Path decorators: allow empty docstrings to support embedded Python

newsfragments/2987.issue.rst

@@ -0,0 +1 @@
+Fix crash when importing trio in embedded Python on Windows, and other installs that remove docstrings.

src/trio/_path.py

@@ -38,12 +38,12 @@ async def wrapper(*args: P.args, **kwargs: P.kwargs) -> T:
  return await run_sync(partial(fn, *args, **kwargs))
 
  update_wrapper(wrapper, wrapped)
- assert wrapped.__doc__ is not None
- wrapper.__doc__ = (
- f"Like :meth:`~{wrapped.__module__}.{wrapped.__qualname__}`, but async.\n"
- f"\n"
- f"{cleandoc(wrapped.__doc__)}\n"
- )
+ if wrapped.__doc__:
+  wrapper.__doc__ = (
+  f"Like :meth:`~{wrapped.__module__}.{wrapped.__qualname__}`, but async.\n"
+  f"\n"
+  f"{cleandoc(wrapped.__doc__)}\n"
+  )
  return wrapper
 
  return decorator
@@ -76,23 +76,23 @@ def _wrap_method_path_iterable(
  def wrapper(self: PathT, /, *args: P.args, **kwargs: P.kwargs) -> Iterable[PathT]:
  return map(self.__class__, [*fn(self._wrapped_cls(self), *args, **kwargs)])
 
- assert wrapper.__doc__ is not None
- wrapper.__doc__ += (
- f"\n"
- f"This is an async method that returns a synchronous iterator, so you\n"
- f"use it like:\n"
- f"\n"
- f".. code:: python\n"
- f"\n"
- f" for subpath in await mypath.{fn.__name__}():\n"
- f" ...\n"
- f"\n"
- f".. note::\n"
- f"\n"
- f" The iterator is loaded into memory immediately during the initial\n"
- f" call (see `issue #501\n"
- f" <https://github.com/python-trio/trio/issues/501>`__ for discussion).\n"
- )
+ if wrapper.__doc__:
+  wrapper.__doc__ += (
+  f"\n"
+  f"This is an async method that returns a synchronous iterator, so you\n"
+  f"use it like:\n"
+  f"\n"
+  f".. code:: python\n"
+  f"\n"
+  f" for subpath in await mypath.{fn.__name__}():\n"
+  f" ...\n"
+  f"\n"
+  f".. note::\n"
+  f"\n"
+  f" The iterator is loaded into memory immediately during the initial\n"
+  f" call (see `issue #501\n"
+  f" <https://github.com/python-trio/trio/issues/501>`__ for discussion).\n"
+  )
  return wrapper
 
 

src/trio/_tests/test_path.py

@@ -252,3 +252,21 @@ async def test_classmethods() -> None:
 
  # Wrapped method has docstring
  assert trio.Path.home.__doc__
+
+
+@pytest.mark.parametrize(
+ "wrapper",
+ [
+ trio._path._wraps_async,
+ trio._path._wrap_method,
+ trio._path._wrap_method_path,
+ trio._path._wrap_method_path_iterable,
+ ],
+)
+def test_wrapping_without_docstrings(
+ wrapper: Callable[[Callable[[], None]], Callable[[], None]]
+) -> None:
+ @wrapper
+ def func_without_docstring() -> None: ... # pragma: no cover
+
+ assert func_without_docstring.__doc__ is None