Statements incorrectly reported as missing with FastAPI and async SQLAlchemy

[rfleschenberg]

Describe the bug

When using coverage in a FastAPI project that uses SQLAlchemy and asyncpg, parts of the code are wrongly reported as not covered. I know that the affected code statements do run, because otherwise the tests would fail. I also checked this by setting debugger breakpoints.

My tests so far indicate that this only happens if the test goes through a FastAPI router function. If I instead call the affected function directly, the coverage report is correct.

Unfortunately the most minimal MRE I was able to come up with involves Postgres and a bunch of dependencies. Sorry about that. On the other hand, I think my stack is not that exotic, so probably sooner or later others will also run into this issue.

To Reproduce
What version of Python are you using?

I tested with Python 3.7.3 and Python 3.9.6.

What version of coverage.py are you using? The output of coverage debug sys is helpful.

-- sys -------------------------------------------------------
               coverage_version: 6.0.2
                coverage_module: /home/rene/.virtualenvs/csa/lib/python3.7/site-packages/coverage/__init__.py
                         tracer: -none-
                        CTracer: available
           plugins.file_tracers: -none-
            plugins.configurers: -none-
      plugins.context_switchers: -none-
              configs_attempted: .coveragerc
                                 setup.cfg
                                 tox.ini
                                 pyproject.toml
                   configs_read: -none-
                    config_file: None
                config_contents: -none-
                      data_file: -none-
                         python: 3.7.3 (default, Jan 22 2021, 20:04:44) [GCC 8.3.0]
                       platform: Linux-4.19.0-18-amd64-x86_64-with-debian-10.11
                 implementation: CPython
                     executable: /home/rene/.virtualenvs/csa/bin/python3
                   def_encoding: utf-8
                    fs_encoding: utf-8
                            pid: 1704
                            cwd: /home/rene/projects/coverage-sqlalchemy-async
                           path: /home/rene/.virtualenvs/csa/bin
                                 /usr/lib/python37.zip
                                 /usr/lib/python3.7
                                 /usr/lib/python3.7/lib-dynload
                                 /home/rene/.virtualenvs/csa/lib/python3.7/site-packages
                    environment: HOME = /home/rene
                                 PYENV_ROOT = /home/rene/.pyenv
                                 PYENV_SHELL = zsh
                                 PYTHONDONTWRITEBYTECODE = 1
                                 PYTHONSTARTUP = /home/rene/.pystartup
                   command_line: /home/rene/.virtualenvs/csa/bin/coverage debug sys
                sqlite3_version: 2.6.0
         sqlite3_sqlite_version: 3.27.2
             sqlite3_temp_store: 0
        sqlite3_compile_options: COMPILER=gcc-8.3.0; ENABLE_COLUMN_METADATA; ENABLE_DBSTAT_VTAB
                                 ENABLE_FTS3; ENABLE_FTS3_PARENTHESIS; ENABLE_FTS3_TOKENIZER
                                 ENABLE_FTS4; ENABLE_FTS5; ENABLE_JSON1
                                 ENABLE_LOAD_EXTENSION; ENABLE_PREUPDATE_HOOK; ENABLE_RTREE
                                 ENABLE_SESSION; ENABLE_STMTVTAB; ENABLE_UNLOCK_NOTIFY
                                 ENABLE_UPDATE_DELETE_LIMIT; HAVE_ISNAN; LIKE_DOESNT_MATCH_BLOBS
                                 MAX_SCHEMA_RETRY=25; MAX_VARIABLE_NUMBER=250000; OMIT_LOOKASIDE
                                 SECURE_DELETE; SOUNDEX; TEMP_STORE=1
                                 THREADSAFE=1; USE_URI

What versions of what packages do you have installed? The output of pip freeze is helpful.

anyio==3.3.3
asgiref==3.4.1
asyncpg==0.24.0
attrs==21.2.0
certifi==2021.10.8
charset-normalizer==2.0.7
click==8.0.3
coverage==6.0.2
fastapi==0.70.0
flake8==4.0.1
greenlet==1.1.2
h11==0.12.0
httpcore==0.13.7
httpx==0.19.0
idna==3.2
importlib-metadata==4.2.0
iniconfig==1.1.1
mccabe==0.6.1
packaging==21.0
pkg-resources==0.0.0
pluggy==1.0.0
py==1.10.0
pycodestyle==2.8.0
pydantic==1.8.2
pyflakes==2.4.0
pyparsing==2.4.7
pytest==6.2.5
pytest-asyncio==0.15.1
rfc3986==1.5.0
sniffio==1.2.0
SQLAlchemy==1.4.25
starlette==0.16.0
toml==0.10.2
typing-extensions==3.10.0.2
uvicorn==0.15.0
zipp==3.6.0

What code are you running? Give us a specific commit of a specific repo that we can check out.

https://github.com/rfleschenberg/coverage-sqlalchemy-async/tree/ea17b8f9a3fddb1c62212803b6793aa4f9c63561

1. What commands did you run?

./runtests.sh

Expected behavior

A correct coverage report ;)

[rfleschenberg]

I realize that this is probably FastAPI-specific, but I thought you might still be interested in a report. Feel free to close it, of course.

[rfleschenberg]

Someone hinted me at #1082

So I guess this is a duplicate, sorry :)