using a test file named zlib.py never runs the test

[ebryerwork]

If the test file name is 'zlib.py', the test will not run; in the log will appear

[2021-12-10T10:39:08] verbose: reframe: Loaded 0 test(s)
[2021-12-10T10:39:08] verbose: reframe: Generated 0 test case(s)

If the test file is named anything else, it runs. I run ReFrame with the command ~/reframe/bin/reframe --run --purge-env --config-file ~/swst-icds-test/settings.py --checkpath ~/swst-icds-test/zlib.py -v. I have attached the test file and my settings file.
zlib_test.tar.gz

[ebryerwork]

Naming the file lxml.py does the same thing. The test won't run. It seems that naming the test file the same as a module that reframe is using is not a good idea. This is an edge case of course.

[vkarak]

I confirm that this is a bug and it can be very easily reproduced. Thanks for catching!

cp unittests/resources/checks/hellocheck.py unittests/resources/checks/zlib.py
./bin/reframe -c  unittests/resources/checks/zlib.py -l

Looking for tests in '/.../zlib.py'
Validating '/.../zlib.py': OK
No tests registered
Loaded 0 test(s)
Generated 0 test case(s)
Filtering test cases(s) by name: 0 remaining
Filtering test cases(s) by tags: 0 remaining
Filtering test cases(s) by other attributes: 0 remaining
Building and validating the full test DAG
Full test DAG:
  <empty>
Final number of test cases: 0
[List of matched checks]

Found 0 check(s)

[rsarm]

The problem it's happening here:
https://github.com/eth-cscs/reframe/blob/4485ad2f9d92795010037f9fa7dab7edd6de0e17/reframe/utility/__init__.py#L58-L59
At this point, the modules from external are already in sys.modules and the function will return instead of continuing to import the test with the same name.

The issue depends on where the test is with respect to reframe's install directory since in order to enter in that function it has to pass by a if rel_filename.startswith('..'):
https://github.com/eth-cscs/reframe/blob/4485ad2f9d92795010037f9fa7dab7edd6de0e17/reframe/utility/__init__.py#L88