Strange behavior with ProcessPoolExecutor

[0x0L]

Hello,

I don't have simple reproducible example but the same tox suite running pytest --cov --cov-append reports slightly differently in py37 and py38.

I set up my .coveragerc as follows

[path]
source =
    src
    */site-packages
    *\site-packages

[run]
branch = true
parallel = true
source =
    my_package
    tests

Running in py37 correctly report the code under src/my_package and tests
In py38, i see additional lines .tox/py38/.../site-packages/my_package/*.py. The only hits for those files are actually callback code called in a ProcessPoolExecutor

I tried setting concurrency = multiprocessing but it didn't help.

As a workaround, I'm omitting these files when reporting but it's still puzzling as it only happens with 3.8 :)

[nedbat]

It's hard to know what's going on without being able to reproduce it myself, but here are some thoughts:

• Are you sure your package is installed in site-packages in both 3.7 and 3.8?
• Can you run coverage with --debug=trace? That will show what files are being considered for measurement.

[0x0L]

Hi,

Thanks for getting back to me.
I setup a repo at https://github.com/0x0L/testcov
I'm able to reproduce it locally on my machine

tox 3.20.1

---------- coverage: platform darwin, python 3.7.9-final-0 -----------
Name                    Stmts   Miss Branch BrPart     Cover   Missing
----------------------------------------------------------------------
src/gruik/__init__.py       6      0      0      0   100.00%
tests/test_a.py             3      0      0      0   100.00%
----------------------------------------------------------------------
TOTAL                       9      0      0      0   100.00%

---------- coverage: platform darwin, python 3.8.3-final-0 -----------
Name                                                      Stmts   Miss Branch BrPart     Cover   Missing
--------------------------------------------------------------------------------------------------------
.tox/py38/lib/python3.8/site-packages/gruik/__init__.py       6      2      0      0    66.67%   9-10
src/gruik/__init__.py                                         6      0      0      0   100.00%
tests/test_a.py                                               3      0      0      0   100.00%
--------------------------------------------------------------------------------------------------------
TOTAL                                                        15      2      0      0    86.67%

[nedbat]

Hmm, I can reproduce the behavior, but I don't understand why it would be different for the two versions. It might have to do with how multiprocessing is implemented?

[0x0L]

It definitely looks like it but I see no mention of any change to the ProcessPool in the release notes for 3.8

[0x0L]

@nedbat
Actually the issue is not python 3.8 specific. In the example repo https://github.com/0x0L/testcov I added py39 and changed the order of the envlist.

With envlist = clean,py39,py37,py38,report, I get

---------- coverage: platform darwin, python 3.9.1-final-0 -----------
Name                    Stmts   Miss Branch BrPart     Cover   Missing
----------------------------------------------------------------------
src/gruik/__init__.py       6      0      0      0   100.00%
tests/test_a.py             3      0      0      0   100.00%
----------------------------------------------------------------------
TOTAL                       9      0      0      0   100.00%

---------- coverage: platform darwin, python 3.7.9-final-0 -----------
Name                                                      Stmts   Miss Branch BrPart     Cover   Missing
--------------------------------------------------------------------------------------------------------
.tox/py37/lib/python3.7/site-packages/gruik/__init__.py       6      5      0      0    16.67%   1-4, 8-10
src/gruik/__init__.py                                         6      0      0      0   100.00%
tests/test_a.py                                               3      0      0      0   100.00%
--------------------------------------------------------------------------------------------------------
TOTAL                                                        15      5      0      0    66.67%

---------- coverage: platform darwin, python 3.8.5-final-0 -----------
Name                                                      Stmts   Miss Branch BrPart     Cover   Missing
--------------------------------------------------------------------------------------------------------
.tox/py37/lib/python3.7/site-packages/gruik/__init__.py       6      5      0      0    16.67%   1-4, 8-10
.tox/py38/lib/python3.8/site-packages/gruik/__init__.py       6      2      0      0    66.67%   9-10
src/gruik/__init__.py                                         6      0      0      0   100.00%
tests/test_a.py                                               3      0      0      0   100.00%
--------------------------------------------------------------------------------------------------------
TOTAL                                                        21      7      0      0    66.67%