`union` in source code isn't syntax-highlighted properly

[theemathas]

At https://docs.rs/crate/smallvec/1.15.1/source/src/lib.rs#622, union is not syntax-highlighted as a keyword in the source code page of docs.rs.

Note that the source code page that's generated by rustdoc at https://docs.rs/smallvec/1.15.1/src/smallvec/lib.rs.html#622 is highlighted properly

[syphar]

thank you for the report!

Yes, it's definitely a bug.

We're using server-side syntax highlighting for our own source views, I assume there is something outdated with the rust syntax file the library ships, or we ship in our codebase.

[Carbonhell]

I investigated this issue, and I believe the root cause is the Sublime Packages (https://github.com/rust-lang/docs.rs/tree/main/crates/bin/docs_rs_web/assets/syntaxes) not being updated since 2022 (except for a small change for Python, see commit history pre-crate refactor here).

Investigating the changes in the Rust files in the original repository, I noticed there are more issues with highlighting other than the union keyword, which can be seen in the following screenshots:
(current docs.rs):

with an updated Rust Sublime package:

1. precise capturing angle brackets are incorrectly highlighted;
2. loop labels are mistaken as lifetimes;
3. trait aliases break syntax highlighting.

There are most likely other issues as I only checked the most recent commits in the sublime repository, and the same may apply for the highlighting features of other languages (assuming they're used, as they're present in this repository). I think the easiest solution would be to do a sync of the whole assets/syntaxes folder - I will do some more tests in the next days and open up a PR for this

[syphar]

thanks for the all the research!

two things I wonder to prevent the maintaince issue in the future

• Doesn't syntect already include a set of syntax definitions? Is there a downside to using them?
• would something like two-face work? Would important syntaxes be missing then?

[syphar]

more contex:

• Replace client-side highlight.js by server-side syntect highlighting #1842 was the original PR
• it seems like the syntect-builtin definitions might be outdated: Support changes to sublime-syntax from Sublime Text Build 4075 trishume/syntect#323

[Carbonhell]

Sorry for the slow response - the issue about the syntect-builtin definitions being out of date also affects the two-face crate, as it relies on bat which is also stuck to a Packages submodule dated 6 years ago: https://github.com/sharkdp/bat/tree/master/assets/syntaxes. I think we might be able to still use the ones present in this repo, while only updating at least Rust and TOML, but that'd be more of a bandaid than a full solution and it wouldn't cover updates for languages that aren't supported by syntect.

I remembered reading about a recent project by fasterthanlime related to syntax highlighting: https://fasterthanli.me/articles/introducing-arborium which is actually related to this issue: #3040. I think that issue is specific to highlighting code in documentation blocks of a crate, rather than highlighting the source code of a crate (what we care about here). But I think arborium might be a potential alternative for this use case as well. What do you think?

[GuillaumeGomez]

Sadly no: it uses C libraries that need to be compiled and is very (too) big for such a simple syntax. The result is not worth the cost.