gh-80667: Fix Tangut ideographs names in unicodedata

[wismill]

Fix Tangut ideographs names in unicodedata.

Partially fixes #80667.

• Issue: Bugs and inconsistencies in unicodedata #80667

[ghost]

All commit authors signed the Contributor License Agreement.

[arhadthedev]

@malemburg, @ezio-melotti as Unicode experts.

[wismill]

@malemburg @ezio-melotti kind reminder

[wismill]

@malemburg @ezio-melotti @arhadthedev kind reminder

[arhadthedev]

Another attempt: @corona10 as a developer who worked with the unicode part of Python via Asian scripts.

[SnoopJ]

I do not have review authority on CPython, but since this PR has been sitting for a few months, I thought I'd chime in to say it looks good to me in terms of functionality. I just discovered this PR because I just wrote some downstream code to work around the lack of support for this range.

The additional test looks a little complicated to me, it may be duplicating functionality from makeunicodedata.py, but the code added to the runtime is pretty much following the lead of the CJK stuff that already exists.

[SnoopJ]

I'm a little unsettled that this loop is duplicated from above, but I don't see a better way to do it aside from maybe some preprocessor abuse.

[wismill]

Yeah I agree. But since this MR has received very little attention, I am not going to dedicate time to this if there is no opportunity to merge it.

[wismill]

@SnoopJ thank you for your review, I resolved 2 items.

I am quite demotivated because no CPython reviewer has been able to review this in close to half a year.

@malemburg @ezio-melotti @arhadthedev @corona10 kind reminder 🙏

[rcgale]

If it wasn't already known, unicodedata.name(...) throws a ValueError for these ideographs. Seems like a worthwhile effort to merge this PR if it fixes that!

Example (tried in Python 3.10.8):

import unicodedata

try:
    tangut_ideograph_172fd = b"\xf0\x97\x81\x83".decode("utf8")
    unicodedata.name(tangut_ideograph_172fd)
except ValueError as e:
    raise ValueError(f"Couldn't handle Tangut ideograph {tangut_ideograph_172fd}") from e

Output:

Traceback (most recent call last):
  File "<input>", line 5, in <module>
ValueError: no such name

The above exception was the direct cause of the following exception:

Traceback (most recent call last):
  File "/Users/robert/miniforge3/envs/wikigit/lib/python3.10/code.py", line 90, in runcode
    exec(code, self.locals)
  File "<input>", line 7, in <module>
ValueError: Couldn't handle Tangut ideograph 𗁃
 

[SnoopJ]

If it wasn't already known, unicodedata.name(...) throws a ValueError for these ideographs. Seems like a worthwhile effort to merge this PR if it fixes that!

Yep, this PR includes changes to _getucname() that account for this, and do fix the issue. Against b2c4e92:

$ ./python 
Python 3.13.0a0 (remotes/wismill/wip/tangut-ideographs:b2c4e92767, Jul 26 2023, 16:57:00) [GCC 9.4.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import unicodedata
>>> unicodedata.name("\U000172fd")
'TANGUT IDEOGRAPH-172FD'

I think 172FD is a typo in your sample, though? The given bytes look like they encode U+17043 instead, and under this PR unicodedata.name() reports it that way.

[wismill]

If it wasn't already known, unicodedata.name(...) throws a ValueError for these ideographs.

@rcgale I find that unicodedata.name(c, None) with a test is a better pattern.

I think 172FD is a typo in your sample, though? The given bytes look like they encode U+17043 instead

@SnoopJ I confirm that, good catch!

[rcgale]

Yep, this PR includes changes to _getucname() that account for this, and do fix the issue. Against b2c4e92:

Thanks, I appreciate the confirmation! Nice to know the bug has been identified, and that there's already a fix implemented. I hope it can be released soon!

I think 172FD is a typo in your sample, though? The given bytes look like they encode U+17043 instead

Yes, it was a typo. I was encountering the same problem with several Tangut characters, and I probably copy/pasted the output from a different example.

[wismill]

Really disappointed by the lack of interest of the Python devs after such a long time.

[rogerbinns]

It wasn't clear to me if this PR was merged or superseded. It has not been merged and Tangut codepoints still give errors. They were added in Unicode 9.0 in 2016.

Python 3.13.0rc1 (main, Aug 18 2024, 07:50:03) [GCC 13.2.0] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import unicodedata
>>> print(unicodedata.name("\U00017123"))
Traceback (most recent call last):
  File "<python-input-1>", line 1, in <module>
    print(unicodedata.name("\U00017123"))
          ~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^
ValueError: no such name

[wismill]

@rogerbinns feel free to revive this PR.

[serhiy-storchaka]

Revived in #144789.

[serhiy-storchaka]

I apologize for not getting a review of this PR in time, @wismill. There are not many core developers, especially experts in Unicode. I am now determined to see the matter through to the end. Your PR was generally good, it only needed some updates because the surrounding code changed.