Add compatibility for Pyodide-tagged wheels

[hoodmane]

We are changing our wheel platform tag to pyodide_2024_0 so we need to teach packaging to map Emscripten platform to this.

cc @henryiii

[hoodmane]

@mayeut @henryiii @pradyunsg would appreciate review on this from any of you (and running the workflow).

[hoodmane]

Tests and coverage check now pass locally for me.

[agriyakhetarpal]

I stumbled into this PR, somehow – I guess the tests are valid for only Python 3.12 and should be skipped for other Python versions, @hoodmane?

[agriyakhetarpal]

Now, we also pre-emptively need 2025_0 as we broke/will be breaking the ABI.

[juntyr]

+1 - it would be great if packaging installed from PyPi would just work out of the box in Pyodide

[agriyakhetarpal]

I guess the only remaining parts here are to generalise the ABI tags, so that emscripten_x_y_zw and pyodide_abcd_e, where $$x, y, z, w, a, b, c, d, e ∈ [0, 9] $$ work, and skip the tests on unsupported Python versions (by probably grabbing the Python version from pyodide config get python_version)?

[jezdez]

Should this really yield the generic platform here as well, or is an else missing, so that _generic_platforms is yielded similar to the fallback in platform_tags?

Suggested change

	if pyodide_abi_version:
	yield f"pyodide_{pyodide_abi_version}_wasm32"
	yield from _generic_platforms()
	if pyodide_abi_version:
	yield f"pyodide_{pyodide_abi_version}_wasm32"
	else:
	yield from _generic_platforms()

[henryiii]

I believe this is correct as is, since you want to also be able to match emscripten_... tags. pyodide is just a more specific tag.

[agriyakhetarpal]

If I've understood @hoodmane's recent work correctly, all our forthcoming tags will be labelled with pyodide_YYYY_N as per the Pyodide ABI information at https://pyodide.org/en/stable/development/abi.html#pyodide-2025-0-under-development and with PEP 783: https://peps.python.org/pep-0783/#specification that packaging will implement through this PR. I think the distinction is important, as emscripten is no longer the same as pyodide since 2025_0. In 2024, one could have both 2024_0 and emscripten_3_1_58, which meant the same thing. 2025_0 does not have an emcripten_4_0_9 equivalent.

[hoodmane]

I think we should keep it as is because emscripten_4_0_9 is the name of the platform and so it's the default tag. If anyone has wheels with this platform it makes sense to accept them.

[agriyakhetarpal]

Yes, okay to keep it if you say so! :)

[ofek]

What are the next steps for this?

[hoodmane]

This can only be merged once PEP 783 is approved.

[ofek]

Indeed, and what's the status of that? I haven't seen any discussion update in months so I don't quite understand the state of the proposal.

[hoodmane]

Well I assume you also asked on the discuss thread? You can see the new comments there.
https://discuss.python.org/t/pep-783-emscripten-packaging/86862/64

[ofek]

Ah I don't have notifications for that enabled apparently, thanks a lot!