Add JS/TS code folding support to language server

[camerondubas]

Part of #626

This adds support for code folding in js & ts files. This implementation is based on tsserver's. This does not add support for gts/gjs files.

Folding seems to work as expected, but two odd things had to be handled:

• The OutliningSpans have TextSpans with inclusive length, leading to off-by-one errors. I handled this inline, but I'm concerned that this is unintentional and may not always be the case.
• There are some additional OutliningSpans that incorrectly have a "0" starting offset and don't match any foldable code. I believe these are retrieved from the template file and are meant to represent their folding ranges. As is, these are superfluous and cause an incorrect FoldingRange on line 1 of every component file.

Any guidance on better ways to handle either of these would be appreciated!

Recording.2023-10-14.233242.mp4

[NullVoxPopuli]

I really appreciate you adding all these tests in your PRs <3

[NullVoxPopuli]

is this excluding the last }? I count that it should be 7?

[camerondubas]

The last line is excluded if it's just a closing bracket (https://github.com/typed-ember/glint/pull/632/files#diff-cadffc59ac4fd3c9fd1cd7488980fc9cfea40cd5a93129f1021c54c810980e20R503). This is so that folded functions keep the } visible:

// Like this when folded
function topLevel() {
}

// instead of this
function topLevel() {

this is consistent with the TS language server's folding.

[dfreeman]

Thank you @camerondubas!

I just wanted to say this hasn't been forgotten about; you've asked some good questions about the implementation that I'm expecting will take a little time to investigate, and I haven't had a lot of uninterrupted time this week. I'm aiming to give a more thorough look early next week, but please ping me if you don't hear anything—I want to make sure this doesn't sit idle too long!

[camerondubas]

@dfreeman I updated this with the latest main. Friendly bump to take a look at this when you have some time. No rush though, life's busy! Cheers

[lifeart]

Here is template part if needed: https://github.com/lifeart/ember-language-server/blob/component-context-info-origin/src/folding-provider/template-folding-provider.ts, quite easy to implement.

[NullVoxPopuli]

@camerondubas any chance you want to rebase? <3

[NullVoxPopuli]

looks like a floating dep dropped node 16, breaking our ci.

I'd consider this non-blocking for merge, myself, and fixing the floating dep issue can happen in a different PR