Allow overriding of data file location

[jezdez]

For various reasons it'd be useful to be able to specify the location of the data file.

The path to the file was hard-coded in a14e746 which makes sense to fix the issue for sub-processes, but some environments don't allow writing to the CWD (certain Docker setups).

[ionelmc]

We could have an --cov-datapath option, or something to that effect.

Just out of curiosity, do you have an example of a project that is using a readonly mount in cwd?

[jezdez]

@ionelmc That sounds what I was looking for.

I don't have an easy to reproduce example at the moment, but the general gist is that we're trying to run tests in a Docker container with a command that is running as a non-privileged user and which has the app code (the host's CWD) mounted as a volume. The restrictions of Docker's volume implementation basically makes any volume owned by root inside the container. I realize that this is an edge case, but since coverage.py allows setting the data file as well and I don't see a reason for this to be hardcoded in pytest-cov, and I hoped this would be an easy fix®.

[ionelmc]

@jezdez is putting [run] data_file=/tmpsomething/.coverage in your coverage config not an option? For docker the path doesn't need to be very dynamic (you can mount wherever you want), thus it can sit just fine in a configuration file.

[jezdez]

@ionelmc That's what I tried first but then found the plugin to pass in a value manually which prevented it from working. I can check again, but I think it's safe to say that this is hardcoding .coverage right now.

[ionelmc]

Aaah, now I understand the actual problem: we don't take the datafile path from the coverage object - we just guess it with abspath('.coverage').

[jezdez]

@ionelmc Yep, apologies for not stating it more clearly at first.

[ionelmc]

Released 2.5.1.