Triggering on type formatting on deletions

[vinistock]

Generally, on type formatting is used to autocomplete code as the developer types specific characters. However, there are also use cases for doing similar operations on deletions.

For example, when doing string interpolation in Ruby, we are currently closing brace automatically using on type formatting (from "#{" to "#{}"), but we'd also be interested in removing that closing brace in case the user deletes the opening one with backspace (from "#{}" to "#"). There are other use cases involving end tokens and pipes too.

Is it possible to trigger on type formatting on backspace? And if so, what's the trigger character?

[dbaeumer]

I think using on type formatting for this is not a good idea since it is not designed for this.

@aeschli I remember you have some comparable adjustments in HTML for tags. How do you do this there?

[aeschli]

Yes, we have a custom LSP request for adding quotes and for closing tags.
We generalized it by calling it autoInsertion. Given a trigger character the autoInsertion provider is asked for an edit.

We don't have something similar for deletions

[vinistock]

For HTML tags, you could do something similar with deletions. For example, if you have <p></p> and you completely remove the closing tag, the opening tag can be automatically removed (same for the other way around).

Is there interest in having this for language servers? In my head, it sounds like a part of on type formatting, but Dirk mentioned that's not adequate at the moment. Would it be a new request or a modification to on type formatting?

[dbaeumer]

If we add this is should be a new request.

[vinistock]

I did a quick attempt to implement this as a custom request, but I now realize the issue you mentioned. I tried hooking it up on DidChangeTextDocument, but for deletions the contentChanges are simply empty. We don't know which key press triggered it or what is the location of the edit.

Are there any alternatives way to implement this? Feels like it requires some changes in VS Code itself to support it.

[dbaeumer]

@aeschli any additional tips