BUG: 1D slices over extension types turn into N-dimensional slices over ExtensionArrays

[frreiss]

• closes BUG: 1D slices over extension types turn into N-dimensional slices over ExtensionArrays #42430
• tests added / passed
• Ensure all linting tests pass, see here for how to run them
• whatsnew entry

This PR contains a 1-line patch for issue #42430, plus a regression test to ensure the issue does not recur.

Before this change, ExtensionBlock. getitem_block_index() would request 2D slices of a block's underlying extension array, even though the __getitem__() method of ExtensionArray is (currently) only supposed to support 1D slicing. After the change, getitem_block_index() requests 1D slices. The change also fixes some linter/type checking errors.

[frreiss]

Looks like there was a single test failure on one of the CI builds. I'm not able to reproduce that failure on my machine. Can someone with the appropriate permissions rerun the pytest (actions-39-numpydev.yaml, not slow and not network, xsel, deprecate, -W error) build to see if the problem goes away by itself?

[jbrockmendel]

that should be fixed if you merge master

[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 1.3.x
$ git pull

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

$ git cherry-pick -m1 26e7c0f840197259f3af06a397df99b9b9f638a3

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

$ git commit -am 'Backport PR #42787: BUG: 1D slices over extension types turn into N-dimensional slices over ExtensionArrays'

4. Push to a named branch :

git push YOURFORK 1.3.x:auto-backport-of-pr-42787-on-1.3.x

5. Create a PR against branch 1.3.x, I would have named this PR:

"Backport PR #42787 on branch 1.3.x"

And apply the correct labels and milestones.

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

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

[jreback]

thanks @frreiss for the patch!

[jreback]

@meeseeksdev backport 1.3.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 1.3.x
$ git pull

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

$ git cherry-pick -m1 26e7c0f840197259f3af06a397df99b9b9f638a3

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

$ git commit -am 'Backport PR #42787: BUG: 1D slices over extension types turn into N-dimensional slices over ExtensionArrays'

4. Push to a named branch :

git push YOURFORK 1.3.x:auto-backport-of-pr-42787-on-1.3.x

5. Create a PR against branch 1.3.x, I would have named this PR:

"Backport PR #42787 on branch 1.3.x"

And apply the correct labels and milestones.

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

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

[jreback]

@frreiss if you wouldn't mind following the instructions above to manually backport this (above).

[simonjayhawkins]

conflicts due to #42422. manual backport done in #42850