Option to avoid download python exe from https://github.com/indygreg/python-build-standalone

[da-liii]

For example, in Github Action, we'd prefer to install the python needed by Pants itself by actions/setup-python.

[jsirois]

@darcy-shen that's a no-go. The whole point of scie-pants is that it ships with a Python interpreter you, as the consumer, are unaware of. It is absolutely not intended to work with an external interpreter. Do you actually care about the interpreter it uses, or just that it doesn't download the interpreter dynamically? If its the latter, that can be accomodated. Right now we just ship a "thin" scie that does not include the Python interpreter - to save space - but downloads it as needed instead. We can also ship "fat" scies that include the interpreter. That said, downloads will still happen (of wheels) when a new Pants version is installed.

I guess what I really need here is more explanation of why you want to avoid https://github.com/indygreg/python-build-standalone - due to the technology, due to the runtime use of the network, or some other reason?

[da-liii]

due to the technology

I have found a better way to install Python, see pantsbuild/pants#17962

due to the runtime use of the network

Yes, it can be unstable for me. The network is not guaranteed to be stable.

[da-liii]

We can also ship "fat" scies that include the interpreter.

That's a great idea.

[jsirois]

With scie-pants now converted to science for building its scie, creating fat scies for release is as easy as adding --invert-lazy cpython39 --app-name scie-pants-fat to the science command here:

scie-pants/package/src/scie_pants.rs

Lines 37 to 61 in 14ed784

	execute(
	Command::new(&skinny_scie_tools.science)
	.args([
	"lift",
	"--include-provenance",
	"--file",
	&format!(
	"scie-pants.bin={scie_pants_exe}",
	scie_pants_exe = path_as_str(scie_pants_exe)?
	),
	"--file",
	&format!(
	"tools.pex={tools_pex}",
	tools_pex = path_as_str(tools_pex_file)?
	),
	"build",
	"--dest-dir",
	path_as_str(&scie_pants_package_dir)?,
	"--use-platform-suffix",
	"--hash",
	"sha256",
	path_as_str(&scie_pants_manifest)?,
	])
	.current_dir(&build_context.workspace_root),
	)?;

The question that needs to be considered is whether to make the fat scie fully fat (Also include --invert-lazy cpython38). Although this question is probably easy to answer "no" to since 3.8 is only needed for Pants < 2.5 which is quite old at this point, it gets harder to answer when Pants switches to using CPython 3.11. At that point there will be very recent versions of Pants that need 3.9; so the fat variant including both cpython39 and cpython311 distributions (but still probably not cpython38) may make more sense.

I'll leave all this for others to kvetch over and implement.