doctest fails to collect tests from a C function that has been wrapped

[lpsinger]

Bug report

Bug description:

doctest.DocTestFinder is now failing to collect examples from functions that are defined in C and then wrapped. It still works just fine with functions that are defined in C but that are not wrapped.

This bug was introduced by #115440. It breaks doctests for Numpy ufuncs in pytest-doctestplus (see scientific-python/pytest-doctestplus#248).

I have placed reproducer code in this Gist: https://gist.github.com/lpsinger/65e59728555dc2096af88d394e2d4a6b. To reproduce, retrieve the code and run the following commands:

pip install -e .
python test.py

The script test.py fails with this error message:

$ python test.py 
Traceback (most recent call last):
  File "/Users/lpsinger/src/doctest-func-without-code/test.py", line 14, in <module>
    assert len(finder.find(bar.hello)[0].examples) == 1
               ^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/doctest.py", line 942, in find
    self._find(tests, obj, name, module, source_lines, globs, {})
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/doctest.py", line 1004, in _find
    test = self._get_test(obj, name, module, globs, source_lines)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/doctest.py", line 1072, in _get_test
    lineno = self._find_lineno(obj, source_lines)
             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.11/lib/python3.11/doctest.py", line 1121, in _find_lineno
    obj = inspect.unwrap(obj).__code__
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'builtin_function_or_method' object has no attribute '__code__'. Did you mean: '__call__'?

CPython versions tested on:

3.9

Operating systems tested on:

macOS

Linked PRs

• gh-117692: Fix AttributeError in DocTestFinder on wrapped builtin_or_method #117699
• [3.12] gh-117692: Fix AttributeError in DocTestFinder on wrapped builtin_or_method (GH-117699) #117708

[sobolevn]

Shorter repro on main:

>>> import binascii, doctest, functools
>>> def dec(func):
...    @functools.wraps(func)
...    def wrapper(*args, **kwargs):
...         return func(*args, **kwargs)
...    return wrapper
... 
>>> b = dec(binascii.b2a_hex)
>>> finder = doctest.DocTestFinder()
>>> finder.find(b)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
    finder.find(b)
    ~~~~~~~~~~~^^^
  File "/Users/sobolev/Desktop/cpython2/Lib/doctest.py", line 964, in find
    self._find(tests, obj, name, module, source_lines, globs, {})
    ~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython2/Lib/doctest.py", line 1026, in _find
    test = self._get_test(obj, name, module, globs, source_lines)
           ~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython2/Lib/doctest.py", line 1094, in _get_test
    lineno = self._find_lineno(obj, source_lines)
             ~~~~~~~~~~~~~~~~~^^^^^^^^^^^^^^^^^^^
  File "/Users/sobolev/Desktop/cpython2/Lib/doctest.py", line 1143, in _find_lineno
    obj = inspect.unwrap(obj).__code__
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'builtin_function_or_method' object has no attribute '__code__'. Did you mean: '__call__'?

[sobolevn]

Looks like I might have an idea on how to fix it! Thanks a lot for the report! 👍