Debugging pytest test method fails on dap.continue() but works with dep.test_method()

[PhilippFeO]

Hey,

I recently set up nvim-dap and nvim-dap-python and everything works fine on normal Python files.

When I want to debug a pytest test function with dap.continue() it starts, ie. dap-ui loads but everything is terminated after a short flash of the UI printing 'Session terminated'. In contrast, invoking with dap.test_method() does the job, ie. dap-ui loads and the program halts on the breakpoint. Any hints are welcome!

My configuration

nvim-dap-python

local dap_python = require('dap-python')
-- dap.continue does not work, test_method() does
dap_python.setup('~/.venv/debugpy/bin/python')
dap_python.test_runner = 'pytest'

I have no pytest.ini in my project.

pip list

I tinkered around with different virtual environments. Here is the one of the project I wish to be able to debug with. (To be honest, currently it is not obvious to me when nvim-dap-python finds the virtual env via $VIRTUAL_ENV itself and when not.)

Package        Version
-------------- -------
debugpy        1.8.0
exceptiongroup 1.2.0
iniconfig      2.0.0
markdown-it-py 3.0.0
mdurl          0.1.2
packaging      23.2
pip            22.0.2
pluggy         1.4.0
Pygments       2.17.2
pytest         7.4.4
PyYAML         6.0.1
rich           13.7.0
setuptools     59.6.0
tomli          2.0.1
wcwidth        0.2.12

And also pip list of ~/.venv/debugpy/bin/activate:

Package    Version
---------- -------
debugpy    1.8.0
pip        22.0.2
setuptools 59.6.0

I hope these information are sufficient. Let me know, in case you need more!

---

Thank you for your work!

[PhilippFeO]

Time passed and I have figured it out. I had to add the following to my config:

require('dap').configurations.python = {
    {
        name = "Pytest: Current File",
        type = "python",
        request = "launch",
        module = "pytest",
        args = {
            "${file}",
            "-sv",
            -- "--log-cli-level=INFO",
            -- "--log-file=test_out.log"
        },
        console = "integratedTerminal",
    }
}

I was also able to reproduce my issue above on non-test methods. dap.continue() runs the file, ie. debugging a method doesn't work if it is not called, fi. in a if __name__ == '__main__': block. dap.test_method() does what I expected from dap.continue(). Although spending a decent amount of time on informing about debugging in Neovim (YouTube, docs). This was not obvious to me – but makes sense now (like everything makes sense retrospectively). And to be honest, when my issue arised, I hadn't perfect working examples – again, obvious retrospectively.

---

I will leave this issue open in case some flaws arise since I am still exploring the plugin and don't feel confident enough. You can either close the issue, when I provided the correct solution. Otherwise, I will do it next week. And again, thank you for making debugging in Neovim possible :rocket:

[mfussenegger]

The default "Launch file" configuration from nvim-dap-python will run the file similarly to if it would've been launched in the command line via python <myfile>.py, so if you use it on a test module it won't work unless it has an entry point.

E.g. for plain unittest you could import the main function and call that within a if __name__ == '__main__': block (https://docs.python.org/3/library/unittest.html#unittest.main)

But your solution to add a dedicated pytest configuration is also fine and has the advantage that it works without changes to pytest files

[PhilippFeO]

Thank you for answering such a beginners question :)