Failure using --fixtures flag with pytest

[gudjonragnar]

I have a conftest.py file that is loading an image and creating a container using this plugin. It looks something like this:

image = fetch("image-name")

my_container = container(...)

@pytest.fixture
def some_other_fixture():
    ...

When I run pytest --fixtures <test-path> it fails showing this error:

INTERNALERROR> Traceback (most recent call last):
INTERNALERROR>   File "/var/as/venvs/callback/lib/python3.8/site-packages/_pytest/main.py", line 269, in wrap_session
INTERNALERROR>     session.exitstatus = doit(config, session) or 0
INTERNALERROR>   File "/var/as/venvs/callback/lib/python3.8/site-packages/_pytest/python.py", line 1497, in _showfixtures_main
INTERNALERROR>     available.sort()
INTERNALERROR> TypeError: '<' not supported between instances of 'NoneType' and 'str'

When i looked into the code and check this available list that is being sorted I see this:

(5, 'tests.conftest', 'tests/conftest.py:88', 'hostname', <FixtureDef argname='hostname' scope='module' baseid='tests'>)
(5, None, '<string>:5', 'image', <FixtureDef argname='image' scope='session' baseid='tests'>)
(5, 'tests.conftest', 'tests/conftest.py:98', 'rabbit_connections', <FixtureDef argname='rabbit_connections' scope='module' baseid='tests'>)
(5, None, '<string>:5', 'my_container', <FixtureDef argname='my_container' scope='package' baseid='tests'>)

As you can see the two lines containing image and my_container have None as their second value and the location is also weird.

The available list is being created here: https://github.com/pytest-dev/pytest/blob/master/src/_pytest/python.py#L1471

I think the issue might be related to the decorator handling in the plugin, but I haven't investigated it.

[Jc2k]

That kind of makes sense. The current method for generating fixtures relies on some grim eval to make some other part of pytest function correctly so it's location won't be a file. I guess that code needs amending to set some properties that a normal fixture would have...

[Jc2k]

My memory is a bit flakey but I think this might be related to the current setup?

#5

[gudjonragnar]

I guess you are referencing the build_fixture_function function in builder.py?

[Jc2k]

Yeah. So i had hoped it would be enough to make sure that that returns something with .__module__ set, but so far in my tests pytest still thinks its None regardless.

[Jc2k]

Sigh. pytest captures a copy of the fixture, so you can't mutate it after calling the pytest decorator.

So something like this fixes it for me:

diff --git a/pytest_docker_tools/builder.py b/pytest_docker_tools/builder.py
index bdb3a70..2bc959c 100644
--- a/pytest_docker_tools/builder.py
+++ b/pytest_docker_tools/builder.py
@@ -5,7 +5,7 @@ from .templates import find_fixtures_in_params, resolve_fixtures_in_params
 
 def build_fixture_function(callable, scope, wrapper_class, kwargs):
     name = callable.__name__
-    docstring = "Docker image"
+    docstring = name
     if "path" in kwargs:
         docstring = getattr(callable, "__doc__", "").format(**kwargs)
     fixtures = find_fixtures_in_params(kwargs).union({"request", "docker_client"})
@@ -15,13 +15,15 @@ def build_fixture_function(callable, scope, wrapper_class, kwargs):
         f"""
     import pytest
 
-    @pytest.fixture(scope=scope)
     def {name}({fixtures_str}):
         \'\'\'
         {docstring}
         \'\'\'
         real_kwargs = resolve_fixtures_in_params(request, kwargs)
         return _{name}(request, docker_client, wrapper_class=wrapper_class, **real_kwargs)
+
+    {name}.__module__ = callable.__module__
+    {name} = pytest.fixture(scope=scope)({name})
     """
     )
     globals = {