stylo@0.5.0 requires `markupsafe` without providing or documenting it

[delan]

stylo@0.5.0 upgrades mako from 1.1.2 to 1.3.10, which made markupsafe mandatory. Unless the user provides a Python with markupsafe installed, stylo will not build.

Ubuntu images with cloud-init, like our ubuntu2204 image (and probably GitHub’s Ubuntu image), ship with markupsafe. Other platforms, including the macos13 and windows10 images used in Servo, don’t tend to ship with markupsafe, so this also breaks libservo builds without mach (servo/servo#37939).

$ cargo +1.85.0 new foo
$ cd foo
$ cargo +1.85.0 add stylo@0.5.0
$ cargo +1.85.0 build
   Compiling stylo v0.5.0
error: failed to run custom build command for `stylo v0.5.0`
[...]
  Traceback (most recent call last):
    File "/home/delan/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stylo-0.5.0/properties/build.py", line 14, in <module>
      from mako import exceptions
    File "/home/delan/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stylo-0.5.0/properties/mako-1.3.10-py3-none-any.whl/mako/exceptions.py", line 292, in <module>
    File "/home/delan/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stylo-0.5.0/properties/mako-1.3.10-py3-none-any.whl/mako/exceptions.py", line 289, in _install_highlighting
    File "/home/delan/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stylo-0.5.0/properties/mako-1.3.10-py3-none-any.whl/mako/exceptions.py", line 277, in _install_fallback
    File "/home/delan/.cargo/registry/src/index.crates.io-1949cf8c6b5b557f/stylo-0.5.0/properties/mako-1.3.10-py3-none-any.whl/mako/filters.py", line 14, in <module>
  ModuleNotFoundError: No module named 'markupsafe'

[delan]

See also @mrobinson’s comment, which may complicate fixing this:

I think the issue here is just that the mako wheel depends on pygments and markupsafe but they aren't included in the repository. Making things even more complicated it seems that markupsafe is completely platform-dependent C++ code so all of the downloadable wheel contain binaries.

[jschwe]

Can we get away with just documenting the requirement and recommending to setup the environment via uv before running cargo?

[delan]

i guess the best answer for this may depend on ecosystem expectations. @nicoburns?

[nicoburns]

I'd definitely prefer a solution that doesn't require users of the stylo crate to install anything if possible. People generally expect "cargo build" to just work.

Long-term I'd like to eliminate the python dependency entirely (either porting the python code to Rust, or running the codegen "offline" (prior to uploading to crates.io)) because Windows users dont tend to have Python pre-installed

[nicoburns]

#215 Reproduces this issue in Stylo CI

[delan]

that makes sense. in the meantime, is stylo’s dependency on python documented anywhere? how do consumers currently learn that they need python, and can we standardise this around uv like we’ve done in servo? requiring uv eliminates any confusion around what python version to use, and lets us install markupsafe without shipping dozens of wheels.

[nicoburns]

in the meantime, is stylo’s dependency on python documented anywhere?

I don't think so. It's definitely should be. Especially as the mako bump also means we require specifically Python 3.

how do consumers currently learn that they need python

Usually when their build fails I think.

without shipping dozens of wheels.

Markupsafe seems to have a pure-python fallback implementation. So perhaps we could just create one wheel with that implementation?

[Loirooriol]

For now I guess we can try reverting a3ef6a2 and f041478