Oddity with cabal, HTF and HUnit statements

Question

So I'm trying to use HTF to run some statements like HUnit

% cat tests/TestDemo.hs
{-# OPTIONS_GHC -Wall -F -pgmF htfpp #-}
module Main where
import Test.Framework
import Test.HUnit.Base ((@?=))
import System.Environment (getArgs)

-- just run some tests
main :: IO ()
main = getArgs >>= flip runTestWithArgs Main.allHTFTests

-- all these tests should fail
test_fail_int1 :: Assertion
test_fail_int1 = (0::Int) @?= (1::Int)

test_fail_bool1 :: Assertion
test_fail_bool1 = True @?= False

test_fail_string1 :: Assertion
test_fail_string1 = "0" @?= "1"

test_fail_int2 :: Assertion
test_fail_int2 = [0::Int] @?= [1::Int]

test_fail_string2 :: Assertion
test_fail_string2 = "true" @?= "false"

test_fail_bool2 :: Assertion
test_fail_bool2 = [True] @?= [False]

And when I use ghc --make, it works correctly.

% ghc --make tests/TestDemo.hs
[1 of 1] Compiling Main             ( tests/TestDemo.hs, tests/TestDemo.o )
Linking tests/TestDemo ...
% tests/TestDemoA
...
* Tests:    6
* Passed:   0
* Failures: 6
* Errors:   0

Failures:
  * Main:fail_int1 (tests/TestDemo.hs:9)
  * Main:fail_bool1 (tests/TestDemo.hs:12)
  * Main:fail_string1 (tests/TestDemo.hs:15)
  * Main:fail_int2 (tests/TestDemo.hs:19)
  * Main:fail_string2 (tests/TestDemo.hs:22)
  * Main:fail_bool2 (tests/TestDemo.hs:25)

But when I use cabal to build it, not all tests that should fail will fail.

% cat Demo.cabal
...
executable test-demo
  build-depends: base >= 4, HUnit, HTF
  main-is: TestDemo.hs
  hs-source-dirs: tests
% cabal configure
Resolving dependencies...
Configuring Demo-0.0.0...
% cabal build
Preprocessing executables for Demo-0.0.0...
Building Demo-0.0.0...
[1 of 1] Compiling Main             ( tests/TestDemo.hs, dist/build/test-demo/test-demo-tmp/Main.o )
Linking dist/build/test-demo/test-demo ...
% dist/build/test-demo/test-demo
...
* Tests:    6
* Passed:   3
* Failures: 3
* Errors:   0

Failures:
  * Main:fail_int2 (tests/TestDemo.hs:23)
  * Main:fail_string2 (tests/TestDemo.hs:26)
  * Main:fail_bool2 (tests/TestDemo.hs:29)

What is going wrong and how can I fix it?

Answer 1

This is a bug in some versions of GHC related to the optimizer that removes IO exceptions in some cases. This is very common with HUnit code if optimization is enabled. And enslaving sets -O1by default, which allows you to get an error.

GHC 7 ( , , IE haskell GHC 7).

-O0 .cabal, . , , GHC 7.