Update platform name to pyemscripten

[ryanking13]

• Changelog

[agriyakhetarpal]

Thanks, @ryanking13! One typo (suggestion inlined below).

Also, one question: do we estimate a use for this legacy environment variable? Should we rather wait a bit before merging/releasing, until formal approval of the PEP, so we don't pull these changes into cibuildwheel and other users right away? It will make my job a bit easier :)

[ryanking13]

do we estimate a use for this legacy environment variable?

I am not very sure, but there might be people using old Pyodide runtime and making their own distribution with custom wheels (maybe @pepijndevos or @juntyr?) I don't want them to block updating pyodide-build version because of this.

Should we rather wait a bit before merging/releasing, until formal approval of the PEP, so we don't pull these changes into cibuildwheel and other users right away? It will make my job a bit easier :)

Yeah, even after merging this, we can delay the release until PEP 783 gets accepted.

[agriyakhetarpal]

Sounds good to me!

[juntyr]

I still build my distribution in-tree inside the Pyodide Docker container using synchronised pyodide, pyodide-build, and pyodide-recipes repos. So I will likely only experience this change once the new platform name is adopted across all three repositories (and Pyodide v0.30 is released and I upgrade to that). Still, I appreciate having the environment variable (maybe for a release or two) since I sometimes pull in newer recipes that require newer versions of pyodide-build.

TLDR: sounds good to me!

[agriyakhetarpal]

Would something like this work?

Suggested change

	### Changed
	- Platform name for the Pyodide wheel is now `pyemscripten` instead of `pyodide`, following the PEP 783 standard.
	If you want to use the old platform name, you can set the `USE_LEGACY_PLATFORM` environment variable to `1`.
	[#319](https://github.com/pyodide/pyodide-build/pull/319)
	### Changed
	- Platform name for the Pyodide wheel is now `pyemscripten` instead of `pyodide`, following the PEP 783 standard.
	If you want to use the old platform name, you can set the `USE_LEGACY_PLATFORM` environment variable to `1`. This environment variable will be available until Pyodide v0.31, and will be removed in v0.32.
	[#319](https://github.com/pyodide/pyodide-build/pull/319)

[ryanking13]

Actually, the pyemscripten platform has almost nothing to do with pyodide runtime itself. It only affects how packages are installed, and Pyodide does not check the platform name at all. It is only the pyodide venv (pyodide-build) or micropip that checks the platform. So I think it is weird to say that it will be removed in future Pyodide versions.

[agriyakhetarpal]

Ah, interesting. Thanks for the clarification!

[agriyakhetarpal]

I was drafting a release just now, but I remembered that we merged this PR. Should we wait for a bit, @ryanking13, or this safe to release for usage downstream?

[ryanking13]

@agriyakhetarpal

Oh yeah. Hmm, I am +1 for just making a release. I don't think that the platform name will be changed again. If that happens, let's just yank that version and release a new version.

[agriyakhetarpal]

Done, I'll create a new release after merging a PR for #324. Thanks!