fix: support regular_to_jagged in Content._recursively_apply / ak.transform

[agoose77]

Fixes #2047

[codecov]

Codecov Report

Merging #2048 (b534427) into main (64377c1) will increase coverage by 0.01%.
The diff coverage is 100.00%.

Additional details and impacted files

Impacted Files	Coverage Δ
src/awkward/_do.py	83.72% <ø> (ø)
src/awkward/contents/content.py	73.13% <100.00%> (+0.38%)	⬆️
src/awkward/contents/regulararray.py	88.45% <100.00%> (+0.04%)	⬆️

[jpivarski]

This does seem like a good idea. Had it been a broadcast_and_apply argument that wasn't implemented in recursively_apply? If so, this is a good step toward further unification. regular_to_jagged is something one might want to do or not do, independent of whether there's only one array to recurse over or there are several arrays to broadcast together.

[jpivarski]

And yes, it can be merged.

[agoose77]

Had it been a broadcast_and_apply argument that wasn't implemented in recursively_apply? If so, this is a good step toward further unification.

I think so, at least, that's what it looked like. I didn't dig too deeply into the git blame, but it seems as though the broadcasting logic came directly from the C++, and we know that ak.transform is younger than that.

[jpivarski]

I do remember a regular_to_jagged boolean argument, and in this PR, it's pretty obvious that such an argument wasn't in recursively_apply until now, so I guess it must have been in broadcast_and_apply.