code_builder

A fluent, builder-based library for generating valid Dart code.

Basic Usage

code_builder has a narrow and user-friendly API.

Most Dart syntax structures are created using builders. For example, an empty class:

import 'package:code_builder/code_builder.dart';

void main() {
  final animal = Class((builder) => builder
      ..name = 'Animal'
      ..extend = refer('Organism')
  );
  // ...
}

Will produce:

class Animal extends Organism {}

Then use a DartEmitter and the accept method to build the code_builder structures into valid Dart code. For example:

import 'package:code_builder/code_builder.dart';
import 'package:dart_style/dart_style.dart';

void main() {
  // ...

  final emitter = DartEmitter();

  // Generate code for 'animal' into a new StringBuffer
  final StringSink result = animal.accept(emitter);

  // or, add it to an existing one
  final buffer = StringBuffer();
  animal.accept(emitter, buffer);

  // format the output using package:dart_style
  final String formatted = DartFormatter(
    languageVersion: DartFormatter.latestLanguageVersion,
  ).format(result.toString());

  // voilà
  print(formatted);
}

Will output the code from above.

For more usage examples see the example and test folders.

Automatic Scoping

Have a complicated set of dependencies for your generated code? code_builder supports automatic scoping of your ASTs to automatically use prefixes to avoid symbol conflicts:

import 'package:code_builder/code_builder.dart';
import 'package:dart_style/dart_style.dart';

void main() {
  final library = Library((b) => b.body.addAll([
        Method((b) => b
          ..body = const Code('')
          ..name = 'doThing'
          ..returns = refer('Thing', 'package:a/a.dart')),
        Method((b) => b
          ..body = const Code('')
          ..name = 'doOther'
          ..returns = refer('Other', 'package:b/b.dart')),
      ]));

  // use a scoped DartEmitter to enable automatic prefixing
  // using Allocator.simplePrefixing
  final emitter = DartEmitter.scoped();

  final formatted = DartFormatter(
    languageVersion: DartFormatter.latestLanguageVersion)
        .format(library.accept(emitter).toString());

  print(formatted);
}

Will output:

import 'package:a/a.dart' as _i1;
import 'package:b/b.dart' as _i2;

_i1.Thing doThing() {}
_i2.Other doOther() {}

Contributing

• Read and help us document common patterns over in the docs.
• Is there a bug in the code? File an issue.

If a feature is missing (the Dart language is always evolving) or you'd like an easier or better way to do something, consider opening a pull request. You can always file an issue, but generally speaking, feature requests will be on a best-effort basis.

NOTE: Due to the evolving Dart SDK the local dartfmt must be used to format this repository. You can run it simply from the command-line:

dart run dart_style:format -w .

Updating generated (.g.dart) files

NOTE: There is currently a limitation in build_runner that requires a workaround for developing this package since it is a dependency of the build system.

Make a snapshot of the generated build_runner build script and run from the snapshot instead of from source to avoid problems with deleted files. These steps must be run without deleting the source files.

./tool/regenerate.sh