Update for new Cabal

[treeowl]

We currently use deprecated cabal-install commands that are going away. Let's not.

[treeowl]

@phadej @hvr, I'm hoping maybe one of you could help out with this.

[phadej]

Simple solution doesn't work

% cabal new-build --enable-tests --enable-benchmarks
Resolving dependencies...
cabal: Could not resolve dependencies:
[__0] trying: containers-0.6.0.1 (user goal)
[__1] rejecting: containers:!test (constraint from config file, command line
flag, or user target requires opposite flag selection)
[__1] trying: containers:*test
[__2] next goal: ChasingBottoms (dependency of containers *test)
[__2] rejecting: ChasingBottoms-1.3.1.5 (cyclic dependencies; conflict set:
ChasingBottoms, containers)

with issue being haskell/cabal#4087

---

The workaround is to split tests and benchmarks into own package(s), used only in CI.

packages:
  containers/
  containers-tests/
  contaienrs-benchmarks/

That's straightforward thing to do, and both cabal v2-build and stack would work with this. One could say that downside is that say, Stackage, won't build tests and benchmarks, but it doesn't anyway so it doesn't matter. (Some Nix users might actually build container tests, but I doubt, as they'll need to solve circularity as well).

[treeowl]

Splitting tests and benchmarks into their own packages sounds very nice, but it has its own complication. Those packages will need to be built on top of a containers compiled for testing, which sounds like a bit of a mess. Will we need a custom CI script to handle it?

[phadej]

haskell-ci handles that with ease, e.g.

• https://github.com/dmwit/universe
• https://github.com/haskell-servant/servant

[treeowl]

I'm sorry, could you point me to the relevant parts? What I'm talking about is that running the containers tests and benchmarks requires containers to be compiled with -DTESTING, which is not how it should usually be compiled. We could probably change that, and maybe we should, but it will be extremely annoying. In particular, QuickCheck uses show to explain what failed; if we can't customize Show for testing, we'll need to work out another way to get QuickCheck to show us what we want.

[treeowl]

It seems this is mostly done, but the testing on GHC/Cabal head has been removed, presumably by mistake.

[treeowl]

@phadej, I'd appreciate your help restoring can-fail testing for ghc/cabal head. The new .travis.yml is too different from the old for me to know what to do with that; in particular all the env stuff is gone.

[phadej]

Do you really want to let CI fail for GHC HEAD? I suspect it will happen when you less want to track moving target?

[phadej]

Or did I misunderstood? Adding ghc-head job which can fail is relatively simple: I explained in #628

Making that job to be required, i.e. so whole build can fail is not supported.

[sjakobi]

I'll tentatively close this, since the setup has evolved a lot since the last activity here.

Please reopen if there's more to be addressed here.