"Cabal repl" test isn't working correctly

[judah]

The cabal repl test effectively "fails" in CI, but doesn't block it from passing:
https://www.google.com/url?q=https://travis-ci.org/google/proto-lens/jobs/424489054&sa=D&source=hangouts&ust=1536177613202000&usg=AFQjCNFx5I7DlkoFRgsdjCHXJ04l3i3Paw

+cabal repl canonical_test
Preprocessing library for proto-lens-tests-0.1.0.1..
Building library for proto-lens-tests-0.1.0.1..
...
Ok, 3 modules loaded.
*Proto.Canonical> 
<interactive>:1:1: error:
    • Variable not in scope: main
    • Perhaps you meant ‘Prelude.min’ (imported from Data.ProtoLens.Runtime.Prelude)
*Proto.Canonical> Leaving GHCi.

It doesn't look like there's necessarily anything broken with proto-lens, but we should make the test pass. (Maybe check the output of the cabal repl command?)

[blackgnezdo]

The way I dealt with tests running in ghci is by having them write files for the test driver to validate. The file name to write into is generally passed as a parameter of :main.