"happy" is missing when following Stack install instructions

[owickstrom]

Describe the bug
It was reported by email. When following instructions for Stack installation, the happy command was reported missing.

To Reproduce
Follow installation instructions at https://owickstrom.github.io/komposition/user-guide/installation/#linux when on Debian (unstable).

Expected behavior
Should not require happy to be installed outside of Stack? Is this a bug in the Stack resolver or installation?

Desktop (please complete the following information):

• OS: Debian unstable
• Komposition version or commit: ?
• Build environment: Stack

Additional context

   Cabal-simple_mPHDZzAJ_2.2.0.1_ghc-8.4.3: The program 'happy' is required but
   it could not be found.

[akilegaspi]

Interestingly enough, I'm Debian unstable without happy parser generator and I can compile Komposition using stack install

Stack Version: 1.7.1

[owickstrom]

@akilegaspi OK, then maybe a difference in Stack versions. I didn't get that information, though.