INSTALL: older version of petsc will cause error for building petsc4py

[scaomath]

Describe the error
I recently updated to a fresh install of Ubuntu 24.04, and installed petsc last month. Upon installing Firedrake today, I tried first using the environment variable pointing to the installed petsc (version 3.22.2). However, Firedrake installing script will give the following error:
Failed to build petsc4py ERROR: Could not build wheels for petsc4py, which is required to install pyproject.toml-based projects
Upon re-installing the correct version of petsc 4.23 according to pyproject.toml, everything is good. Note this is not necessarily a bug for Firedrake installing script. This issue is more like a feature request.

Steps to Reproduce

1. Install petsc with a version, say 3.22.2.
2. Install Firedrake by cloning the latest Github repo, with requirements pointing to a different version of petsc4py.
3. Building wheel will fail for petsc4py.

Expected behavior
I suggest adding some version check on petsc against the Python bindings petsc4py slepc4py used in pyproject.toml.

Environment:

• OS: Ubuntu 24.04
• Python version: I tried 3.11.12 first, then 3.10.17, the error persits so I figured it might be something else.

[connorjward]

I have added something in #4194, but this unfortunately isn't something Firedrake can truly fix. You would have observed the same issue if you had simply run

$ pip install petsc4py

By the time Firedrake is installing itself and can check this, petsc4py has either successfully installed or not.

[scaomath]

@connorjward That is true. That was how I figured out the version discrepancies in the first place. How about adding certain assertions for the version of petsc4py the same with the output of $PETSC_DIR/lib/petsc/bin/petscversion by creating an entrypoint in pyproject.toml? Something like https://setuptools.pypa.io/en/latest/userguide/entry_point.html

[connorjward]

I think I more or less do what you say in #4194 here, but that still won't address the issue of petsc4py not building.

Entrypoints are only available after the installation has completed, so I don't think they will quite work for this.

I think the 'right' solution is for petsc4py to do this check itself. You are more than welcome to submit an issue to them regarding this.

[scaomath]

Sounds good. Thanks.