rustdoc output on nightly uses bold text in Safari

[jwodder]

Running cargo +nightly doc on a library crate and viewing the resulting documentation in Safari 17.2 on macOS Sonoma 14.2 results in all non-code text being bold, like so:

However, if cargo doc is run on the same crate using Rust stable 1.74.1, the resulting docs are formatted correctly:

When the built-on-nightly docs are opened in Firefox or Chrome, the text is not bold. Recently-built docs on docs.rs are not bold in Safari at all.

Inspecting the web elements shows that Safari considers the text to have a font-weight of 400 (normal), so I'm guessing the problem is down to the selection of the font. However, this is where my web styling skills end.

Stable Rust version:

rustc --version --verbose:

rustc 1.74.1 (a28077b28 2023-12-04)
binary: rustc
commit-hash: a28077b28a02b92985b3a3faecf92813155f1ea1
commit-date: 2023-12-04
host: x86_64-apple-darwin
release: 1.74.1
LLVM version: 17.0.4

Nightly Rust version:

rustc +nightly --version --verbose:

rustc 1.76.0-nightly (445177724 2023-12-16)
binary: rustc
commit-hash: 445177724ac2beebf4faa5a3ffacb2adbe7e7846
commit-date: 2023-12-16
host: x86_64-apple-darwin
release: 1.76.0-nightly
LLVM version: 17.0.6

Crate used to build docs shown above: https://github.com/jwodder/strtoint (though the problem happens with every library crate I build docs for)

[notriddle]

I've bisected it: 2023-11-07 is good, 2023-11-08 is bad.

It's probably #115904

[notriddle]

A few other notes about this bug:

• Both of the OP screenshots are demonstrating a bug. Everything being bold is just more severe. It's supposed to look like this.

  

  Notice how, in this screenshot, the header is bold. It's too thin in both of the OP screenshots. I suspect this is the same bug, because it goes away when I fetch through python -mhttp.server.

• Also, the bug does not show up when I try to reproduce with python -mhttp.server. I can only make it happen using file:// URLs.

In other words, this has got to be a Safari bug.

[notriddle]

Found the problem. This is just a new manifestation of #98769

[kadiwa4]

Fixed by #122410.

Issue #85444 is used to find a solution for the remaining case (if you have dev tools disabled, the styling doesn't work at all).