nitrogen_cli 0.4.0

CLI for Nitrogen Modules. Scaffold new Flutter FFI plugins and generate native bridge code.

nitrogen_cli ⚡

CLI tool for Nitrogen plugins. Scaffold, generate, and link Nitrogen FFI plugins from the command line.

⚡ For Nitro docs visit: nitro.shreeman.dev

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Installation

# From this monorepo (local development):
dart pub global activate --source path packages/nitrogen_cli

# Or from pub.dev:
dart pub global activate nitrogen_cli

Add the Dart pub global bin to your PATH (one-time):

# ~/.zshrc or ~/.bashrc:
export PATH="$PATH:$HOME/.pub-cache/bin"

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Running nitrogen without arguments launches an interactive TUI dashboard. From there you can init, generate, link, doctor, and update with live visual feedback.

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Commands

nitrogen init

Scaffolds a complete Nitrogen plugin from scratch with pre-wired native configurations.

nitrogen init
# → prompts for plugin name, then generates everything

What it creates:

File	Description
lib/src/<name>.native.dart	Starter spec — define your API here
ios/Classes/<Name>Impl.swift	Starter Swift implementation
ios/Classes/Swift<Name>Plugin.swift	Flutter plugin registrar
ios/<name>.podspec	Pre-configured: Swift 5.9, iOS 13.0, C++17, HEADER_SEARCH_PATHS
ios/Package.swift	Swift Package Manager support
android/.../<Name>Impl.kt	Starter Kotlin implementation
android/.../<Name>Plugin.kt	Flutter plugin registrar
src/CMakeLists.txt	NDK build file
pubspec.yaml	Pre-wired with nitro and nitro_generator

You only ever edit: the spec, the Kotlin impl, and the Swift impl (or a single C++ impl). Everything else is generated.

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nitrogen generate

Runs flutter pub get + build_runner build and syncs all generated files to their native destinations.

nitrogen generate

What it produces (per .native.dart spec):

Output	Description
lib/src/*.g.dart	Dart FFI implementation
lib/src/generated/kotlin/*.bridge.g.kt	Kotlin JNI bridge (NativeImpl.kotlin)
lib/src/generated/swift/*.bridge.g.swift	Swift @_cdecl bridge (NativeImpl.swift)
lib/src/generated/cpp/*.bridge.g.h	C header (all modes)
lib/src/generated/cpp/*.bridge.g.cpp	C++ bridge (all modes)
lib/src/generated/cmake/*.CMakeLists.g.txt	CMake fragment (all modes)
lib/src/generated/cpp/*.native.g.h	Abstract C++ interface (NativeImpl.cpp)
lib/src/generated/cpp/test/*.mock.g.h	GoogleMock stub (NativeImpl.cpp)
lib/src/generated/cpp/test/*.test.g.cpp	Test starter (NativeImpl.cpp)

NativeImpl.cpp awareness: .bridge.g.swift files that contain only a "Not applicable" placeholder are never copied to ios/Classes/. Instead, the generated .native.g.h headers are synced there so Clang can resolve them during iOS builds.

After generation, nitrogen generate also runs pod install in any ios/ directory it finds.

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nitrogen link

Wires native build files (CMake, Podspec, Kotlin plugin, Swift plugin, .clangd) to the generated code.

nitrogen link

What it wires:

• Adds include(...) for each .CMakeLists.g.txt into src/CMakeLists.txt
• Adds System.loadLibrary("lib") to android/.../Plugin.kt
• Skips JniBridge.register(...) for all-cpp plugins
• Sets HEADER_SEARCH_PATHS + DEFINES_MODULE in the iOS .podspec (and macOS .podspec when macos/ exists)
• Injects bridge registration into ios/*Plugin.swift and macos/*Plugin.swift for Swift/Kotlin modules
• Skips Swift bridge registration step for all-cpp plugins
• Creates ios/Classes/dart_api_dl.c and macos/Classes/dart_api_dl.c forwarders if missing
• Copies nitro.h to both ios/Classes/ and macos/Classes/
• Updates .clangd to include generated/cpp/test/ for GoogleMock IDE support when cpp modules exist
• Strips redundant #include "*.bridge.g.cpp" directives from src/ files

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nitrogen doctor

Deep health check of every layer of your native build. Read-only — no files are changed.

nitrogen doctor

Sections checked:

Section	Key checks
System Toolchain	clang++, Xcode, Android NDK, Java
pubspec.yaml	nitro, build_runner, nitro_generator deps; iOS and macOS plugin platform config
Generated Files	Every expected output file — present, not stale
CMakeLists.txt	NITRO_NATIVE, dart_api_dl.c, add_library(lib) target
Android	kotlin-android, kotlinOptions, generated/kotlin sourceSets, System.loadLibrary, JniBridge.register
iOS	.podspec headers/C++17, Swift version, dart_api_dl.c, nitro.h, NITRO_EXPORT, .bridge.g.mm count
macOS	.podspec headers/C++17, Swift version, dart_api_dl.c, nitro.h, NITRO_EXPORT, .bridge.g.mm count, Swift plugin registration
NativeImpl.cpp (cpp modules only)	${lib}_register_impl wired up, .clangd includes test dir

NativeImpl.cpp awareness:

• Android: when all specs use NativeImpl.cpp, Kotlin JNI bridge checks are shown as ℹ info (not required) instead of errors.
• iOS: Registry.register check skipped; checks for .native.g.h headers in ios/Classes/ instead; no .bridge.g.mm warning.
• Generated files: .bridge.g.kt / .bridge.g.swift shown as ℹ info (placeholder) for cpp modules; .native.g.h, .mock.g.h, .test.g.cpp checked as required outputs.

Exit codes: 0 = all checks pass, 1 = one or more errors (suitable for CI).

# .github/workflows/build.yml
- name: Nitrogen health check
  run: |
    dart pub global activate nitrogen_cli
    nitrogen doctor

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Platform Targeting

Each platform is configured independently via the @NitroModule annotation. All three platforms can be mixed and matched:

// iOS + Android Swift/Kotlin, macOS via direct C++
@NitroModule(lib: 'sensor', ios: NativeImpl.swift, android: NativeImpl.kotlin, macos: NativeImpl.cpp)
abstract class SensorModule extends HybridObject { ... }

// All three platforms using direct C++ (same implementation everywhere)
@NitroModule(lib: 'math', ios: NativeImpl.cpp, android: NativeImpl.cpp, macos: NativeImpl.cpp)
abstract class Math extends HybridObject { ... }

// iOS + macOS Swift, Android Kotlin
@NitroModule(lib: 'plugin', ios: NativeImpl.swift, android: NativeImpl.kotlin, macos: NativeImpl.swift)
abstract class MyPlugin extends HybridObject { ... }

Note: macos: NativeImpl.kotlin is not valid — Kotlin is not a native macOS language. The generator will emit an INVALID_MACOS_IMPL error at build time.

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NativeImpl.cpp Workflow

For plugins where both platforms use direct C++:

// lib/src/math.native.dart
@NitroModule(lib: 'math', ios: NativeImpl.cpp, android: NativeImpl.cpp, macos: NativeImpl.cpp)
abstract class Math extends HybridObject {
  static final Math instance = _MathImpl();
  double add(double a, double b);
}

nitrogen generate   # → math.native.g.h (abstract C++ interface)
nitrogen link       # → wires CMake, podspec, .clangd

// src/HybridMath.cpp  (you write this)
#include "math.native.g.h"

class HybridMathImpl : public HybridMath {
public:
    double add(double a, double b) override { return a + b; }
};

static HybridMathImpl g_math;

// Auto-register on shared library load — no manual init call needed.
// (Generated by nitrogen link via linkCppImplStubs)
__attribute__((constructor))
static void math_auto_register() {
    math_register_impl(&g_math);
}

nitrogen doctor     # → checks register_impl is wired, headers synced, .clangd up to date

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Spec Example (Swift/Kotlin path)

// lib/src/sensor.native.dart
import 'package:nitro/nitro.dart';
part 'sensor.g.dart';

@HybridEnum(startValue: 0)
enum DeviceStatus { idle, busy, error }

@HybridStruct(packed: true)
class SensorData {
  final double temperature;
  final double humidity;
  const SensorData({required this.temperature, required this.humidity});
}

@NitroModule(lib: 'sensor', ios: NativeImpl.swift, android: NativeImpl.kotlin, macos: NativeImpl.swift)
abstract class SensorModule extends HybridObject {
  static final SensorModule instance = _SensorModuleImpl();

  DeviceStatus getStatus();
  void updateSensors(SensorData data);

  @NitroStream(backpressure: Backpressure.dropLatest)
  Stream<SensorData> get sensorStream;
}

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Requirements

Tool	Minimum
Dart SDK	3.3.0+
Flutter SDK	3.22.0+
Android NDK	26.1+
Kotlin	1.9.0+
iOS Deployment Target	13.0+
Xcode	15.0+

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Related

• nitro — Runtime (base classes, annotations, helpers)
• nitro_generator — build_runner code generator
• Getting started guide — step-by-step walkthrough