Profiled builds of haskell_doctest fail

[aherrmann]

Describe the bug Building a haskell_doctest target in profiling mode (-c dbg) fails.

To Reproduce

$ bazel build //tests/haskell_doctest:doctest-lib-all-success -c dbg
...
tests/haskell_doctest/Bar.hs:3:1: error:
    Could not find module ‘Foo’
    There are files missing in the ‘lib-a’ package,
    try running 'ghc-pkg check'.
    Use -v (or `:set -v` in ghci) to see a list of the files searched for.
  |
3 | import Foo (foo)
  | ^^^^^^^^^^^^^^^^
...

Expected behavior The build should succeed.

Environment

• OS name + version: Ubuntu 19.10
• Bazel version: 2.1.0
• Version of the rules: 04f22a04cb12f7782a9a2c581db5f4f564bf69fd

Additional context This seems to only affect modules that import other modules. While //tests/haskell_doctest:doctest-lib-all-success fails, //tests/haskell_doctest:doctest-lib succeeds. The difference is that the latter excludes the only module that has an import statement.

[guibou]

I suppose you are using stack_snapshot, hence when using -c dbg, your package database only contains -prof versions (hence static) of the packages. (That's why GHC complains about missing files).

If you add -prof to doctest_flags, this issues disappears, but then doctest fails because it cannot load static libraries by definition (it uses ghci).

Possible solutions I'm thinking about:

• build with -c dbg should provide dynamic and profiled libraries, hence doctest may load the dynamic ones.
• bazel transition may be used to disable -c dbg on its dependencies.

[Xophmeister]

n.b., Still reproducible as of a464b7e with Bazel 4.2.1 (not surprising, given the above comment)