Pytest-cov leaves .coverage.hostname.number.number data files if running tests against multiprocessing.Pool

Running pytest with coverage for tests against multiprocessing.Pool generates several data files, but not all of them are cleaned after. It looks similar to #100. Pool.join() doesn’t seem to change anything. Example filename .coverage.myhost.local.7582.948066

Here’s the repository to reproduce: https://github.com/manycoding/pytest_cov_pool_datafiles_250

Your operating system name and version: Mac OS Mojave 10.14 (18A391)

Any details about your local setup that might be helpful in troubleshooting:

pipenv shell; pipenv install

Pipfile

pytest = "*"
pytest-cov = "*"
pytest-mock = "*"
tox-pipenv = "*"
pytest-pythonpath = "*"

Detailed steps to reproduce the bug:

pytest --cov=src --cov-report=term-missing  tests/test_cov_pool.py

[ionelmc]

So this really simple trick (/s) makes the problem go away:

@@ -14,7 +14,8 @@ def get_items_with_pool(count: int, start_index: int = 0):
     processes_count = os.cpu_count()

     batch_size = math.ceil(count / processes_count)
-    with Pool(processes_count) as p:
+    p = Pool(processes_count)
+    try:
         results = p.starmap(
             get_items,
             zip(
@@ -24,10 +25,7 @@ def get_items_with_pool(count: int, start_index: int = 0):
         )
         for items_batch in results:
             items.extend(items_batch)
-    p.join()
+    finally:
+        p.close()
+        p.join()
     return items

For some reason Pool.__exit__ sends KILL in addition to TERM …

[ionelmc]

@GergelyKalmar please open a new issue and add details