Implement Termination for error_stack::Report

[gluax]

🌟 What is the purpose of this PR?

This adds custom error code support for error-stack

🔗 Related links

Closed #670.

Though the implementation has changed since I wrote the issue and learned more about the code base.

🔍 What does this change?

• Adds a method attach_exit_code(mut self, exit_code: u8) -> Self on the Report<C> struct.
• Adds a new field exit_code: Option<u8> on the ReportImpl struct.
• Implements the Termination trait for the Report<C> struct.

📜 Does this require a change to the docs?

The docs have been added.

🐾 Next steps

Please let me know if there are any changes that should be made.

🛡 What tests cover this?

There is the test doc test that passes. Let me know if I should add a separate test.

❓ How to test this?

1. Pull the forked repo.
2. Check out the feature/custom-exit-code branch.
3. Run cargo test --doc

📹 Demo

[CLAassistant]

All committers have signed the CLA.

[TimDiekmann]

Hi @gluax and thank you very much for the contribution!

I really like the idea of implementing Termination on Report. However, I think the API can be simplified (see comments). This sadly requires a nightly compiler to really use ExitCode, but as soon as the Provider API is stabilized, this would also be available on stable.

[vilkinsons]

@gluax This is awesome, thanks for contributing!

[TimDiekmann]

Thanks for applying the suggestions!

Would be great if you could add a small test checking for the right exit code. We don't have a tests module in report.rs yet, you may add one at the bottom of the file. 👍🏻

[gluax]

Example and test added! As well as the other suggested changes.

[TimDiekmann]

Only a few suggestions that you should be able to apply directly from GitHub, otherwise it seems to be ready for merging.

In order to merge, the Rust jobs and the CI-linting job has to pass, others can be ignored (they fail because of insufficient permissions, nothing you should need to worry about).

[TimDiekmann]

Thank you very much for your contribution, I really appreciate it! 🎉