Module with TemplateHaskell doesn't recompile when it should

[tom-audm]

tl;dr: a module with TemplateHaskell that should have been recompiled wasn't.

$ cabal --version
cabal-install version 2.2.0.0

$ mkdir /tmp/th_recompile
$ cd /tmp/th_recompile
$ git init
Initialized empty Git repository in /tmp/th_recompile/.git/

Then add these files:

th-recompile.cabal:

name:                th-recompile
version:             0.1.0.0
license:             BSD3
build-type:          Simple
cabal-version:       >=1.10

executable th-recompile
  main-is:
    Main.hs
  other-modules:
    Hash
  other-extensions:
    TemplateHaskell
  build-depends:
      base <5
    , gitrev
  -- hs-source-dirs:
  default-language:
    Haskell2010

Hash.hs:

{-# LANGUAGE TemplateHaskell #-}

module Hash where

import Development.GitRev

printIt = print $(gitHash)

Main.hs:

{-# LANGUAGE TemplateHaskell #-}
import Development.GitRev

import Hash

main = do
   print $(gitHash)
   printIt

Setup.hs:

import Distribution.Simple
main = defaultMain

$ git add Main.hs Hash.hs th-recompile.cabal Setup.hs
$ git commit -m 'Init'
$ cabal new-run
Resolving dependencies...
Build profile: -w ghc-8.4.4 -O1
In order, the following will be built (use -v for more details):
 - th-recompile-0.1.0.0 (exe:th-recompile) --enable-profiling (first run)
Configuring executable 'th-recompile' for th-recompile-0.1.0.0..
Preprocessing executable 'th-recompile' for th-recompile-0.1.0.0..
Building executable 'th-recompile' for th-recompile-0.1.0.0..
[1 of 2] Compiling Hash             ( Hash.hs, /tmp/th_recompile/dist-newstyle/build/x86_64-linux/ghc-8.4.4/th-recompile-0.1.0.0/x/th-recompile/build/th-recompile/th-recompile-tmp/Hash.dyn_o )
[2 of 2] Compiling Main             ( Main.hs, /tmp/th_recompile/dist-newstyle/build/x86_64-linux/ghc-8.4.4/th-recompile-0.1.0.0/x/th-recompile/build/th-recompile/th-recompile-tmp/Main.dyn_o )
[1 of 2] Compiling Hash             ( Hash.hs, /tmp/th_recompile/dist-newstyle/build/x86_64-linux/ghc-8.4.4/th-recompile-0.1.0.0/x/th-recompile/build/th-recompile/th-recompile-tmp/Hash.p_o )
[2 of 2] Compiling Main             ( Main.hs, /tmp/th_recompile/dist-newstyle/build/x86_64-linux/ghc-8.4.4/th-recompile-0.1.0.0/x/th-recompile/build/th-recompile/th-recompile-tmp/Main.p_o )
Linking /tmp/th_recompile/dist-newstyle/build/x86_64-linux/ghc-8.4.4/th-recompile-0.1.0.0/x/th-recompile/build/th-recompile/th-recompile ...
"2b46b5914d9f51a7f3f2e94001c96f4ebda05b07"
"2b46b5914d9f51a7f3f2e94001c96f4ebda05b07"
$ echo '' >> Main.hs
$ git add Main.hs
$ git commit -m 'Trivial'
$ cabal new-run
Build profile: -w ghc-8.4.4 -O1
In order, the following will be built (use -v for more details):
 - th-recompile-0.1.0.0 (exe:th-recompile) --enable-profiling (file Main.hs changed)
Preprocessing executable 'th-recompile' for th-recompile-0.1.0.0..
Building executable 'th-recompile' for th-recompile-0.1.0.0..
[2 of 2] Compiling Main             ( Main.hs, /tmp/th_recompile/dist-newstyle/build/x86_64-linux/ghc-8.4.4/th-recompile-0.1.0.0/x/th-recompile/build/th-recompile/th-recompile-tmp/Main.dyn_o )
[2 of 2] Compiling Main             ( Main.hs, /tmp/th_recompile/dist-newstyle/build/x86_64-linux/ghc-8.4.4/th-recompile-0.1.0.0/x/th-recompile/build/th-recompile/th-recompile-tmp/Main.p_o )
Linking /tmp/th_recompile/dist-newstyle/build/x86_64-linux/ghc-8.4.4/th-recompile-0.1.0.0/x/th-recompile/build/th-recompile/th-recompile ...
"456c2795231983904d57c62c48e255bc557b0f2a"
"2b46b5914d9f51a7f3f2e94001c96f4ebda05b07"

(Hash.hs should have been recompiled but it wasn't)

[phadej]

Duplicate of #4746