprecated, out);
	_emitIndexAnnotation(field.number, out);
	out.printlnAnnotated(
	'${fieldTypeString} ${names.ensureMethodName}() => '
	'\$_ensure(${field.index});',
	<NamedLocation>[
	NamedLocation(
	name: names.ensureMethodName,
	fieldPathSegment: memberFieldPath,
	start: '${fieldTypeString} '.length)
	]);
	}
	}
	}

	String _getterExpression(String fieldType, int index, String defaultExpr,
	bool isRepeated, bool isMapField) {
	if (isMapField) {
	return '\$_getMap($index)';
	}
	if (fieldType == '$_coreImportPrefix.String') {
	if (defaultExpr == '""' \|\| defaultExpr == "''") {
	return '\$_getSZ($index)';
	}
	return '\$_getS($index, $defaultExpr)';
	}
	if (fieldType == '$_coreImportPrefix.bool') {
	if (defaultExpr == 'false') {
	return '\$_getBF($index)';
	}
	return '\$_getB($index, $defaultExpr)';
	}
	if (fieldType == '$_coreImportPrefix.int') {
	if (defaultExpr == '0') {
	return '\$_getIZ($index)';
	}
	return '\$_getI($index, $defaultExpr)';
	}
	if (fieldType == 'Int64' && defaultExpr == 'null') {
	return '\$_getI64($index)';
	}
	if (defaultExpr == 'null') {
	return isRepeated ? '\$_getList($index)' : '\$_getN($index)';
	}
	return '\$_get($index, $defaultExpr)';
	}

	void _emitDeprecatedIf(bool condition, IndentingWriter out) {
	if (condition) {
	out.println(
	'@$_coreImportPrefix.Deprecated(\'This field is deprecated.\')');
	}
	}

	void _emitOverrideIf(bool condition, IndentingWriter out) {
	if (condition) {
	out.println('@$_coreImportPrefix.override');
	}
	}

	void _emitIndexAnnotation(int index, IndentingWriter out) {
	out.println('@$_protobufImportPrefix.TagNumber($index)');
	}

	void generateEnums(IndentingWriter out) {
	for (EnumGenerator e in _enumGenerators) {
	e.generate(out);
	}

	for (MessageGenerator m in _messageGenerators) {
	m.generateEnums(out);
	}
	}

	/// Writes a Dart constant containing the JSON for the ProtoDescriptor.
	/// Also writes a separate constant for each nested message,
	/// to avoid duplication.
	void generateConstants(IndentingWriter out) {
	const nestedTypeTag = 3;
	const enumTypeTag = 4;
	assert(_descriptor.info_.fieldInfo[nestedTypeTag].name == "nestedType");
	assert(_descriptor.info_.fieldInfo[enumTypeTag].name == "enumType");

	var name = getJsonConstant(fileGen);
	var json = _descriptor.writeToJsonMap();
	var nestedTypeNames =
	_messageGenerators.map((m) => m.getJsonConstant(fileGen)).toList();
	var nestedEnumNames =
	_enumGenerators.map((e) => e.getJsonConstant(fileGen)).toList();

	out.addBlock("const $name = const {", "};", () {
	for (var key in json.keys) {
	out.print("'$key': ");
	if (key == "$nestedTypeTag") {
	// refer to message constants by name instead of repeating each value
	out.println("const [${nestedTypeNames.join(", ")}],");
	continue;
	} else if (key == "$enumTypeTag") {
	// refer to enum constants by name
	out.println("const [${nestedEnumNames.join(", ")}],");
	continue;
	}
	writeJsonConst(out, json[key]);
	out.println(",");
	}
	});
	out.println();

	for (var m in _messageGenerators) {
	m.generateConstants(out);
	}

	for (var e in _enumGenerators) {
	e.generateConstants(out);
	}
	}

	/// Returns the mixin for this message, or null if none.
	///
	/// First searches [wellKnownMixins], then [declaredMixins],
	/// then internal mixins declared by [findMixin].
	PbMixin _getMixin(Map<String, PbMixin> declaredMixins, PbMixin defaultMixin) {
	PbMixin wellKnownMixin = wellKnownMixinForFullName(fullName);
	if (wellKnownMixin != null) return wellKnownMixin;
	if (!_descriptor.hasOptions() \|\|
	!_descriptor.options.hasExtension(Dart_options.mixin)) {
	return defaultMixin;
	}

	String name = _descriptor.options.getExtension(Dart_options.mixin);
	if (name.isEmpty) return null; // don't use any mixins (override default)
	var mixin = declaredMixins[name] ?? findMixin(name);
	if (mixin == null) {
	throw '${_descriptor.name} in ${_parent.fileGen.descriptor.name}: mixin "$name" not found';
	}
	return mixin;
	}
	}