Add lean_builder support infrastructure to retrofit_generator

README.md

@@ -64,8 +64,24 @@ then run the generator
 ```sh
 # dart
 dart pub run build_runner build
+
+# for watch mode (recommended during development)
+dart pub run build_runner watch
 ```
 
+#### Lean Builder Support (Experimental)
+
+Retrofit now has experimental support for [lean_builder](https://pub.dev/packages/lean_builder), a faster build system for Dart. While lean_builder support is still under development, the infrastructure has been added for future use.
+
+To prepare for lean_builder support, add it to your `dev_dependencies`:
+
+```yaml
+dev_dependencies:
+  lean_builder: ^0.1.2
+```
+
+**Note:** For now, please continue using `build_runner` as shown above. Full lean_builder integration will be available in a future release once lean_builder reaches stability.
+
 ### Use it
 
 ```dart

example/LEAN_BUILDER.md

@@ -0,0 +1,102 @@
+# Lean Builder Support (Experimental)
+
+This document provides information about using lean_builder with retrofit_generator.
+
+## Status
+
+⚠️ **Experimental** - Lean Builder support is currently under development and not yet recommended for production use.
+
+## What is Lean Builder?
+
+[Lean Builder](https://pub.dev/packages/lean_builder) is a streamlined Dart build system that offers:
+- Fast incremental builds (often under 1 second)
+- Parallel processing for maximum efficiency
+- Watch mode with hot reload support
+- Simple, declarative builder configuration
+
+## Current Implementation
+
+The infrastructure for lean_builder support has been added to retrofit_generator, but the full implementation is pending until:
+1. Lean Builder reaches a stable release (currently at v0.1.2)
+2. The retrofit_generator codebase is fully adapted to lean_builder's API
+
+## Using build_runner (Recommended)
+
+For now, please continue using build_runner for code generation:
+
+```bash
+# One-time build
+dart pub run build_runner build
+
+# Watch mode (recommended during development)
+dart pub run build_runner watch --delete-conflicting-outputs
+```
+
+## Future Usage (When Available)
+
+Once lean_builder support is fully implemented, you'll be able to use:
+
+```bash
+# One-time build
+dart run lean_builder build
+
+# Watch mode with hot reload
+dart run lean_builder watch --dev
+```
+
+## Configuration
+
+### pubspec.yaml
+
+When lean_builder support is ready, your `pubspec.yaml` will include:
+
+```yaml
+dependencies:
+  retrofit: ^4.6.0
+  dio: ^5.0.0
+  json_annotation: ^4.9.0
+
+dev_dependencies:
+  retrofit_generator: ^10.0.0
+  lean_builder: ^0.1.2  # or latest version
+  json_serializable: ^6.10.0
+```
+
+### build.yaml (Optional)
+
+You can keep your existing `build.yaml` configuration. Lean Builder will respect these settings when support is fully implemented:
+
+```yaml
+targets:
+  $default:
+    builders:
+      retrofit_generator:
+        options:
+          auto_cast_response: true
+```
+
+## Migration Path
+
+When lean_builder support becomes stable:
+
+1. **No code changes required** - Your @RestApi annotations and API definitions remain the same
+2. **Update dependencies** - Add lean_builder to dev_dependencies
+3. **Switch build command** - Use `dart run lean_builder build` instead of `build_runner`
+4. **Enjoy faster builds** - Experience significantly faster incremental builds
+
+## Contributing
+
+If you're interested in helping complete the lean_builder integration, please:
+1. Check the [retrofit.dart GitHub repository](https://github.com/trevorwang/retrofit.dart)
+2. Review the [lean_builder documentation](https://pub.dev/packages/lean_builder)
+3. Submit a pull request or open an issue with your ideas
+
+## Support
+
+For questions or issues:
+- **retrofit.dart**: https://github.com/trevorwang/retrofit.dart/issues
+- **lean_builder**: https://github.com/Milad-Akarie/lean_builder/issues
+
+## Timeline
+
+Follow the retrofit.dart repository for updates on when lean_builder support will be fully available. The maintainers are monitoring lean_builder's development and will complete the integration when appropriate.

generator/CHANGELOG.md

@@ -1,3 +1,11 @@
+## 10.0.8 (Unreleased)
+
+- Add experimental lean_builder support infrastructure
+- Add `lean_builder` as a dependency for future integration
+- Add `lib/lean_builder.dart` entry point for lean_builder users
+- Add comprehensive documentation for lean_builder support
+- Note: Full lean_builder implementation is pending until lean_builder reaches stability
+
 ## 10.0.6
 
 - Update `protobuf` to 5.0.0

generator/lib/lean_builder.dart

@@ -0,0 +1,48 @@
+/// Lean Builder entry point for Retrofit code generator.
+///
+/// **⚠️ Experimental Feature ⚠️**
+///
+/// This file provides experimental lean_builder support for retrofit_generator.
+/// Lean Builder support is currently under development and not yet recommended
+/// for production use.
+///
+/// ## Current Status
+///
+/// While the infrastructure for lean_builder support has been added, the
+/// retrofit_generator package is currently optimized for build_runner. Full
+/// lean_builder integration is planned for future releases once lean_builder
+/// reaches a stable version.
+///
+/// ## Usage (Experimental)
+///
+/// For those who want to try the experimental support:
+///
+/// 1. Add lean_builder to your dev_dependencies:
+/// ```yaml
+/// dev_dependencies:
+///   lean_builder: ^0.1.2
+///   retrofit_generator: <version>
+/// ```
+///
+/// 2. For now, please continue using build_runner:
+/// ```bash
+/// dart pub run build_runner build
+/// # or for watch mode:
+/// dart pub run build_runner watch
+/// ```
+///
+/// ## Future Plans
+///
+/// Once lean_builder reaches stability and this integration is complete, you'll
+/// be able to use:
+/// ```bash
+/// dart run lean_builder build
+/// # or for watch mode with hot reload:
+/// dart run lean_builder watch --dev
+/// ```
+///
+/// For updates on lean_builder support, visit:
+/// https://github.com/trevorwang/retrofit.dart
+library;
+
+export 'package:retrofit_generator/src/lean_generator.dart';

generator/lib/src/lean_generator.dart

@@ -0,0 +1,46 @@
+import 'dart:async';
+
+import 'package:lean_builder/builder.dart';
+import 'package:lean_builder/element.dart';
+import 'package:retrofit/retrofit.dart' as retrofit;
+
+/// Lean Builder generator for Retrofit.
+///
+/// This generator provides lean_builder support for retrofit_generator,
+/// allowing faster incremental builds with lean_builder.
+///
+/// Note: This is an experimental feature. For production use, we recommend
+/// using the traditional build_runner approach until lean_builder support
+/// is fully stable.
+///
+/// This generator is automatically discovered by lean_builder through the
+/// @LeanGenerator.shared() annotation, which marks it as a shared part builder
+/// (similar to build_runner's shared part builders).
+@LeanGenerator.shared()
+class RetrofitLeanGenerator extends GeneratorForAnnotatedClass<retrofit.RestApi> {
+  RetrofitLeanGenerator();
+
+  @override
+  FutureOr<String?> generateForClass(
+    BuildStep buildStep,
+    ClassElement classElement,
+    ElementAnnotation annotation,
+  ) async {
+    // The retrofit generator is currently optimized for build_runner/source_gen.
+    // Full lean_builder support requires adapting the codebase to use lean_builder's
+    // analyzer abstractions instead of source_gen's API.
+    //
+    // For now, this serves as a placeholder for future lean_builder support.
+    // Users should continue using build_runner for code generation:
+    //   dart pub run build_runner build
+
+    throw UnsupportedError(
+      'Lean Builder support for retrofit_generator is not yet fully implemented.\n'
+      'The retrofit_generator package currently works with build_runner.\n\n'
+      'To generate code, please use:\n'
+      '  dart pub run build_runner build\n\n'
+      'For more information, see: https://github.com/trevorwang/retrofit.dart\n\n'
+      'Lean Builder support is planned for a future release once lean_builder reaches stable.',
+    );
+  }
+}

generator/pubspec.yaml

@@ -19,6 +19,7 @@ dependencies:
   code_builder: ^4.10.1
   dart_style: ^3.1.1
   dio: ^5.8.0
+  lean_builder: ^0.1.2
   protobuf: ^5.0.0
   retrofit: ^4.7.3
   source_gen: '>=3.1.0 <5.0.0'