File name does not match module name

Question

Newbie playing with haskell stack scripting and turtle.

• Created a folder stack-scripts. Thought if it looks good, then I'll create some haskell utils for me to replace bash scripts.

• Created a file named turtle.hs with following text:

  #!/usr/bin/env stack
  -- stack --resolver lts-11.2 script
  
  {-# LANGUAGE OverloadedStrings #-}
  
  import Turtle
  
  main = echo "Hello!"
  

• made the chmod +x turtle.hs and tried to execute it.

• Got the following error message:

  turtle.hs:1:1: error:
      File name does not match module name:
      Saw: `Main'
      Expected: `Turtle'
    |
  1 | #!/usr/bin/env stack
    | ^
  

It does what it should if I rename turtle.hs to turtle.sh. But then I have no syntax highlighting for haskell.

Also it works if I rename it to something-other.hs. But then Haskero (VSCode) complains about import Turtle line: Couldn't guess that module name. Does it exist?

What I'm missing here? Running in git bash on Windows.

Answer 1

Apparently you need to give the script a different name as the module name in which the code runs, will automatically be derived from it and now it will conflict with the imported Turtle module. Renaming it to turtlescript.hs and then

#!/usr/bin/env stack
-- stack --resolver lts-11.2 script --package turtle

{-# LANGUAGE OverloadedStrings #-}

import Turtle

main :: IO ()
main = echo "Hello!"

worked for me.