[dairiki]

This fixes #551.

This is an alternative to #552.

Here, in order to bypass the restriction forbidding capturing groups in re.Scanner in Python 3.15, we essentially vendor re.Scanner from Python 3.14.

The code in re.Scanner has been essentially unchanged from Python 2.5 through Python 3.14, modulo changes in module naming and the introduction of the RegexFlag enum. The only change in Python 3.15 is the addition of the check for capturing groups. Since it's been so stable, I'm guessing that this vendoring of code from a previous release is fairly safe.

Note that crashes due to segmentation faults mentioned as the motivation for introducing the capturing group ban in Python 3.15 (python/cpython@fa9c3ee) seem only to be an issue when named capturing groups are used. (Ref: python/cpython#140797, python/cpython#140944.)

[Edited to add more detail about the history of re.Scanner.]

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.05%. Comparing base (f1221ce) to head (9c4c68c).

Additional details and impacted files

@@            Coverage Diff             @@
##               v2     #553      +/-   ##
==========================================
+ Coverage   99.03%   99.05%   +0.01%     
==========================================
  Files          19       20       +1     
  Lines        1248     1270      +22     
==========================================
+ Hits         1236     1258      +22     
  Misses         12       12              

Flag	Coverage Δ
unittests	99.05% <100.00%> (+0.01%)	⬆️

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