LibraryBuilder should allow more customized build extensions

[Vildnex]

• Dart SDK Version: Dart SDK version: 3.2.1 (stable) (None) on "linux_x64"
• What package(s) from this repo you are using, and the version:
  • build 2.4.1
  • source_gen 1.4.0
  • build_runner 2.4.6
• What builder(s) you are using (or writing yourself). Try to give a short summary of what they do: Summary: I am trying to build a builder that is going to generate some files into a custom folder instead of them to be next to the source folder.

Current folder project structure after running that command:

├── lib
│   ├── entity_generator.dart
│   └── test_files
│       ├── annotation
│       │   └── annotation.dart
│       ├── classes2.dart
│       ├── classes2.entity.dart
│       ├── classes.dart
│       ├── classes.entity.dart
│       └── gen
├── pubspec.lock
└── pubspec.yaml

Current folder project structure after generating them into the custom folder:

├── lib
│   ├── entity_generator.dart
│   └── test_files
│       ├── annotation
│       │   └── annotation.dart
│       ├── classes2.dart
│       ├── classes.dart
│       └── gen
│           ├── classes.entity.dart
|           └── classes2.entity.dart
├── pubspec.lock
└── pubspec.yaml

entity_generator.dart:

class EntityGenerator extends GeneratorForAnnotation<Entity> {
  @override
  generateForAnnotatedElement(Element element, ConstantReader annotation, BuildStep buildStep) {
    if (element is! ClassElement) {
      throw InvalidGenerationSourceError('`@Entity` can only be used on classes.', element: element);
    }

    final className = element.displayName;
    final buffer = StringBuffer();

    // Generate the class with entity exports
    buffer.writeln('class $className extends Entity {}');
    return buffer.toString();
  }
}

Builder entityBuilder(BuilderOptions options) => LibraryBuilder(EntityGenerator(), generatedExtension: '.entity.dart');

build.yaml:

    targets:
      $default:
        builders:
          test_app|export_locating_builder:
            enabled: true

    builders:
      export_locating_builder:
        import: "package:test_app/entity_generator.dart"
        builder_factories: [ "entityBuilder" ]
        build_extensions: {
          '^lib/test_files/{{}}.dart': ['lib/test_files/gen/{{}}.entity.dart']
        }
        auto_apply: dependents
        build_to: source

For the moment even if I did the part {{}} the files will still be generated next to the original class instead of the gen folder.

• Whether you are using Windows, MacOSX, or Linux (if applicable): Linux
• Whether you are using Chrome, Safari, Firefox, Edge (if applicable): Not applicable
• Any other packages or constraints we should know about None

Sources that I've checked already:

• https://github.com/dart-lang/build/issues/3475
• https://github.com/dart-lang/build/blob/master/docs/writing_a_builder.md#capture-groups
• https://simonbinder.eu/posts/build_directory_moves/

[jakemac53]

If you run dart run build_runner doctor I think it will highlight the issue, which is a mismatch in build extensions (the build extension in your build.yaml isn't what the actual builder is declaring, and the latter is what is actually used).

I don't believe that LibraryBuilder allows you to configure the extensions in such a way that you could support this, ~but its worth filing an issue on the source_gen package to ask for it?~ (I just transferred the issue here).

[jakemac53]

Essentially the core of the issue is that LibraryBuilder only allows you to configure the output extensions part of build extensions, and not the input extension (which is hardcoded to .dart). You would need to configure both.

[Vildnex]

@jakemac53, the output of the dart run build_runner doctor is [WARNING] Builder test_app:export_locating_builder uses input extension .dart which is not specified in the 'build.yaml' but I am not entirely sure how to fix it. So basically because the LibraryBuilder does not have support for this, what other Builder should I use? Or there is no other way to do this except building my own Builder?

[jakemac53]

Or there is no other way to do this except building my own Builder?

Essentially this, the source_gen package is pretty opinionated today about output extensions. Afaik it does this somewhat in order to simplify some of the things it does (such as checking that the user included the appropriate part file, where relevant).

[jakemac53]

You can fwiw re-use some of the utilities provided by this package to help create the builder though.

[Vildnex]

I see, alright then thanks for clarify this