[doctests] Namespace packages (PEP 420) missing, leading to errors with relative imports

[punitchandra]

When testing packages with implicit namespace and using --doctest-module the doc test module is imported without the implicit namespace.

This causes problems as the module can gets imported with different name. Once with the proper path and once with missing the namespace.

My pytest related versions:
pytest (3.5.0)
pytest-attrib (0.1.3)
pytest-cov (2.5.1)
pytest-forked (0.2)
pytest-timeout (1.2.1)
pytest-xdist (1.22.2)

OS is Windows 7.
Please look at the example:

foo.zip

[pytestbot]

GitMate.io thinks possibly related issues are #603 (monkeypatch does not work on already-imported function), #181 (--pdb does not work when collecting), #275 (doctest does not consider usefixtures in pytest.ini), #605 (tmpdir.join("foo").write(...) doesn't work as expected.), and #478 (--pyargs does not understand namespace packages).

[nicoddemus]

Unfortunately pytest currently lacks support for namespace packages.

Related: #1927 and #478

[punitchandra]

#1927 is related to relative imports with implicit namespace. This is documented as not being supported here. This issue is with doctest and absolute imports in implicit namespace. It will help if it is clarified in the documentation that pytest does not support doctest for implicit namespace.
Also is there any plan to add this support?

[nicoddemus]

Hi @punitchandra, there are no specific plans for this feature. We have very loose plans since we have very little man-power, unfortunately.

If you want to help out though, you are more than welcome. We would love to guide you through a PR if you have the time.

[jaraco]

I believe the issue is illustrated by this exercise I just ran:

~ $ cd ~/draft
draft $ ls
draft $ mkdir pkg
draft $ touch pkg/__init__.py
draft $ cat > pkg/mod.py
"""
>>> print(__name__)
pkg.mod
"""
draft $ pip-run -q pytest -- -m pytest --doctest-modules
========================================================== test session starts ==========================================================
platform darwin -- Python 3.9.0, pytest-6.2.1, py-1.10.0, pluggy-0.13.1
rootdir: /Users/jaraco/draft
collected 1 item                                                                                                                        

pkg/mod.py .                                                                                                                      [100%]

=========================================================== 1 passed in 0.03s ===========================================================
draft $ rm pkg/__init__.py
draft $ pip-run -q pytest -- -m pytest --doctest-modules
========================================================== test session starts ==========================================================
platform darwin -- Python 3.9.0, pytest-6.2.1, py-1.10.0, pluggy-0.13.1
rootdir: /Users/jaraco/draft
collected 1 item                                                                                                                        

pkg/mod.py F                                                                                                                      [100%]

=============================================================== FAILURES ================================================================
_____________________________________________________________ [doctest] mod _____________________________________________________________
001 
002 >>> print(__name__)
Expected:
    pkg.mod
Got:
    mod

/Users/jaraco/draft/pkg/mod.py:2: DocTestFailure
======================================================== short test summary info ========================================================
FAILED pkg/mod.py::mod
=========================================================== 1 failed in 0.02s ===========================================================