Arbitrary.WithExceptions: Too many open files

[edsko]

Example run:

$ cabal run test-grapesy -- -p Arbitrary.WithExceptions --quickcheck-tests=1000
grapesy
  Prop
    Test.Prop.Dialogue
      Arbitrary
        WithExceptions
          connPerRPC: FAIL (1.45s)
            *** Failed! Exception: 'Network.Socket.accept: resource exhausted (Too many open files)' (after 597 tests and 1 shrink):
            DialogueWithExceptions (UnnormalizedDialogue [])
            GlobalSteps {getGlobalSteps = []}
            Use --quickcheck-replay="(SMGen 2488985887102302335 10295797329131458171,96)" to reproduce.
            Use -p '/Arbitrary.WithExceptions/&&/connPerRPC/' to rerun this test only.
          sharedConn: FAIL
            *** Failed! Exception: 'Network.Socket.accept: resource exhausted (Too many open files)' (after 1 test and 1 shrink):
            DialogueWithExceptions (UnnormalizedDialogue [])
            GlobalSteps {getGlobalSteps = []}
            Use --quickcheck-replay="(SMGen 7677182066308157554 12389343332662471367,0)" to reproduce.
            Use -p '/Arbitrary.WithExceptions/&&/sharedConn/' to rerun this test only.

This happens only with the WithExceptions tests, not with the regular tests, and it also doesn't happen (at least, I haven''t seen it) when running fewer tests. I think this is a regression, didn't use to happen.

[edsko]

Moving this to high priority as it can affect non-test code also; file handles are scarce resources that we should be careful with. Not sure if this is a regression in grapesy itself or in a dependency.

[edsko]

See kazu-yamamoto/http2#151 for an analysis of what is happening.