Doctest ignores methods decorated with `functools.singledispatchmethod` #129578

viccie30 · 2025-02-02T13:03:16Z

Bug report

Bug description:

Doctest does not recognize tests in the docstrings of methods decorated with functools.singledispatchmethod. There's 2 causes:

It checks the dictionary of classes for functions and subclasses, thereby not invoking descriptors.

cpython/Lib/doctest.py

Lines 1061 to 1073 in df4a2f5

    
           if inspect.isclass(obj) and self._recurse: 
        
               for valname, val in obj.__dict__.items(): 
        
                   # Special handling for staticmethod/classmethod. 
        
                   if isinstance(val, (staticmethod, classmethod)): 
        
                       val = val.__func__ 
        
                   # Recurse to methods, properties, and nested classes. 
        
                   if ((inspect.isroutine(val) or inspect.isclass(val) or 
        
                         isinstance(val, property)) and 
        
                         self._from_module(module, val)): 
        
                       valname = '%s.%s' % (name, valname) 
        
                       self._find(tests, val, valname, module, source_lines, 
        
                                  globs, seen)

functools.singledispatchmethod does not call functools.update_wrapper on its instance, only on the wrapper function returned from its __get__ method.

A similar issue for cached_property was fixed in #107996.

Example

# mwe.py
import functools

class Class:
    @functools.singledispatchmethod
    def singledispatchmethod(self, arg):
        """
        >>> print(Class().singledispatchmethod(5))
        foo
        """
        return "foo"

    def regularmethod(self, arg):
        """
        >>> print(Class().regularmethod(5))
        foo
        """
        return "foo"

$ python3 -m doctest -v mwe.py
Trying:
    print(Class().regularmethod(5))
Expecting:
    foo
ok
2 items had no tests:
    mwe
    mwe.Class
1 item passed all tests:
   1 test in mwe.Class.regularmethod
1 test in 3 items.
1 passed.
Test passed.

doctest only finds one doctest, where there should be two.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Linux

Linked PRs

gh-129578: Fix collection of doctests from wrapped objects #129579

The text was updated successfully, but these errors were encountered:

viccie30 added the type-bug An unexpected behavior, bug, or error label Feb 2, 2025

viccie30 mentioned this issue Feb 2, 2025

gh-129578: Fix collection of doctests from wrapped objects #129579

Open

picnixz added the stdlib Python modules in the Lib dir label Feb 2, 2025

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Doctest ignores methods decorated with `functools.singledispatchmethod` #129578

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Doctest ignores methods decorated with functools.singledispatchmethod #129578

Doctest ignores methods decorated with functools.singledispatchmethod #129578

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Bug report

Bug description:

Example

CPython versions tested on:

Operating systems tested on:

Linked PRs

Doctest ignores methods decorated with `functools.singledispatchmethod` #129578

Doctest ignores methods decorated with `functools.singledispatchmethod` #129578