dart-use-ffigen

name	dart-use-ffigen
description	Guide agents to use `package:ffigen` to automatically generate FFI bindings instead of writing them manually. Use this skill when a task involves writing new FFI bindings, extending C/Objective-C/Swift integrations, or replacing hand-crafted `dart:ffi` setups in logd.

Generating FFI Bindings for logd

Principles

1. No Hand-Written FFI Bindings: Never write manual DynamicLibrary.lookup, @Native functions, or raw struct classes if headers exist.
2. Path Resolution: Resolve all paths relative to Platform.script in the generator script to ensure it is runnable from any package directory.
3. Location: Place the generator script at tool/ffigen.dart and output generated bindings to lib/src/third_party/ with a .g.dart extension.
4. Tree Shaking: Enable recorded usage on all functions by setting recordUse: (_) => true and configure recordUseMapping target in Output to support tree shaking.

Example Config

import 'dart:io';
import 'package:ffigen/ffigen.dart';

void main() {
  final packageRoot = Platform.script.resolve('../');
  final entryHeader = packageRoot.resolve('third_party/native_lib.h');
  final bindingsOutput = packageRoot.resolve('lib/src/third_party/native_bindings.g.dart');
  final treeShakeMapping = packageRoot.resolve('lib/src/third_party/native_bindings.record_use_mapping.g.dart');

  FfiGenerator(
    headers: Headers(entryPoints: [entryHeader]),
    functions: Functions(
      include: (decl) => {'my_native_function'}.contains(decl.originalName),
      recordUse: (_) => true,
    ),
    output: Output(
      dartFile: bindingsOutput,
      recordUseMapping: treeShakeMapping,
      format: true,
      preamble: '// AUTO-GENERATED FILE. DO NOT EDIT.\n',
    ),
  ).generate();
}