source_gen

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Highly experimental. Expect breaking changes.

source_gen provides:

• A tool for generating code that is part of your Dart project.
• A framework for creating and using multiple code generators in a single project.
• A convention for human and tool generated Dart code to coexist with clean separation.

Example

Given a library example.dart:

library source_gen.example.example;

import 'package:source_gen/generators/json_serializable.dart';

part 'example.g.dart';

@JsonSerializable()
class Person extends Object with _$PersonSerializerMixin {
  final String firstName, middleName, lastName;
  final DateTime dateOfBirth;

  Person(this.firstName, this.lastName, {this.middleName, this.dateOfBirth});

  factory Person.fromJson(json) => _$PersonFromJson(json);
}

source_gen creates the corresponding part example.g.dart:

part of source_gen.example.example;

// **************************************************************************
// Generator: JsonGenerator
// Target: class Person
// **************************************************************************

Person _$PersonFromJson(Map<String, Object> json) => new Person(
    json['firstName'], json['lastName'],
    middleName: json['middleName'],
    dateOfBirth: json.containsKey('dateOfBirth')
        ? DateTime.parse(json['dateOfBirth'])
        : null);

abstract class _$PersonSerializerMixin {
  String get firstName;
  String get middleName;
  String get lastName;
  DateTime get dateOfBirth;
  Map<String, Object> toJson() => {
    'firstName': firstName,
    'middleName': middleName,
    'lastName': lastName,
    'dateOfBirth': dateOfBirth == null ? null : dateOfBirth.toIso8601String()
  };
}

See the example code in the source_gen GitHub repo.

Creating a generator

Extend the Generator class to plug into source_gen.

• Trivial example
• Included generators

Running generators

Create a script that invokes the generate method.

Alternatively, you can create a build.dart file which calls the build method. You can use the build_system package to enjoy this automatic workflow.

Note: The original design was meant to work with the Dart Editor build system. Dart Editor is unsupported as of Dart 1.11.

See build.dart in the repository for an example.

source_gen vs Dart Transformers

Dart Transformers are often used to create and modify code and assets as part of a Dart project.

Transformers allow modification of existing code and encapsulates changes by having developers use pub commands – run, serve, and build.

source_gen provides a different model. Code is generated and updated as part of a project. It is designed to create part files that augment developer maintained Dart libraries.

Generated code MAY be checked in as part of our project source, although the decision may vary depending on project needs.

Generated code SHOULD be included when publishing a project as a pub package. The fact that source_gen is used in a package is an implementation detail.