LSP code action to discard unused variable

[francishamel]

Hi 👋 I'm not sure if I'm using the right term but I think it could be useful to add a code action that appends _ to a label in a pattern match to ignore it. There's already a hint for this case but it would be neat to quickly fix the issue via a code action. I added a screenshot to illustrate what I mean.

[lpil]

Could be useful! So would it change prop1:, to prop1: _?

Is there a reason to limit it to labelled arguments? Seems like being able to ignore any unused variable assigning pattern would be useful.

[francishamel]

Yeah, that's what I had in mind! 😄

Is there a reason to limit it to labelled arguments?

Not at all, I just didn't think further than this specific case tbh but it indeed would make sense to allow this code action on any unused variable assigning pattern.

[lpil]

Makes sense! Let's do the more general one :)

[clr-cera]

Hi! I would like to try to solve this issue, but it would be my first contribution and I'm a little lost.

Is there documentation explaining the language server structure?
Should this code action be preferred?

[GearsDatapacks]

There isn't much documentation on the structure of the project unfortunately. I was working on some but it never got to a finished state.

You're welcome to try this issue out, but do note that it's not particularly beginner friendly and you may want to have a go at some other more straightforward issues beforehand. Feel free to still give it a shot though!

In order to fix this issue, you will need to do something like the following:

• Create a new function in code_action.rs for this code action. You probably want to take inspiration from the "remove unused imports" and "fix name" code actions, as this one will need to derive its behaviour from warnings emitted by the compiler.
• As to whether it should be preferred, I'm not exactly sure. I would lean on the side of yes; I generally like preferred code actions to be ones where there's really only a single solution to a certain error or warning. Go for preferred and we can always change it later.
• Once you have your function, you will need to call it from the code_actions function in engine.rs.
• After that, add tests to tests/action.rs to verify that the code action is working as intended.

Hopefully that helps, let us know if you have any more questions!