nushell/devdocs/FAQ.md

Frequently asked question for developers

Let's collect some questions a lot of Nushell contributors have.

• How do I do....?
• Why do I need to do certain things a certain way?

Let's keep the answers concise and up to date (or general enough) to remain relevant

How do I properly test my feature or bugfix?

TODO (Probably fork out into its own file)

I want to report an error to the user

Approximate flow:

1. Are you reporting the error in the parser/static checking phase?
   • Use nu_protocol::ParseError variants
   • Follow the logic used in the context as we need to collect multiple errors for a good IDE experience
2. Pick the right nu_protocol::ShellError variant
   • Does a matching existing variant fit your need? (go to references of the ShellError variant for inspiration)
   • Check what context the miette macros add during formatting! (go to definition of ShellError)
   • If it is a one-of specific error, consider using a generic variant
   • Else add a new class of errors
     • add the necessary Span information
     • general shared error text, to inform and point to a resolution
     • dynamic information gathered from the error site
     • Don't use a tuple enum variant, named structs going forward only!
3. Are you in a command?
   • return Err(ShellError::...) and you're done in a Command::run
4. Do you want to report a warning but not stop execution?
   • NEVER println!, we can write to stderr if necessary but...
   • good practice: nu_protocol::cli_error::report_error or report_error_new
     • depending on whether you have access to a StateWorkingSet
   • if only relevant to in the field debugging: log-crate macros.

How do I check an environment variable?

TODO

WTF is PipelineMetadata?

TODO