BUG: Negative freq in date_range produces values out of start and endpoints

[jrmylow]

• closes BUG: Negative freq in date_range produces values out of start and endpoints #56147
• Tests added and passed if fixing a bug or adding a new feature
• All code checks passed.
• Added type annotations to new arguments/methods/functions.
• Added an entry in the latest doc/source/whatsnew/vX.X.X.rst file if fixing a bug or adding a new feature.

[jrmylow]

pre-commit.ci autofix

[MarcoGorelli]

thanks, taking a look next week - could you fix up the conflicts please?

[jrmylow]

pre-commit.ci autofix

[jrmylow]

Awaiting #56873 to fix the test failure in:

__________________ test_api_categorical[postgresql_adbc_conn] __________________
[gw0] linux -- Python 3.9.18 /home/runner/micromamba/envs/test/bin/python3.9
[XPASS(strict)] categorical dtype not implemented for ADBC postgres driver

[jrmylow]

whoops I didn't mean to delete that, will try to rectify

[github-actions]

This pull request is stale because it has been open for thirty days with no activity. Please update and respond to this comment if you're still interested in working on this.

[MarcoGorelli]

this is probably fine, I just haven't had a chance yet to check how (in?)consistently negative ranges are currently handled. I'm aiming to get this in by 3.0 if it's ready

[MarcoGorelli]

I think you're right, this is the fix

could you add a whatsnew note for 3.0 please?

could you also update the date_range docs please? they currently don't account for negative frequencies, they just say

Returns the range of equally spaced time points (where the difference between any two adjacent points is specified by the given frequency) such that they all satisfy start <[=] x <[=] end,

If we're changing negative freq behaviour, we need to be very explicit on what the rules are

[jrmylow]

pre-commit.ci autofix

[MarcoGorelli]

thanks @jrmylow , CI failure is unrelated

[mroeschke]

Thanks @jrmylow