ValueError: illegal newline value on 0x85 (NEL)

In attempting to harmonize the path pie implementation with more modern constructs, I'm seeking also to utilize the newline argument to open instead of explicitly substituting characters.

When I do, however, I find that some tests start to fail when NEL is passed as a newline character:

$ py -c "open('foo', 'w', newline='\x85')"
Traceback (most recent call last):
  File "<string>", line 1, in <module>
ValueError: illegal newline value: …

At least in some contexts, Python recognizes NEL as a line separator:

>>> 'a\x85b\x1ec'.splitlines()
['a', 'b', 'c']

See also #66428 for some background.

According to the wikipedia article, a conforming application should honor a number of characters as newlines:

>>> newlines = '\x0a', '\x0b', '\x0c', '\x0d', '\x0d\x0a', '\u0085', '\u2028', '\u2029'
>>> for candidate in newlines:
...   try: x=open('foo', 'w', newline=candidate)
...   except ValueError: print('failed on', repr(candidate))
... 
failed on '\x0b'
failed on '\x0c'
failed on '\x85'
failed on '\u2028'
failed on '\u2029'

Commencez par le reproducer signalé de open(..., newline=...) et comparez-le à str.splitlines() pour les caractères de nouvelle ligne indiqués. Suivez la gestion des entrées/sorties texte de CPython pour la validation de newline, puis identifiez ou ajoutez les tests pertinents. Le travail est terminé lorsque les valeurs de newline prévues ont un comportement défini et testé, sans régression dans la traduction existante de newline.