cargo-watch/TROUBLESHOOT.md

Cargo Watch Troubleshooting

In all cases, start by checking your version with cargo watch --version and, if necessary, upgrading to the latest one.

RLS is slow while using cargo watch, or vice versa, or it's waiting for the project lock a lot

Cargo builds (and checks, and clippy, and tests because the tests have to be built) take out a lock on the project so two cargo instances don't run at the same time.

However, Rust Analyzer is much better at this, so use that instead of RLS.

I'm getting errors on Windows 7 (or lower)

Cargo Watch versions 5.0.0 and up (and Watchexec versions 1.3.0 and up) do not support Windows 7 or lower. Support will not be added. Issues for Windows <=7 will be closed. If it works, lucky you, but that is not intentional.

I want to run cargo-watch directly, without going through cargo

You can! But you'll have to specify the watch subcommand as the first argument, like so:

$ cargo-watch watch -x build

I want to run cargo-watch outside of a Cargo project

That's not supported. If you have a good reason to use a Cargo-specific tool outside a Cargo project, please open an issue! Otherwise, you'll probably be best served with using Watchexec.

If file updates seems to never trigger

Try using --poll to force the polling fallback.

If that still doesn't work, and you're using an editor that does "safe saving", like IntelliJ / PyCharm, you may have to disable "safe saving" as that may prevent file notifications from being generated properly.

Also try using the --why option to see if the paths you expect are changing.

Linux: If it fails to watch some deep directories but not others / "No space left on device"

You may have hit the inotify watch limit. Here's a summary of what this means and how to increase it.

If you want to only recompile one Cargo workspace member crate

Watching one or more specific workspace member is not natively supported yet, although you can use -w folder to approximate it.

Watching the entire workspace and running a command in one member is done via the usual -p option on the child command:

$ cargo watch -x 'build -p subcrate'

If it runs repeatedly without touching anything

That can happen when watching files that are modified by the command you're running.

If you're only running compiles or checks (i.e. any command that only affects the target/ folder) and you're using -w, you might be confusing the target-folder-ignorer. Check your options and paths.

You can also use the --watch-when-idle flag to ignore any event that happens while the command is running. This will become the default in 8.0.

If it runs repeatedly only touching ignored files

Make sure the files you ignored are the only ones being touched. Use the --why option to see exactly which files were modified and triggered the restart. Some programs and libraries create temporary files that may not match a simple ignore pattern.

As above, you can also use the --watch-when-idle flag to help.

I don't have colour in my cargo output / for cargo test

This sometimes happens on some terminal configurations or for test harnesses. A quick workaround (instead of going down the rabbit hole of debugging your console settings) is to pass --color=always to the command. E.g.

$ cargo watch -x 'check --color=always'

For test (and bench) commands, you'll need to pass the flag to the underlying program instead of cargo:

$ cargo watch -x 'test -- --color=always'

I want to compile my build with additional features

$ cargo watch --features foo,bar

will run cargo check --features foo,bar on every watched change.

The --features will be passed to every supported cargo subcommand.

$ cargo watch --features foo,bar -x build -x doc

will run both build and doc with the foo and bar features.

Something not covered above / I have a feature request

Please open an issue, or look through the existing ones. You may also want to look through issues for the Notify library this tool depends on, or the issues for the Watchexec tool that we use under the covers (where I am also a maintainer).

If you want more verbose output, try running with the --debug flag. Note that this will also enable debug mode for watchexec. When filing an issue, make sure to include a log with --debug enabled so problems can be diagnosed.

If your issue is a watchexec issue, open it there directly. If you're not sure, feel free to open it here, but if it is a watchexec issue, it will get closed in favour of the upstream issue.