stack install ghc-mod fails with dependencies conflicts on OSX 10.13.4

Question

When I try to install ghc-mod via stack I end up having these depencies conflicts

Error: While constructing the build plan, the following exceptions were encountered:

In the dependencies for ghc-mod-5.8.0.0:
    Cabal-2.0.1.1 from stack configuration does not match >=1.18 && <1.25  (latest matching version is 1.24.2.0)
    base-4.10.1.0 from stack configuration does not match >=4.6.0.1 && <4.10  (latest matching version is 4.9.1.0)
    cabal-helper must match <0.8 && >=0.7.3.0, but the stack configuration has no specified version  (latest matching version is 0.7.3.0)
    extra-1.6.8 from stack configuration does not match <1.6 && >=1.4  (latest matching version is 1.5.3)
    ghc-8.2.2 from stack configuration does not match >=7.6 && <8.2
    haskell-src-exts-1.20.2 from stack configuration does not match <1.20 && >=1.18  (latest matching version is 1.19.1)
    hlint-2.1.6 from stack configuration does not match <2.1 && >=2.0.8  (latest matching version is 2.0.15)
    monad-journal-0.8.1 from stack configuration does not match <0.8 && >=0.4  (latest matching version is 0.7.2)
    optparse-applicative-0.14.2.0 from stack configuration does not match >=0.13.0.0 && <0.14  (latest matching version is 0.13.2.0)
needed since ghc-mod is a build target.

Some different approaches to resolving this:

  * Consider trying 'stack solver', which uses the cabal-install solver to attempt to find some working build configuration. This can be convenient when dealing with many complicated constraint
    errors, but results may be unpredictable.

  * Recommended action: try adding the following to your extra-deps in /Users/mo/.stack/global-project/stack.yaml:

- Cabal-1.24.2.0
- base-4.9.1.0
- cabal-helper-0.7.3.0
- extra-1.5.3
- haskell-src-exts-1.19.1
- hlint-2.0.15
- monad-journal-0.7.2
- optparse-applicative-0.13.2.0

if I try to add the suggested extra deps like so

extra-deps:
- Cabal-1.24.2.0
- base-4.9.1.0
- cabal-helper-0.7.3.0
- extra-1.5.3
- haskell-src-exts-1.19.1
- hlint-2.0.15
- monad-journal-0.7.2
- optparse-applicative-0.13.2.0
- process-1.4.3.0
- either-4.4.1.1
- free-4.12.4

I end up having a loop like this

    Error: While constructing the build plan, the following exceptions were encountered:

In the dependencies for ghc-mod-5.8.0.0:
    base-4.10.1.0 from stack configuration does not match >=4.6.0.1 && <4.10  (latest matching version is 4.9.1.0)
    ghc-8.2.2 from stack configuration does not match >=7.6 && <8.2
needed since ghc-mod is a build target.

In the dependencies for haskell-src-exts-util-0.2.3:
    haskell-src-exts-1.19.1 from stack configuration does not match >=1.20.0  (latest matching version is 1.20.2)
needed due to ghc-mod-5.8.0.0 -> haskell-src-exts-util-0.2.3

In the dependencies for hlint-2.0.15:
    haskell-src-exts-1.19.1 from stack configuration does not match >=1.20 && <1.21  (latest matching version is 1.20.2)
needed due to ghc-mod-5.8.0.0 -> hlint-2.0.15

Some different approaches to resolving this:

  * Set 'allow-newer: true' to ignore all version constraints and build anyway.

  * Consider trying 'stack solver', which uses the cabal-install solver to attempt to find some working build configuration. This can be convenient when dealing with many complicated constraint
    errors, but results may be unpredictable.

  * Recommended action: try adding the following to your extra-deps in /Users/mo/.stack/global-project/stack.yaml:

- base-4.9.1.0
- haskell-src-exts-1.20.2

if i put - haskell-src-exts-1.20.2 they ask me for - haskell-src-exts-1.19.1 back and vice versa I can't figure out what to do about this dependency conflict, and also I tried to run stack resolver but it doesn't get me anywhere

Grishilda

Answer 1

The issue is that ghc-mod does not support newer versions of GHC, I believe the last supported version is GHC 8.0. You can try changing your Stack resolver to lts-8.24 or nightly-2017-06-28 (see the snapshots listed on ghc-mod's Stackage page).

Esplanade

I had to uninstall stack and reinstall it again, and then use stack resolver nightly-2017-06-28 in order for it to work thanks a lot! – Grishilda

For newbies like me, “changing your Stack resolver to lts-8.24” meant to edit your ~/.stack/global-project/stack.yaml and changing the resolver: value. Re-run stack install ghc-mod and it worked – Russel

Answer 2

Even easier, this worked for me: stack install ghc-mod --resolver lts-8.24

Mia

Answer 3

input command line:

stack install ghc-mod --resolver lts-8.24

it really helps.

Myungmyxedema