# Mill Scale

An opinionated rust module for
[flakelight](https://github.com/nix-community/flakelight).

## Features

Included checks:

- Build project
- Build examples (if they exist)
- Verify MSRV (if specified in `Cargo.toml`)
- Test and clippy with default features
- Test and clippy with all features (if features are defined)
- Test and clippy with no default features (if default features are defined)

## Usage

```nix
{
  inputs = {
    nixpkgs.url = "nixpkgs/nixos-24.05";
    flakelight = {
      url = "github:nix-community/flakelight";
      inputs.nixpkgs.follows = "nixpkgs";
    };
    mill-scale = {
      url = "git+https://codeberg.org/icewind/mill-scale.git";
      inputs.flakelight.follows = "flakelight";
    };
  };
  outputs = { mill-scale, ... }: mill-scale ./. {};
}
```

## Dependencies

(Native) build dependencies can be specified with the following

```nix
{
  # ...
  outputs = { mill-scale, ... }: mill-scale ./. {
    nativeBuildInputs = pkgs: [pkgs.libfoo];
    buildInputs = pkgs: [pkgs.libbar];
  };
}
```

Additionally, dependencies for the following crates should be automatically
detected

- openssl
- udev
- dbus
- servo-fontconfig
- sodium
- x11-dl
- glutin_glx
- wayland
- libsodium
- freetype
- alsa
- wgpu

## Development tooling

Development tools for working with the following crates are automatically added
to the dev-shell when needed

- cargo-insta
- sqlx

## Usage with GitHub Actions

### Single runner

```yaml
name: "CI"
on:
  pull_request:
  push:

jobs:
  checks:
    runs-on: ubuntu-latest
    steps:
      - uses: actions/checkout@v4
      - uses: cachix/install-nix-action@v26
        # insert cache setup here
      - run: nix flake check --keep-going
```

### Split over multiple runners

This automatically creates one job per check, allowing them to run in parallel.

This might be slower than running them all in the same runner depending on the
time each check takes and the size of the intermediates that has to be
downloaded from the cache.

```yaml
name: "CI"
on:
  pull_request:
  push:

jobs:
  matrix:
    runs-on: ubuntu-latest
    outputs:
      matrix: ${{ steps.set-matrix.outputs.matrix }}
    steps:
      - uses: actions/checkout@v4
      - uses: cachix/install-nix-action@v27
      - id: set-matrix
        run:
          echo "matrix={\"check\":$(nix eval --json '.#checks.x86_64-linux'
          --apply 'builtins.attrNames')}" | tee -a $GITHUB_OUTPUT

  checks:
    runs-on: ubuntu-latest
    needs: [matrix]
    strategy:
      fail-fast: false
      matrix: ${{fromJson(needs.matrix.outputs.matrix)}}
    name: ${{ matrix.check }}
    steps:
      - uses: actions/checkout@v4
      - uses: cachix/install-nix-action@v26
        # insert cache setup here
      - run: nix build .#checks.x86_64-linux.${{ matrix.check }}
```

## Cross-compiling

Cross-compiling can be enabled with the following

```nix
{
  # ...
  outputs = { mill-scale, ... }: mill-scale ./. {
    crossTargets = [
      "x86_64-unknown-linux-musl"
      "x86_64-pc-windows-gnu"
    ];
  };
}
```

This adds cross-compiled package with the same name as the target to the
`packages`.

### Cross-compiling with GitHub Action

A `lib.crossMatrix` flake output is provided to help with setting up
cross-compiling in CI.

This contains a list of targets and the binary suffix (e.g. `.exe`) for each
target.

```yaml
on: [push, pull_request]

name: CI

jobs:
  matrix:
    runs-on: ubuntu-latest
    outputs:
      cross-matrix: ${{ steps.set-matrix.outputs.cross-matrix }}
    steps:
      - uses: actions/checkout@v4
      - uses: cachix/install-nix-action@v27
      - id: set-matrix
        run: |
          echo "cross-matrix={\"include\":$(nix eval --json '.#lib.crossMatrix')}" | tee -a $GITHUB_OUTPUT

  build:
    runs-on: ubuntu-latest
    needs: [matrix]
    strategy:
      fail-fast: false
      matrix: ${{fromJson(needs.matrix.outputs.cross-matrix)}}
    steps:
      - uses: actions/checkout@v4
      - uses: cachix/install-nix-action@v27
        # insert cache setup here
      - run: nix build .#${{ matrix.target }}
      - uses: actions/upload-artifact@v4
        with:
          name: crate-name-${{ matrix.target }}
          path: result/bin/crate-name${{ matrix.binary-suffix }}
```

## Credits

This flake is based on
[flakelight-rust](https://github.com/accelbread/flakelight-rust), credit for
most ideas got to accelbread.