nixpkgs-suyu/doc/languages-frameworks/dart.section.md

# Dart {#sec-language-dart}

## Dart applications {#ssec-dart-applications}

The function `buildDartApplication` builds Dart applications managed with pub.

It fetches its Dart dependencies automatically through `pub2nix`, and (through a series of hooks) builds and installs the executables specified in the pubspec file. The hooks can be used in other derivations, if needed. The phases can also be overridden to do something different from installing binaries.

If you are packaging a Flutter desktop application, use [`buildFlutterApplication`](#ssec-dart-flutter) instead.

`pubspecLock` is the parsed pubspec.lock file. pub2nix uses this to download required packages.
This can be converted to JSON from YAML with something like `yq . pubspec.lock`, and then read by Nix.

If the package has Git package dependencies, the hashes must be provided in the `gitHashes` set. If a hash is missing, an error message prompting you to add it will be shown.

The `depsListFile` must always be provided when packaging in Nixpkgs. It will be generated and printed if the derivation is attempted to be built without one. Alternatively, `autoDepsList` may be set to `true` only when outside of Nixpkgs, as it relies on import-from-derivation.

The `dart` commands run can be overridden through `pubGetScript` and `dartCompileCommand`, you can also add flags using `dartCompileFlags` or `dartJitFlags`.

Dart supports multiple [outputs types](https://dart.dev/tools/dart-compile#types-of-output), you can choose between them using `dartOutputType` (defaults to `exe`). If you want to override the binaries path or the source path they come from, you can use `dartEntryPoints`. Outputs that require a runtime will automatically be wrapped with the relevant runtime (`dartaotruntime` for `aot-snapshot`, `dart run` for `jit-snapshot` and `kernel`, `node` for `js`), this can be overridden through `dartRuntimeCommand`.

```nix
{ lib, buildDartApplication, fetchFromGitHub }:

buildDartApplication rec {
  pname = "dart-sass";
  version = "1.62.1";

  src = fetchFromGitHub {
    owner = "sass";
    repo = pname;
    rev = version;
    hash = "sha256-U6enz8yJcc4Wf8m54eYIAnVg/jsGi247Wy8lp1r1wg4=";
  };

  pubspecLock = lib.importJSON ./pubspec.lock.json;
  depsListFile = ./deps.json;
}
```

### Running executables from dev_dependencies {#ssec-dart-applications-build-tools}

Many Dart applications require executables from the `dev_dependencies` section in `pubspec.yaml` to be run before building them.

This can be done in `preBuild`, in one of two ways:

1. Packaging the tool with `buildDartApplication`, adding it to Nixpkgs, and running it like any other application
2. Running the tool from the package cache

Of these methods, the first is recommended when using a tool that does not need
to be of a specific version.

For the second method, the `packageRun` function from the `dartConfigHook` can be used.
This is an alternative to `dart run` that does not rely on Pub.

e.g., for `build_runner`:

```bash
packageRun build_runner -- build
```

Do _not_ use `dart run <package_name>`, as this will attempt to download dependencies with Pub.

### Usage with nix-shell {#ssec-dart-applications-nix-shell}

As `buildDartApplication` provides dependencies instead of `pub get`, Dart needs to be explicitly told where to find them.

Run the following commands in the source directory to configure Dart appropriately.
Do not use `pub` after doing so; it will download the dependencies itself and overwrite these changes.

```bash
cp --no-preserve=all "$pubspecLockFilePath" pubspec.lock
mkdir -p .dart_tool && cp --no-preserve=all "$packageConfig" .dart_tool/package_config.json
```

## Flutter applications {#ssec-dart-flutter}

The function `buildFlutterApplication` builds Flutter applications.

See the [Dart documentation](#ssec-dart-applications) for more details on required files and arguments.

```nix
{  flutter, fetchFromGitHub }:

flutter.buildFlutterApplication {
  pname = "firmware-updater";
  version = "unstable-2023-04-30";

  src = fetchFromGitHub {
    owner = "canonical";
    repo = "firmware-updater";
    rev = "6e7dbdb64e344633ea62874b54ff3990bd3b8440";
    sha256 = "sha256-s5mwtr5MSPqLMN+k851+pFIFFPa0N1hqz97ys050tFA=";
    fetchSubmodules = true;
  };

  pubspecLock = lib.importJSON ./pubspec.lock.json;
  depsListFile = ./deps.json;
}

### Usage with nix-shell {#ssec-dart-flutter-nix-shell}

See the [Dart documentation](#ssec-dart-applications-nix-shell) nix-shell instructions.
```