Fix jupyterlab downgrade issue on extension installation

[Sarthug99]

References

Fixes #15277

Code changes

Created a temporary constraint file using tempfile.NamedTemporaryFile. I obtained the current JupyterLab version and enforced it as a constraint. This constraint is then passed to the pip install command using the --constraint flag, so that any plugin installation is in line with the existing JupyterLab version.

User-facing changes

User won't face the issue of JupyterLab getting downgraded on installation of certain plugins, as was the case before.

Backwards-incompatible changes

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[krassowski]

@fcollonval can you help me out here, I did not catch why we need to use constrain here over just a requirement?

[fcollonval]

@fcollonval can you help me out here, I did not catch why we need to use constrain here over just a requirement?

in this specific case we could use a requirement. But what we want to achieve is actually add the extension as requirement with some constraints on the dependencies.

As stated in the documentation:

Constraints files are requirements files that only control which version of a requirement is installed, not whether it is installed or not.

So using a constraint is more aligned with the intent here.

[fcollonval]

Thanks @Sarthug99

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[krassowski]

@meeseeksdev please backport to 4.0.x

[lumberbot-app]

Owee, I'm MrMeeseeks, Look at me.

There seem to be a conflict, please backport manually. Here are approximate instructions:

1. Checkout backport branch and update it.

git checkout 4.0.x
git pull

2. Cherry pick the first parent branch of the this PR on top of the older branch:

git cherry-pick -x -m1 26677ad4e0654f5fc7627c44b3c4d98707bbd0b2

3. You will likely have some merge/cherry-pick conflict here, fix them and commit:

git commit -am 'Backport PR #15650: Fix jupyterlab downgrade issue on extension installation'

4. Push to a named branch:

git push YOURFORK 4.0.x:auto-backport-of-pr-15650-on-4.0.x

5. Create a PR against branch 4.0.x, I would have named this PR:

"Backport PR #15650 on branch 4.0.x (Fix jupyterlab downgrade issue on extension installation)"

And apply the correct labels and milestones.

Congratulations — you did some good work! Hopefully your backport PR will be tested by the continuous integration and merged soon!

Remember to remove the Still Needs Manual Backport label once the PR gets merged.

If these instructions are inaccurate, feel free to suggest an improvement.