I would like to make a change to os.fspath().
Specifically, os.fspath() currently raises an exception if something
besides str, bytes, or os.PathLike is passed in, but makes no checks
if an os.PathLike object returns something besides a str or bytes.
I would like to change that to the opposite: if a non-os.PathLike is
passed in, return it unchanged (so no change for str and bytes); if
an os.PathLike object returns something that is not a str nor bytes,
raise.
An example of the difference in the lzma file:
Current code (has not been upgraded to use os.fspath() yet)
-----------------------------------------------------------
if isinstance(filename, (str, bytes)):
if "b" not in mode:
mode += "b"
self._fp = builtins.open(filename, mode)
self._closefp = True
self._mode = mode_code
elif hasattr(filename, "read") or hasattr(filename, "write"):
self._fp = filename
self._mode = mode_code
else:
raise TypeError(
"filename must be a str or bytes object, or a file"
)
Code change if using upgraded os.fspath() (placed before above stanza):
filename = os.fspath(filename)
Code change with current os.fspath() (ditto):
if isinstance(filename, os.PathLike):
filename = os.fspath(filename)
My intention with the os.fspath() function was to minimize boiler-plate
code and make PathLike objects easy and painless to support; having to
discover if any given parameter is PathLike before calling os.fspath()
on it is, IMHO, just the opposite.
There is also precedent for having a __dunder__ check the return type:
--> class Huh:
... def __int__(self):
... return 'string'
... def __index__(self):
... return b'bytestring'
... def __bool__(self):
... return 'true-ish'
...
--> h = Huh()
--> int(h)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: __int__ returned non-int (type str)
--> ''[h]
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: __index__ returned non-int (type bytes)
--> bool(h)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: __bool__ should return bool, returned str
Arguments in favor or against?
--
~Ethan~
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