Correct "stack test --coverage" results requires a "stack clean"

[mgsloan]

I found this while turning https://github.com/mgsloan/multi-test-suite into an integration test. Running stack test followed by stack test --coverage results in empty coverage reports. This appears to be an issue with GHC recompilation checking, as instead doing stack test --coverage --ghc-options -fforce-recomp solves the problem.

I'm not sure what to do about this. The best thing I can think of is a bit tricky - detect when this flag is newly enabled or disabled and supply --ghc-options --fforce-recomp for this circumstance.

[borsboom]

On OS X, the --ghc-options -fforce-recomp seems to trigger this build error:

ld: -rpath can only be used when creating a dynamic final linked image
clang: error: linker command failed with exit code 1 (use -v to see invocation)

[sjakobi]

Looks like #1997 is related, possibly a duplicate.

[mpilgrem]

The stack.yaml in the original repository was using lts-3.9 (GHC 7.10.2), which is no longer supported by modern Stack. I can't reproduce any problem with stack test followed by stack text --coverage, so I am going to close this issue.