[bazel][robotpy] Generate Python type stubs

[virtuald]

No description provided.

[auscompgeek]

Wouldn't this be equivalent, and much simpler?

Suggested change

	"//shared/bazel/rules/robotpy:host_platform": values,
	"@platforms//host": values,

[auscompgeek]

Hmm. I suspect we actually want this stuff to be effective when exec == target, rather than host == target. When host != exec this would still break.

[virtuald]

I told the 🤖 to only build artifacts once, and this is the design it proposed to implement. I don't have any idea if it actually did this:

Recommended design

1. Load Bazel’s generated HOST_CONSTRAINTS from @platforms//host:constraints.bzl.
2. Define a host-matching config_setting.
3. Keep extension modules and the stubgen runner in the target configuration.
4. Include .pyi targets in libraries and wheels only through a host-platform select():
   • Target matches host: generate/package stubs; extension compiles once.
   • Target differs from host: omit stub generation and .pyi files; wheel continues
     building.
5. Mark direct *.make_pyi targets host-compatible only, so explicitly requesting one
   during a cross-build reports it as incompatible rather than failing while importing
   the foreign extension.

[virtuald]

TODO: also add semiwrap update-init