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I'm trying to lint a file with ghc-mod. I know ghc-mod uses hlint for this and I know that hlint accepts arguments to modify the suggestions it reports. For instance, this works just fine:

eric@linux-epth:total-beginner-haskell$ hlint src/Borrower.hs --hint=Generalise
src/Borrower.hs:44:3: Suggestion: Use mappend
Found:
getName br ++
" (" `mappend` show (getMaxBooks br) `mappend` " books)"
Why not:
getName br `Data.Monoid.mappend`
(" (" `mappend` show (getMaxBooks br) `mappend` " books)")

1 hint

Here's the format ghc-mod requires for passing arguments to hlint:

Usage: ghc-mod lint [-h|--hlintOpt ARG] FILE

But none of the variations below produce the hint shown above:

eric@linux-epth:total-beginner-haskell$ ghc-mod lint -h hint=Generalise src/Borrower.hs
eric@linux-epth:total-beginner-haskell$ ghc-mod lint --hlintOpt hint=Generalise src/Borrower.hs
eric@linux-epth:total-beginner-haskell$ ghc-mod lint --hlintOpt "--hint=Generalise" src/Borrower.hs
eric@linux-epth:total-beginner-haskell$ ghc-mod lint --hlintOpt '--hint=Generalise' src/Borrower.hs

What is the correct format to use with ghc-mod to pass arguments through it to hlint?

Thank you.

ericky
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1 Answers1

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It seems that it is a bug of ghc-mod:

Issue: https://github.com/DanielG/ghc-mod/issues/826

It's already fixed and merged to master, but not yet released.

Since the issue's milestone is v5.8.0.0, it may be fixed in that release.

I built the ghc-mod from latest master branch from Github, and confirmed that following command works:

$ ghc-mod lint src/Borrower.hs  --hlintOpt='--hint=Generalise.hs'
src/Borrower.hs:1:8: Suggestion: Use mappendFound:  getName br ++    " (" `mappend` show (getMaxBooks br) `mappend` " books)"Why not:  getName br `Data.Monoid.mappend`    (" (" `mappend` show (getMaxBooks br) `mappend` " books)"

Here's the step that I executed to build latest ghc-mod from Github.

$ git clone https://github.com/DanielG/ghc-mod
$ cd ghc-mod
$ stack init --ignore-subdirs --solver
$ stack build
ymonad
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  • thank you for your help. I used "stack install ghc-mod" to get ghc mod. I have: "ghc-mod version 5.6.0.0 compiled by GHC 8.0.1". Could you tell me how to build from Github master like you did? Thank you. – ericky Feb 13 '17 at 16:36
  • Great - thanks! One last question: does it make a difference which directory I clone the repo into? – ericky Feb 13 '17 at 22:52
  • @ericky I think not – ymonad Feb 13 '17 at 23:54