[python-package] Change build settings to set strict-config to false

[Jorricks]

Context

Setuptools recently introduced a new way for editable installations. Unfortunately, that does not work well with many tools at this moment in time, nor does it work well with a mono-repo. For that reason we choose to stick with the old way of doing editable installations which is shown here on setuptools docs.

pip install -e . --config-settings editable_mode=strict

(You will most likely see this appear on more places as people upgrade pip versions and the new way of editable installations becomes the default.)

Our code-base, of which we have 20+ different teams with different ML tooling, works as expected with this approach. Unfortunately, lightgbm is the exception.

In this MR

lightgbm throws an error on receiving the editable_mode=strict due to the strict-config = true.

ERROR: Unrecognized options in config-settings:
editable_mode -> Did you mean: editable?

There is no reason to throw errors on flags it does not understand, as it does not impact the compilation. Therefore I propose to set this value to False.

[borchero]

I'd be fine with it, wdyt @jameslamb?

[jameslamb]

There is no reason to throw errors on flags it does not understand, as it does not impact the compilation.

This is not correct.

The purpose of setting this to true is to catch exactly cases like this, where you're passing through a flag to the build backend that doesn't actually affect the build. With that set to false, the behavior becomes just silently ignoring it... in your case, maybe thinking you got an editable installation of lightgbm but not actually getting one, because you're passing a flag meant for setuptools through to `scikit-build-core.

That's been useful here, especially during active development changing how the Python library is packaged, to catch issues like typos in config settings.

At this stage, I'm ok with changing the value that for this in pyproject.toml as you've proposed, but let's please preserve that strictness in LightGBM's CI.

Please set environment variable SKBUILD_STRICT_CONFIG=true here:

LightGBM/.vsts-ci.yml

Line 10 in 5cd95a5

variables:

and here:

LightGBM/.github/workflows/python_package.yml

Line 16 in 5cd95a5

env:

and here:

LightGBM/.github/workflows/cuda.yml

Line 66 in 5cd95a5

env:

(that approach is documented at https://scikit-build-core.readthedocs.io/en/latest/configuration.html#other-options)

[Jorricks]

The purpose of setting this to true is to catch exactly cases like this, where you're passing through a flag to the build backend that doesn't actually affect the build. With that set to false, the behavior becomes just silently ignoring it... in your case, maybe thinking you got an editable installation of lightgbm but not actually getting one, because you're passing a flag meant for setuptools through to `scikit-build-core.

Good point. I was purely looking from a 'user' perspective but of course during development it helps tremendously if you are directly notified about inconsistencies or misspellings.

Thank you for pointing out the locations I needed to add the environment variable. Saved me a lot of time :). Also thanks for being flexible to directly consider the change.

[Jorricks]

@microsoft-github-policy-service agree

[jameslamb]

thanks very much.

It will likely be a while (on the order of months) until the next release of lightgbm. So for your builds where you're unconditionally passing setuptools config settings through to library installs, you'll still need to pass -C skbuild.strict-config=false.