DEPR: 'A' for yearly frequency and YearEnd in favour of 'Y'

[natmokval]

xref #54275, #54061

deprecated string 'A' for yearly frequency and YearEnd in favour of 'Y'.

EDIT:
deprecated annual frequencies with various fiscal year ends: "A-DEC", "A-JAN", etc. in favour of "Y-DEC", "Y-JAN", etc.

[MarcoGorelli]

in offsets.pyx I think you'll need to generalise this part

                if is_period is False and name == "M":
                    warnings.warn(
                        "\'M\' will be deprecated, please use \'ME\' "
                        "for \'month end\'",
                        UserWarning,
                        stacklevel=find_stack_level(),
                    )
                    name = "ME"
                if is_period is True and name == "ME":
                    raise ValueError(
                        r"for Period, please use \'M\' "
                        "instead of \'ME\'"
                    )
                elif is_period is True and name == "M":
                    name = "ME"

[natmokval]

in offsets.pyx I think you'll need to generalise this part

                if is_period is False and name == "M":
                    warnings.warn(
                        "\'M\' will be deprecated, please use \'ME\' "
                        "for \'month end\'",
                        UserWarning,
                        stacklevel=find_stack_level(),
                    )
                    name = "ME"
                if is_period is True and name == "ME":
                    raise ValueError(
                        r"for Period, please use \'M\' "
                        "instead of \'ME\'"
                    )
                elif is_period is True and name == "M":
                    name = "ME"

Thank you for the comment. I generalised it by adding a dictionary with frequencies deprecated for offsets.

[natmokval]

I deprecated annual frequencies with various fiscal year ends: "A-DEC", "A-JAN", etc. in favour of "Y-DEC", "Y-JAN", etc., added tests for FutureWarning and notes in v2.2.0. @MarcoGorelli, could you please take a look at this PR?

[MarcoGorelli]

same as in the other PR, it's not clear to me why this moved down - could you explain please?

[natmokval]

because I wanted to keep this together with line 4668: offset = _get_offset(prefix) where we use this prefix. There is no need to do it, I can move it back.

[MarcoGorelli]

yeah that might be better - wouldn't we risk missing the if prefix in {"D", "H", "min", "s", "ms", "us", "ns"}: like this?

[natmokval]

hmm, I agree, we might have problems if frequency is 'T', 'S', 'L', 'U', or 'N'. Maybe we should check
if prefix in c_DEPR_ABBREVS: before we are doing if prefix in {"D", "H", "min", "s", "ms", "us", "ns"}:
I will update my PR

[natmokval]

I moved the check if prefix in c_DEPR_ABBREVS: back to line 4642 and added a test that fails if the order of the checks isn't correct.

[MarcoGorelli]

added a test that fails if the order of the checks isn't correct.

this is music to my ears - well done!

[MarcoGorelli]

solid work! let's get this in and move on to the next one 💪

[natmokval]

Thank you for helping me with this PR.