cargo llvm-cov report --lcov fails: No filenames specified!

[DanielT]

I'm working on a Python module, implemented in Rust using PyO3 (this one: autosar-data-py)
Testing it using tests on the Rust side doesn't make sense; I wrote test in Python using pytest instead.
I would also like to generate code coverage from the pytest run.

The workflow for testing is:

1. create and activate a python virtualenv in the project
2. run maturin develop, which runs cargo build, builds the Python wheel and installs it into the virtualenv
3. run pytest

To gather coverage info I tried to:

1. Set RUSTFLAGS and LLVM_PROFILE_FILE as shown by cargo llvm-cov show-env --export-prefix
2. build the module and run pytest as above
3. run cargo llvm-cov report --lcov

This last command fails with the error message "No filenames specified!" and no coverage is generated.

[taiki-e]

Set RUSTFLAGS and LLVM_PROFILE_FILE as shown by cargo llvm-cov show-env --export-prefix

You have to set all env vars that show-env shows, not only two env vars.

[DanielT]

It looks like this only works on Linux, but not on Windows.
On windows I set all environment variables shown by show-env and still had the problem.

[taiki-e]

only works on Linux, but not on Windows.

Ah, if so, this is probably a duplicate of #300.

[taiki-e]

Closing as duplicate of #300 for now.

[taiki-e]

This should be fixed in 0.5.30 (#307).