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Misleading exception message from pathlib.PurePath() when mixing str and bytes arguments #103525

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barneygale opened this issue Apr 13, 2023 · 4 comments
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3.12 bugs and security fixes topic-pathlib type-bug An unexpected behavior, bug, or error

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@barneygale
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barneygale commented Apr 13, 2023

Since 6716254, attempting to create a pathlib.PurePath or Path object with mixed str and bytes arguments raises a TypeError (yay!) with a misleading message (booo!):

>>> import pathlib
>>> pathlib.Path('foo', b'bar')
TypeError: Can't mix strings and bytes in path components

This message implies that bytes are supported, as long as we don't mix them with strings. And yet when we try that:

>>> pathlib.Path(b'foo', b'bar')
TypeError: argument should be a str or an os.PathLike object where __fspath__ returns a str, not 'bytes'

This message is better, and should be used in the former case.

Linked PRs

@barneygale barneygale added type-bug An unexpected behavior, bug, or error 3.12 bugs and security fixes topic-pathlib labels Apr 13, 2023
barneygale added a commit to barneygale/cpython that referenced this issue Apr 13, 2023
Check that arguments are strings before calling `os.path.join()`.

Also improve performance of `PurePath(PurePath(...))` while we're in the
area: we now use the *unnormalized* string path of such arguments.
barneygale added a commit to barneygale/cpython that referenced this issue Apr 13, 2023
Check that arguments are strings before calling `os.path.join()`.

Also improve performance of `PurePath(PurePath(...))` while we're in the
area: we now use the *unnormalized* string path of such arguments.
@terryjreedy
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terryjreedy commented Apr 13, 2023

The following

>>> pathlib.Path('foo', 1)
Traceback (most recent call last):
  File "C:\Programs\Python312\Lib\pathlib.py", line 703, in __init__
    super().__init__(*args)
  File "C:\Programs\Python312\Lib\pathlib.py", line 279, in __init__
    path = self._flavour.join(*args)
  File "<frozen ntpath>", line 149, in join
  File "<frozen genericpath>", line 164, in _check_arg_types
TypeError: join() argument must be str, bytes, or os.PathLike object, not 'int'

raises a message again implying that bytes would be accepted. It would be nicer if this also got the improved message about Path args.
ADDED: When the new code calls os.fspath(1), the message will be

expected str, bytes or os.PathLike object, not int
which still implies that bytes are accepted.

@barneygale
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barneygale commented Apr 13, 2023

That's possible to fix, but it involves either capturing and re-raising the TypeError, or basically re-implementing os.fspath(). This code is pretty performance-sensitive so I don't feel great about it.

Another option would be to add a string_only argument to os.fspath() that rejects bytes and raises an appropriate exception.

@barneygale
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That's possible to fix, but it involves either capturing and re-raising the TypeError, or basically re-implementing os.fspath(). This code is pretty performance-sensitive so I don't feel great about it

^ nevermind, I'm wrong. Thanks for the suggestion on the PR!

barneygale added a commit to barneygale/cpython that referenced this issue Apr 29, 2023
barneygale added a commit that referenced this issue May 2, 2023
…3526)

Check that arguments are strings before calling `os.path.join()`.

Also improve performance of `PurePath(PurePath(...))` while we're in the
area: we now use the *unnormalized* string path of such arguments.

Co-authored-by: Terry Jan Reedy <[email protected]>
@barneygale
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Fixed in #103526 / 8611e7b. Not backported as the bug only affects 3.12.

carljm added a commit to carljm/cpython that referenced this issue May 2, 2023
* main:
  pythongh-103822: [Calendar] change return value to enum for day and month APIs (pythonGH-103827)
  pythongh-65022: Fix description of tuple return value in copyreg (python#103892)
  pythonGH-103525: Improve exception message from `pathlib.PurePath()` (pythonGH-103526)
  pythongh-84436: Add integration C API tests for immortal objects (pythongh-103962)
  pythongh-103743: Add PyUnstable_Object_GC_NewWithExtraData (pythonGH-103744)
  pythongh-102997: Update Windows installer to SQLite 3.41.2. (python#102999)
  pythonGH-103484: Fix redirected permanently URLs (python#104001)
  Improve assert_type phrasing (python#104081)
  pythongh-102997: Update macOS installer to SQLite 3.41.2. (pythonGH-102998)
  pythonGH-103472: close response in HTTPConnection._tunnel (python#103473)
  pythongh-88496: IDLE - fix another test on macOS (python#104075)
  pythongh-94673: Hide Objects in PyTypeObject Behind Accessors (pythongh-104074)
  pythongh-94673: Properly Initialize and Finalize Static Builtin Types for Each Interpreter (pythongh-104072)
  pythongh-104016: Skip test for deeply neste f-strings on wasi (python#104071)
carljm added a commit to carljm/cpython that referenced this issue May 2, 2023
* main: (760 commits)
  pythonGH-104102: Optimize `pathlib.Path.glob()` handling of `../` pattern segments (pythonGH-104103)
  pythonGH-104104: Optimize `pathlib.Path.glob()` by avoiding repeated calls to `os.path.normcase()` (pythonGH-104105)
  pythongh-103822: [Calendar] change return value to enum for day and month APIs (pythonGH-103827)
  pythongh-65022: Fix description of tuple return value in copyreg (python#103892)
  pythonGH-103525: Improve exception message from `pathlib.PurePath()` (pythonGH-103526)
  pythongh-84436: Add integration C API tests for immortal objects (pythongh-103962)
  pythongh-103743: Add PyUnstable_Object_GC_NewWithExtraData (pythonGH-103744)
  pythongh-102997: Update Windows installer to SQLite 3.41.2. (python#102999)
  pythonGH-103484: Fix redirected permanently URLs (python#104001)
  Improve assert_type phrasing (python#104081)
  pythongh-102997: Update macOS installer to SQLite 3.41.2. (pythonGH-102998)
  pythonGH-103472: close response in HTTPConnection._tunnel (python#103473)
  pythongh-88496: IDLE - fix another test on macOS (python#104075)
  pythongh-94673: Hide Objects in PyTypeObject Behind Accessors (pythongh-104074)
  pythongh-94673: Properly Initialize and Finalize Static Builtin Types for Each Interpreter (pythongh-104072)
  pythongh-104016: Skip test for deeply neste f-strings on wasi (python#104071)
  pythongh-104057: Fix direct invocation of test_super (python#104064)
  pythongh-87092: Expose assembler to unit tests (python#103988)
  pythongh-97696: asyncio eager tasks factory (python#102853)
  pythongh-84436: Immortalize in _PyStructSequence_InitBuiltinWithFlags() (pythongh-104054)
  ...
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