Haskell-ide-engine: GHC version support

[alanz]

I am experimenting with the new cabal-helper / ghc-mod in https://github.com/alanz/haskell-ide-engine/tree/bleeding-edge-c-h

It uses cabal-plan-0.5.0.0. Stack is unable to build this for GHC 8.2.1/8.2.2 because the Cabal bundled with the snapshot is 2.0.0.1 or something, and it does not understand the license field used in cabal-plan-0.5.0.0.

Not, it builds fine with cabal new-build, so long as it is version 2.4.1.0.

So, there are two options

1. When (eventually) this patch lands, drop support for GHC 8.2.x
2. Run a submodule of cabal-plan with the license changed.

I guess there is also

1. Request @hvr to move back to an older license format for cabal-plan-0.5.0.0.

Given the (not-so) imminent landing of GHC 8.8, I am leaning toward dropping support for GHC 8.2

Any opinions?

[hvr]

it builds fine with cabal new-build, so long as it is version 2.4.1.0.

I don't think that's accurate. It's supposed to build as long as you have cabal-2.2.x or newer, which is far from being bleeding edge, and supports GHCs back till GHC 7.0.

Request @hvr to move back to an older license format for cabal-plan-0.5.0.0.

While I understand that you're trying to workaround design flaws of Stack & Stackage with respect to its handling of the cabal spec, I don't think we should hold back everyone just to workaround limitations in Stack. This would set a very bad precedent.

[fendor]

Closed by #1430