A way to build cabal files with multiple executables that share the same exact build-depends, without repeating packages over and over again!

build_cabal_file.sh

#!/bin/bash

cabal_template="$1"
build_depends="$2"
test_build_depends="$3"

IFS=

handle_comma_ending () {
    local line
    local replacement_entry
    local whitespace
    local depends_file
    local file_init
    local file_last

    line="$1"
    replacement_entry="$2"
    depends_file="$3"

    replacement_regex="s/${replacement_entry}//g"
    whitespace=$(echo "$line" | sed -e $replacement_regex)
    file_init="$(head --lines=-1 $depends_file)"
    file_last="$(tail --lines=-1 $depends_file)"

    echo "$file_init" | sed -e "s/\(.*\)/`echo ${whitespace}`\1/g"
    echo "$file_last" | sed -e "s/\(.*\)/`echo ${whitespace}`\1,/g"
}

main () {
    while read line; do
        if [[ -f $build_depends ]] && [[ "$line" =~ '__DEPENDENCIES__,' ]]; then
            handle_comma_ending $line "__DEPENDENCIES__," $build_depends
        elif [[ -f $test_build_depends ]] && [[ "$line" =~ '__TEST_DEPENDENCIES__,' ]]; then
            handle_comma_ending $line "__TEST_DEPENDENCIES__," $test_build_depends
        elif [[ -f $build_depends ]] && [[ "$line" =~ '__DEPENDENCIES__' ]]; then
            whitespace=$(echo "$line" | sed -e 's/__DEPENDENCIES__//g')
            cat $build_depends | sed -e "s/\(.*\)/`echo ${whitespace}`\1/g"
        elif [[ -f $test_build_depends ]] && [[ "$line" =~ '__TEST_DEPENDENCIES__' ]]; then
            whitespace=$(echo "$line" | sed -e 's/__TEST_DEPENDENCIES__//g')
            cat $test_build_depends | sed -e "s/\(.*\)/`echo ${whitespace}`\1/g"
        else
            echo "$line"
        fi
    done < $cabal_template
}

main

build_depends

base                 >= 4.6 && <4.7,
aeson                == 0.6.1.0,
attoparsec           == 0.10.4.0,
bytestring           == 0.10.0.2,
blaze-builder        == 0.3.1.1,
conduit              == 1.0.7.3,
http-conduit         == 1.9.4.2,
http-reverse-proxy   == 0.2.0,
http-types           == 0.8.0,
lens                 == 3.9.0.2,
mtl                  == 2.1.2,
optparse-applicative >= 0.5.2,
regex-pcre           >= 0.94 && < 0.95,
regex-pcre-gsub      == 0.0.1.0,
network              == 2.4.1.2,
resourcet            == 0.4.7.2,
wai                  == 1.4.0.1,
warp                 >= 1.3.9,
maestro-config       == 0.1.0.0,

-- BROKEN DEPENDENCIES
containers           == 0.5.0.0,
entropy              == 0.2.1

Makefile

# Assuming all cabal gen files (myproject.cabal.tmpl, build_depends and test_build_depends) 
# are in gen/cabal/ folder

CABAL_FILE = myproject.cabal
CABAL_GEN_FILES = $(wildcard gen/cabal/*)

$(CABAL_FILE) : $(CABAL_GEN_FILES)
        @echo "Building new cabal file"
        @bin/build_cabal_file.sh \
          gen/cabal/maestro-proxy.cabal.tmpl \
          gen/cabal/build_depends \
          gen/cabal/test_build_depends > $(CABAL_FILE)

project.cabal.tmpl

name:                my-project
version:             0.0.1.0
-- synopsis:
-- description:
license:             MIT
license-file:        LICENSE
author:              Roman Gonzalez
maintainer:          [email protected]
-- copyright:
category:            Other
build-type:          Simple
-- extra-source-files:
cabal-version:       >=1.10

flag testloop
     description: Build testloop binary
     default: False

library
  default-language:    Haskell2010
  hs-source-dirs: src
  exposed-modules:
        MyProject.Internal
  build-depends:
        __DEPENDENCIES__

executable myproject-testloop
  default-language:    Haskell2010
  hs-source-dirs: src, test
  main-is: TestLoop.hs
  if flag(testloop)
    build-depends:
          __DEPENDENCIES__,
          __TEST_DEPENDENCIES__,
          testloop >= 0.1.1 && < 0.2
  else
    buildable: False

test-suite myproject-tests
  default-language:    Haskell2010
  type: exitcode-stdio-1.0
  hs-source-dirs: src, test
  main-is: TestSuite.hs
  build-depends:
       __DEPENDENCIES__,
       __TEST_DEPENDENCIES__

executable myproject-bin
  default-language:    Haskell2010
  main-is: Main.hs
  hs-source-dirs: src

  build-depends:
       __DEPENDENCIES__

test_build_depends

hspec    >= 1.7 && < 1.8,
HUnit    >= 1.2 && < 1.3