Apply PIP_CONSTRAINT correctly

[hoodmane]

No description provided.

[agriyakhetarpal]

We could also do a 0.29.1 release with this change so that we don't need to use your fork in pyodide/pyodide#5162, please let me know if you'd like that!

[hoodmane]

We don't need to release just to merge then I can use the pyodide/pyodide-build commit on main.

[agriyakhetarpal]

Sure, just re-triggered the CI failure because I'm unsure if it was flaky or not. Please feel free to merge if it passes

[agriyakhetarpal]

Looks like a genuine failure.

[hoodmane]

Looks like a real failure to me.

[agriyakhetarpal]

I'm unable to reproduce this locally on macOS, the test passes for me. It's unrelated to pytest.

[ryanking13]

But pyodide/pyodide#5132 worked without this change. Why is this change needed?

[hoodmane]

I'm not entirely sure why the other fix worked, but notice that we do not pass build_env to install_reqs in any way. So if we don't set this as an enviornment variable, how would the pip install command know that we have the constraint?

[ryanking13]

PIP_CONSTRAINT is a host environment variable, so it should already be stored in os.environ without having to pass it in from build_env.

[hoodmane]

When I ran it locally I found os.environ["PIP_CONSTRAINT"] raised a KeyError at this spot.

[ryanking13]

Hmm, that's weird... 🤔

[hoodmane]

Can you try it out and see if you log os.environ["PIP_CONSTRAINT"] here? If it prints something for you maybe we can just close this.

[ryanking13]

Oh, you are right. It is slightly more complicated than I thought though. So what happens is:

1. Building packages in-tree with invoking make:

• Makefile will read and execute Makefile.envs, so PIP_CONSTRAINT is set in host env.

2. Building packages in-tree with invoking pyodide build-recipes.

• Makefile.envs will not be executed, so PIP_CONSTRAINT is not set in host env, but only stored in build env

3. Building packages out-of-tree

• Makefile.envs will not be executed, so PIP_CONSTARINT is not set in host env, but only stored in build env

So the current change looks okay. The reason why pyodide/pyodide#5132 worked is probably because we try again with build env replace when installing requirement fails.

[ryanking13]

Let's add a comment that this is only for in-tree build for future readers.

For OOT build, a user needs to set PIP_CONSTRAINT if needed.