fix: refactor column selection logic for Polars

[jrycw]

Related to #340, pola-rs/polars#16242, pola-rs/polars#16250.

This PR provides a quick fix for the column selection logic in Polars. Further investigation may be needed from the team.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 85.74%. Comparing base (b290e66) to head (7a7f825).
Report is 10 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #360      +/-   ##
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+ Coverage   84.72%   85.74%   +1.02%     
==========================================
  Files          41       41              
  Lines        4346     4328      -18     
==========================================
+ Hits         3682     3711      +29     
+ Misses        664      617      -47     

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[machow]

Shoot, thanks for catching this! It seems like there are three behaviors in the new polars release that broke our current approach (afaict this is just a side-effect of us living on the bleeding edge of expand_selector() 😈 ):

1. quick fix: expand_selector() no longer accepts a list
2. quick fix: expand_selector() no long accepts a raw string or int
3. bigger discussion: expand_selector() only sometimes considers .exclude() a selector

I've opened an issue on polars RE the .exclude() behavior:

• Following a selector with .exclude() is not considered a selector pola-rs/polars#16448

[machow]

Thanks so much for the fixes (within 24 hours of the polars release 🤯 ). I hope it's okay, I tweaked a little bit to...

• try and give a detailed error for when a list has things that aren't selectors
• use functools reduce to accumulate selectors

We're going to make a small tweak to our CI, so we can quickly preview the docs builds for PRs off of forks, like this. And then should be able to merge!

[machow]

Here is the docs preview I've pushed to a branch:

https://docs-preview-test--gt-python.netlify.app/articles/intro.html

[jrycw]

@machow and @rich-iannone , everything looks great. It seems the developers from Polars are actively supporting and clarifying our use case, which is fantastic.