Ignore tests that touch the filesystem if sandboxed.

[Alexhuszagh]

Adds an environment variable CROSS_SANDBOXED that skips tests that touch the filesystem if set.

Closes #943.

[Alexhuszagh]

I think using an #[ignore] attribute is the best solution, since we still want to be able to run the tests if desired on NixOS, and there might be other scenarios where access to the filesystem is denied other than just NixOS. Adding it to the build script feels a bit overkill.

[Emilgardis]

I wish there was a way to make ignore configurable with envvars or something. I'm fine with this, however I'd prefer it to be not ignored unconditionally. A runtime skip maybe?

[Alexhuszagh]

I wish there was a way to make ignore configurable with envvars or something. I'm fine with this, however I'd prefer it to be not ignored unconditionally. A runtime skip maybe?

Sure, we could look for NIX_PATH, which is always set. And we could check for another envvar to not skip it if present. This way, it can still be tested. The other way is to add it based on the envvar to the build script, and do #[cfg_attr(nixos, ignore)]. That's probably the better solution, but I initially wanted to skip that.

[Alexhuszagh]

Ok I've added a check for NIX_PATH in the build script, however, this will not work in interesting cases if the build script somehow isn't run on NixOS but the actual code is compiled on NixOS. However, I think that's a rare enough possibility that this should be fine since it's only in a unit test for this to be true, would have to be outside the nix-build setting.

[Emilgardis]

worst case for that, just pass --ignored

[Alexhuszagh]

@otavio I've added the CROSS_SANDBOXED environment variable, which if set skips any tests that touch the filesystem. Seem good? This is checked in the build script.

[Alexhuszagh]

@otavio Does this look good? Does the use of an environment variable work for you, since this is quite a useful test to ensure our mount paths are correct?

[otavio]

It should work; I cannot try it today but will do once I have an opportunity.

[otavio]

We can merge this and I handle this in NixOS side.

[Alexhuszagh]

bors r=Emilgardis,otavio

[bors]

Build succeeded:

• conclusion