watchexec/crates/lib/README.md

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# Watchexec library

_The library which powers [Watchexec CLI](https://watchexec.github.io) and other tools._

- **[API documentation][docs]**.
- Licensed under [Apache 2.0][license].
- Status: maintained.

[docs]: https://docs.rs/watchexec
[license]: ../../LICENSE


## Quick start

```rust ,no_run
use miette::{IntoDiagnostic, Result};
use watchexec::{
    Watchexec,
    action::{Action, Outcome},
    config::{InitConfig, RuntimeConfig},
    handler::{Handler as _, PrintDebug},
};

#[tokio::main]
async fn main() -> Result<()> {
    let mut init = InitConfig::default();
    init.on_error(PrintDebug(std::io::stderr()));

    let mut runtime = RuntimeConfig::default();
    runtime.pathset(["watchexec.conf"]);

    let conf = YourConfigFormat::load_from_file("watchexec.conf").await.into_diagnostic()?;
    conf.apply(&mut runtime);

    let we = Watchexec::new(init, runtime.clone())?;
    let w = we.clone();

    let c = runtime.clone();
    runtime.on_action(move |action: Action| {
        let mut c = c.clone();
        let w = w.clone();
        async move {
            for event in action.events.iter() {
                if event.paths().any(|(p, _)| p.ends_with("/watchexec.conf")) {
                    let conf = YourConfigFormat::load_from_file("watchexec.conf").await?;

                    conf.apply(&mut c);
                    let _ = w.reconfigure(c.clone());
                    // tada! self-reconfiguring watchexec on config file change!

                    break;
                }
            }

            action.outcome(Outcome::if_running(
                Outcome::DoNothing,
                Outcome::both(Outcome::Clear, Outcome::Start),
            ));

            Ok(())

            // (not normally required! ignore this when implementing)
            as std::result::Result<_, MietteStub>
        }
    });

    we.reconfigure(runtime);
    we.main().await.into_diagnostic()?;
    Ok(())
}

// ignore this! it's stuff to make the above code get checked by cargo doc tests!
struct YourConfigFormat; impl YourConfigFormat { async fn load_from_file(_: &str) -> std::result::Result<Self, MietteStub> { Ok(Self) } fn apply(&self, _: &mut RuntimeConfig) {} } use miette::Diagnostic; use thiserror::Error; #[derive(Debug, Error, Diagnostic)] #[error("stub")] struct MietteStub;
```


## Kitchen sink

The library also exposes a number of components which are available to make your own tool, or to
make anything else you may want:

- **[Command handling](https://docs.rs/watchexec/2/watchexec/command/index.html)**, to
  build a command with an arbitrary shell, deal with grouped and ungrouped processes the same way,
  and supervise a process while also listening for & acting on interventions such as sending signals.

- **Event sources**: [Filesystem](https://docs.rs/watchexec/2/watchexec/fs/index.html),
  [Signals](https://docs.rs/watchexec/2/watchexec/signal/index.html),
  [Keyboard](https://docs.rs/watchexec/2/watchexec/keyboard/index.html),
  (more to come).

- Finding **[a common prefix](https://docs.rs/watchexec/2/watchexec/paths/fn.common_prefix.html)**
  of a set of paths.

- And [more][docs]!

Filterers are split into their own crates, so they can be evolved independently:

- The **[Globset](https://docs.rs/watchexec-filterer-globset) filterer** implements the default
  Watchexec filter, and mimics the pre-1.18 behaviour as much as possible.

- The **[Tagged](https://docs.rs/watchexec-filterer-tagged) filterer** is an experiment in creating
  a more powerful filtering solution, which can operate on every part of events, not just their
  paths.

- The **[Ignore](https://docs.rs/watchexec-filterer-ignore) filterer** implements ignore-file
  semantics, and especially supports _trees_ of ignore files. It is used as a subfilterer in both
  of the main filterers above.

There are also separate, standalone crates used to build Watchexec which you can tap into:

- **[ClearScreen](https://docs.rs/clearscreen)** makes clearing the terminal screen in a
  cross-platform way easy by default, and provides advanced options to fit your usecase.

- **[Command Group](https://docs.rs/command-group)** augments the std and tokio `Command` with
  support for process groups, portable between Unix and Windows.

- **[Event types](https://docs.rs/watchexec-events)** contains the event types used by Watchexec,
  including the JSON format used for passing event data to child processes.

- **[Signal types](https://docs.rs/watchexec-signals)** contains the signal types used by Watchexec.

- **[Ignore files](https://docs.rs/ignore-files)** finds, parses, and interprets ignore files.

- **[Project Origins](https://docs.rs/project-origins)** finds the origin (or root) path of a
  project, and what kind of project it is.

## Rust version (MSRV)

Due to the unpredictability of dependencies changing their MSRV, this library no longer tries to
keep to a minimum supported Rust version behind stable. Instead, it is assumed that developers use
the latest stable at all times.

Applications that wish to support lower-than-stable Rust (such as the Watchexec CLI does) should:
- use a lock file
- recommend the use of `--locked` when installing from source
- provide pre-built binaries (and [Binstall](https://github.com/cargo-bins/cargo-binstall) support) for non-distro users
- avoid using newer features until some time has passed, to let distro users catch up
- consider recommending that distro-Rust users switch to distro `rustup` where available