Solver cabal install hint

[adrianwong]

Resolves #3841.

Recover from all errors on invoking proc "cabal" --numeric-version.

This reintroduces the helpful hint to stack install cabal-install if stack solver is run when cabal is not on PATH, instead of displaying the exception message propagated from RIO (thanks for the help, @mgsloan!).

• Any changes that could be relevant to users have been recorded in the ChangeLog.md
• The documentation has been updated, if necessary.

Please also shortly describe how you tested your change. Bonus points for added tests!

• Ran stack solver on a project using an existing version of stack, with and without cabal on PATH
• Ran stack solver on the same project using the modified stack, with and without cabal on PATH. Verified that the helpful hint was displayed without cabal on PATH; verified that stack solver ran without issue with cabal on PATH

[dbaynard]

Thanks, @adrianwong. Would you like some more newcomer-friendly issues to tackle?

[adrianwong]

@dbaynard If it's within my ability as a Haskell scrub, I'm keen. I was thinking of tackling #3863 next, but I'm open to suggestions.

[dbaynard]

That's good to hear. Tackle the ones that appeal (and please do continue to note that you'll be working on the issue)!

[dbaynard]

(I just wanted to make clear I'd reviewed this — I should have added myself as reviewer earlier)

[madnight]

Hmm, when i run stack install cabal-install as suggested i get the following error:

solver must be one of: modular
CallStack (from HasCallStack):
  error, called at libraries/Cabal/Cabal/Distribution/ReadE.hs:49:24 in Cabal-2.2.0.1:Distribution.ReadE
ghcjs-boot: error running: /usr/bin/cabal --config-file /home/x/.ghcjs/x86_64-linux-0.2.1.9007019-8.0.1/ghcjs/cabalBootConfig --ignore-sandbox install ./boot/ghc-prim --solver=topdown --global --ghcjs --one-shot --avoid-reinstalls --builddir dist --with-compiler /home/x/.stack/programs/x86_64-linux/ghcjs-0.2.1.9007019_ghc-8.0.1/src/.stack-work/install/x86_64-linux-tinfo6/lts-7.19/8.0.1/bin/ghcjs --with-hc-pkg /home/x/.stack/programs/x86_64-linux/ghcjs-0.2.1.9007019_ghc-8.0.1/src/.stack-work/install/x86_64-linux-tinfo6/lts-7.19/8.0.1/bin/ghcjs-pkg --prefix /home/x/.ghcjs/x86_64-linux-0.2.1.9007019-8.0.1/ghcjs --enable-documentation --haddock-html --haddock-hyperlink-source --enable-shared --enable-library-profiling -v2 --dry-run
exit status: 1
stderr: solver must be one of: modular
CallStack (from HasCallStack):
  error, called at libraries/Cabal/Cabal/Distribution/ReadE.hs:49:24 in Cabal-2.2.0.1:Distribution.ReadE

[dbaynard]

@madnight That ghcjs-boot line jumps out (see #4086). I'd like to see the stack.yaml and .cabal files you're using.

[madnight]

@dbaynard i fixed it by switching to nix build, which was a suggestion from irc, i'm not even sure if the current ghcjs master can be build with stack

[dbaynard]

Some aspects of ghcjs (probably setting up the ghcjs, though not using ghcjs) are in the process of being deprecated #4086.