Custom exit code

[tertsdiepraam]

Please complete the following tasks

• I have searched the discussions
• I have searched the open and rejected issues

Clap Version

3.0.10

Describe your use case

At the uutils project, we need to match the exit code of the original GNU utilities. GNU often (but not always) uses 1 as an exit code when the arguments are wrong, so we regressed when moving to clap 3 due to #1327 and #1653.

The relevant issue on our repository is uutils/coreutils#3102.

Describe the solution you'd like

I don't think there is a one size fits all solution for exit codes. Therefore, I'd like App to have some method that specifies the exit code in case of a usage error. The default would continue to be 2. It could look something like this:

App::new("test")
    .fail_exit_code(1);

I'm not sure what the best name would be. It could also be exit_code, usage_error_code or error_code.

Alternatives, if applicable

We also have our own error type with exit code information, which we could convert a clap error into. In this case we would implement conversion to our own error type and then use try_get_matches to get the error. However, this would require quite a bit of code for the conversion.

A third possible solution would be to provide a method on Error to modify the exit code before calling Error::exit(), which could be used like this:

App::new("test")
    .try_get_matches()
    .map_err(|e| e.exit_code(1).exit())

However, this solution is unintuitive for DisplayHelp and DisplayVersion, which should probably ignore this method.

Additional Context

I would be happy to try to implement this if this is indeed something you'd like to include. We're still very happy with clap! Thank you for this amazing crate!

[epage]

As part of our effort to trim down clap, we're focusing on the built-in / easy path being for the majority case while offering building blocks for the exceptions. I think exit codes fall in that boat. Here is an example of a program that provides custom exit codes: https://github.com/crate-ci/typos/blob/master/src/bin/typos-cli/main.rs#L17

I'd recommend using a testing tool like trycmd which will help in testing exit codes.

[tertsdiepraam]

I completely understand. Thank you for your time!

[OddBloke]

For anyone else who's wound up here, that example code has moved to: https://github.com/crate-ci/typos/blob/master/crates/typos-cli/src/bin/typos-cli/main.rs