haskell - Stack build fails due to missing package although stack ghci works

Question

I am trying to build a simple program in Haskell using stack. I created a new project using stack new and did a stack setup after that. The template builds fine.

I want to experiment with binary file parsing, so I imported Data.ByteString. My build-depends in the cabal file look like this:

build-depends:     base >= 4.7 && < 5
                 , bytestring >= 0.10.6
                 , binary >= 0.7.5

stack ghci now just works, but stack build is still not happy. Can someone tell me what I did wrong here?

Here is the complete error message:

test-0.1.0.0: build
Preprocessing library test-0.1.0.0...
In-place registering test-0.1.0.0...
Preprocessing executable 'test-exe' for test-0.1.0.0...

haskell/test/app/Main.hs:4:18:
    Could not find module ‘Data.ByteString’
    It is a member of the hidden package ‘bytestring-0.10.6.0@bytes_6VWy06pWzJq9evDvK2d4w6’.
    Perhaps you need to add ‘bytestring’ to the build-depends in your .cabal file.
    Use -v to see a list of the files searched for.

haskell/test/app/Main.hs:5:8:
    Could not find module ‘Data.Binary.Get’
    It is a member of the hidden package ‘binary-0.7.5.0@binar_3uXFWMoAGBg0xKP9MHKRwi’.
    Perhaps you need to add ‘binary’ to the build-depends in your .cabal file.
    Use -v to see a list of the files searched for.

--  While building package test-0.1.0.0 using:
      .stack/setup-exe-cache/x86_64-osx/setup-Simple-Cabal-1.22.5.0-ghc-7.10.3 --builddir=.stack-work/dist/x86_64-osx/Cabal-1.22.5.0 build lib:test exe:test-exe --ghc-options " -ddump-hi -ddump-to-file"
    Process exited with code: ExitFailure 1

and this is my app/Main.hs file:

module Main where

import Lib
import qualified Data.ByteString as B
import Data.Binary.Get
import Data.Word

main :: IO ()
main =  do
    putStrLn "f"

Thank you very much for your help.

Answer 1

This is likely because you added bytestring to the build-depends of the library, not the executable. One option to avoid needing to repeat these dependencies for the different stanzas is to use hpack as the package description format.