Create custom flags in Haskell

Question

I have a test suite which runs the same test cases with two backends: the in-memory one and the real one, I am trying to create a function which only run the real one when a flag is present.

I have seen it from time to time in Prelude but I cannot make it work.

I would more or less be as following:

onFullSuite :: Spec -> Spec
#if defined(RUN_FULL_SUITE)
onFullSuite = id
#else
onFullSuite = xdescribe "Only on full test suite run"
#endif

Do you have any hints on the missing parts?

How do you compile this? – Willem Van Onsem Oct 03 '20 at 18:33 — Willem Van Onsem, Oct 03 '20 at 18:33
Did you add `{-# LANGUAGE CPP #-}` at the head of the file? – Willem Van Onsem Oct 03 '20 at 19:25 — Willem Van Onsem, Oct 03 '20 at 19:25

score 2 · Accepted Answer · answered Oct 11 '20 at 14:50

It is a two steps process:

create a cabal flag
conditionally define it as ghc-option

flags:
  run-full-suite:
    manual: true
    default: false


library:
  source-dirs: src
  when:
  - condition: (flag(run-full-suite))
    then:
      cpp-options: -DRUN_FULL_SUITE
    else: {}

Create custom flags in Haskell

1 Answers1