arizona_watcher_fs

fs-based file watcher for Arizona's dev-mode hot reload (inotify on Linux, FSEvents on macOS, the Windows API on Windows).

Arizona defines the watcher as a behaviour, arizona_watcher, and ships no implementation, so a production build never carries a file-system dependency. arizona_watcher_fs is the implementation you add for development.

Installation

Add it to a dev-only profile in your rebar.config, so a production release never pulls it (or fs) in:

{profiles, [
    {dev, [
        {deps, [arizona_watcher_fs]}
    ]}
]}.

It needs Arizona 0.4 or newer, the first release with the arizona_watcher behaviour. On Linux, fs needs inotifywait (the inotify-tools package).

Usage

Name it as the reloader's watcher in your dev config:

%% config/dev.config
[
    {arizona, [
        {reloader, #{
            enabled => true,
            watcher => arizona_watcher_fs,
            rules => [
                #{directory => "src", patterns => [".*\\.erl$"],
                  callback => fun arizona_reloader:reload_erl/1},
                #{directory => "priv/static", patterns => [".*\\.css$"],
                  callback => fun arizona_reloader:reload_css/1}
            ]
        }}
    ]}
].

and run rebar3 as dev shell --config config/dev.config. Arizona refuses to boot with rules but no watcher, or with a watcher that is not on the code path, and says which dependency or key is missing.

A path counts as changed on created, modified, deleted, or renamed -- the last being the atomic-rename save (write a temp file, rename() it over the target) that vim, sed -i, and most editors use. A directory rename and a file moved out of the watched directory are ignored. Patterns, debouncing, and the callback are Arizona's (arizona_reloader_rule), so they behave the same whatever watcher runs underneath.

Dev releases

fs is a dependency of this package but deliberately not in its applications: starting the fs application runs its default watcher on the whole working directory. rebar3 shell puts every dependency on the code path, so nothing more is needed there. A dev release only bundles applications something lists, so add both to the dev profile's relx release, loaded and not started:

{profiles, [
    {dev, [
        {deps, [arizona_watcher_fs]},
        {relx, [{release, {my_app, "0.1.0"}, [my_app, {arizona_watcher_fs, load}, {fs, load}]}]}
    ]}
]}.

🚧 Status

arizona_watcher_fs is in 0.x, like Arizona itself. The core is functional and covered by tests, but the API may change between minor versions. Pin an exact version in your deps if you need stability across upgrades.

Contributing

Contributions are welcome! Run rebar3 precommit before opening a pull request: it checks formatting, runs xref, hank, dialyzer, and the docs build, and runs the tests with a 100% coverage gate. The integration tests watch a real directory, so on Linux they need inotifywait.

License

arizona_watcher_fs is open-source under the Apache 2.0 License on GitHub.

See LICENSE.md for more information.