Is there support for detecting unused local variables?

[jmbeach]

Hello 👋 Is there support for detecting unused local variables? I sometimes rename a variable (manually) and then forget to rename it elsewhere and fish doesn't complain at all that the old variable doesn't exist of course.

Is there a way to get a warning when a variable is unused?

[ndonfris]

Hello 👋 Is there support for detecting unused local variables? I sometimes rename a variable (manually) and then forget to rename it elsewhere and fish doesn't complain at all that the old variable doesn't exist of course.

Is there a way to get a warning when a variable is unused?

👋 Yeah so the next published release will have this in it. Infact I'm mostly done with it already besides needing to clean up the code base since I tried out structuring some logic differently.

This branch has changes that should include getting unused local symbols in your 4004 diagnostics.

If you end up writting any fish shell scripts in the next few days, it'd be really helpful to get a little outside code review on this project.
Building from source should only take 1 to 2 mins: yarn install && yarn dev

I'm pretty certain the upstream branch I linked you works for most common variable && function definitions, but any bugs would be awesome to tackle without foot gunning myself. There are significant improvements to how all FishSymbols including variables, use more strict groupings of rules to ensure they don't match with a false positive. However, there needs to be some significant refactoring to keep the project maintainable if we're to merge this. If you want to check out refactoring the code for this feature, it is right here.

LMK if you run into any bugs or issues installing that version!

[ndonfris]

Glad the newer branch is working significantly better for you! And ya sorry my first message got cut off so it wasn't very clear 🤣.

A full snippet of the code I was mentioning for argparse appears to work for me. Heres what I'm testing:

# ~/.config/fish/functions/foo.fish
function foo
   argparse h/help -- $argv; or return
   #           ^- cursor here
   
   echo $_flag_help    # ref
   set -q _flag_help   # ref
end

function __bar
    foo --help              # ref
end

# ~/.config/fish/completions/foo.fish
complete -c foo -s h -l help # ref
### code actions can auto generate this too

---

if this doesn't work with variables defined outside the current file

Do you have an example for this? As long as you're in an autoloaded fish path, set -gx some_var should get references that don't clash with its scope (e.g., a different scope w/ set -l some_var will exclude those locations from getReferences() output).

[ndonfris]

Took a peek at references.ts. Wow, clearly a lot has gone into this!

Haha thanks! Unfortunately, references in fish are pretty ambiguous, so I'm still trying to find a less verbose way of comparing nodes to another file's locations. Think I made it a little easier to work with from my push earlier today

[jmbeach]

Do you have an example for this

Oh, nope haha. I was just saying that preemptively. Even better!

[ndonfris]

Unused local variables are now merged into master and available on release v1.0.10.

Shouldn't be very different from the branch you tested here (besides some slight improvements in narrowing weird edge-cases I could find). They'll be shown using the same diagnostic as unused functions, 4004.

Thanks for the help testing and the source examples 🙏