hpc program will error out when running "test --coverage" on conduit

[mgsloan]

While test --coverage works well with my other test multi-package repos, https://github.com/snoyberg/conduit seems to be problematic for it:

git clone https://github.com/snoyberg/conduit
cd conduit
stack init
stack test --coverage

A report is generated for resourcet, but not the other packages, due to errors that look like this:

Running /home/mgsloan/.ghc/bin/hpc markup /home/mgsloan/fpco/conduit/conduit-extra/.stack-work/dist/x86_64-linux/Cabal-1.18.1.5/hpc/test.tix --srcdir /home/mgsloan/fpco/conduit/cereal-conduit/ --srcdir /home/mgsloan/fpco/conduit/conduit-extra/ --srcdir /home/mgsloan/fpco/conduit/conduit/ --srcdir /home/mgsloan/fpco/conduit/network-conduit-tls/ --srcdir /home/mgsloan/fpco/conduit/resourcet/ --hpcdir .stack-work/dist/x86_64-linux/Cabal-1.18.1.5/hpc/.hpc/ --reset-hpcdirs exited with ExitFailure 1

hpc: can not find resourcet-1.1.5/Control.Monad.Trans.Resource.Internal in ["/home/mgsloan/fpco/conduit/resourcet//.stack-work/dist/x86_64-linux/Cabal-1.18.1.5/hpc/.hpc/","/home/mgsloan/fpco/conduit/network-conduit-tls//.stack-work/dist/x86_64-linux/Cabal-1.18.1.5/hpc/.hpc/","/home/mgsloan/fpco/conduit/conduit//.stack-work/dist/x86_64-linux/Cabal-1.18.1.5/hpc/.hpc/","/home/mgsloan/fpco/conduit/conduit-extra//.stack-work/dist/x86_64-linux/Cabal-1.18.1.5/hpc/.hpc/","/home/mgsloan/fpco/conduit/cereal-conduit//.stack-work/dist/x86_64-linux/Cabal-1.18.1.5/hpc/.hpc/"]
Writing: resourcet-1.1.5/Data.Acquire.Internal.hs.html

This was quite puzzling, because /home/mgsloan/fpco/conduit/resourcet//.stack-work/dist/x86_64-linux/Cabal-1.18.1.5/hpc/.hpc/resourcet-1.1.5/Control.Monad.Trans.Resource.Internal.mix does exist. In order to figure out what's going on, I tracked these error messages down to this function in GHC: https://github.com/ghc/packages-hpc/blob/fb14d3428ba24d36e779736989dae3092a50a957/Trace/Hpc/Mix.hs#L87

It turns out that this error is emitted in a bunch of different cases... I've put down a TODO item to report and possibly fix this in ghc. I'm pretty sure the issue in this particular case is a mismatch in the module hash code in the tix file and the mix file:

The tix file has TixModule "resourcet-1.1.5/Control.Monad.Trans.Resource.Internal" 3767668384

Whereas the mix file that refers to has Mix "./Control/Monad/Trans/Resource/Internal.hs" 2015-07-16 02:48:09.660237209 UTC 3983615699

I have no idea why the tix file would ever end up with a different version that the mix file.

[mgsloan]

Note that this is no longer an issue with the current code, but will return if #664 is implemented. So, deferring to a later milestone.

[mgsloan]

Closing this out for now and putting a note on #664.