DM-53178: Ignore sqlite resource warnings in tests

[timj]

This doesn't fix the warnings from pytest-cov with scons -jN. Maybe we need to set PYTHONWARNINGS env var instead.

cc/ @andy-slac

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 81.81%. Comparing base (637bcd0) to head (1d79d41).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #138      +/-   ##
==========================================
- Coverage   85.36%   81.81%   -3.55%     
==========================================
  Files           5        2       -3     
  Lines          41       33       -8     
  Branches        3        3              
==========================================
- Hits           35       27       -8     
  Misses          3        3              
  Partials        3        3              

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[andy-slac]

Looks OK. I tried to understand where that remaining warning comes from and I found a big mess in pytest and pytest-cov handling of warnings:

• For some stupid reasons pytest-cov think that they need to enable warnings for
  sqlite ResourceWarnings.
• But they check existing warning filters to see if there is already a filter for that warning. They check for message re.compile('unclosed database in <sqlite3.Connection object at', re.I), if that filter exists, they don't add a new filter.
• When you use -W option or PYTHONWARNINGS with ignore:unclosed database in <sqlite3.Connection object at:ResourceWarning string, the message string is escaped before it is compiled, and the result is re.compile('unclosed\\ database\\ in\\ <sqlite3\\.Connection\\ object\\ at', re.I), which does not match what pytest-cov expects.
• Another complication (that helps us) is that pytest uses -W... option to set temporary filters for each test case, which masks pytest-cov filter. But after all test cases are done, garbage collection kills sqlite connection and at that point it generates ResourceWarning, but with pytest-cov filter is active again.

Also, if you add

[tool.pytest.ini_options]
filterwarnings = [
    "default",
    "ignore:unclosed database in <sqlite3.Connection object at:ResourceWarning",
]

to pyproject.toml then the string is not escaped before compiling into re, and it does match what pytest-cov expects. But that does not help us very much as this needs to be added to each package that uses buler in tests.

I think we need to make a ticket for pytest-cov guys.

[andy-slac]

I made a PR for pytest-cov: pytest-dev/pytest-cov#727

[timj]

I had tried putting the filterwarnings in the pyproject.toml but it didn't work if -Wd was used.

[andy-slac]

I had tried putting the filterwarnings in the pyproject.toml but it didn't work if -Wd was used.

filterwarnings needs to be done in addition to -W "ignore:... to suppress few remaining warnings (basically to force pytest-cov not to add its filter).