languages: Separate control flow keywords for JS/TS/TSX

[azeier]

Related to #9461, inspired by #39683

await and yield both seem somewhat debatable on whether they should be considered the be control flow keywords.

For now I went with:

• await: no – The control flow effect of await is at a level does not seem relevant for syntax highlighting.
• yield: yes – yield directly affects the output of a generator, and is also included for consistency with Rust (Highlight control flow in Rust/C/C++ #39683).

Happy to change these either direction.

---

Release Notes:

• Improved granularity of keyword highlighting for JS/TS/TSX: Themes can now specify keyword.control for control flow keywords like if, else, return, etc.

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[azeier]

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[azeier]

switch_default is now handled explicitly, to avoid highlighting export default.

[MrSubidubi]

Thanks for this!

Regarding yield/await: I think I am leaning against await and somewhat against yield, because both do not really change the control flow in a "classical" way like e.g. return would.

That said, Helix highlights both: https://github.com/helix-editor/helix/blob/97aee4950fd9a08a78415cd8992354ae5cf3aaf0/runtime/queries/rust/highlights.scm#L233-L234

but then, just because they do does not mean we have to.

Given that I merged the other PR as is, I think it is fine to go with this one as is as well and iterate on it as needed.

Hence, thank you for this PR, your added input, big thank you for the very well crafted release notes and - finally - congratulations to your first contribution! 🎉

[wesguirra]

Any theme supporting this as of now?

[azeier]

I suspect it will take a while for themes to pick up on changes like this, but you can override it in your settings.json:

  "experimental.theme_overrides": {
    "syntax": {
      "keyword.control": {
        "color": "#ffffff"
      }
    }
  },

[hisbvdis]

@azeier , hello.
I tried to make PR with some change to the TSX language highlighting, but my PR was rejected.
And I can't build Zed from repository according to the manual.

If you have a free time, maybe you could create another PR with adding ability to highligh JSX-components besides JSX tags?
My previouse PR: #37183