snapframework/snap

-fdevelopment Snap servers can hang with GHC warnings switched on

Opened this issue · 4 comments

JulianBirch commented

Hi, apologies if this isn't the right place to log this. It's pretty easy to reproduce:

  • create a new project using snap init
  • add {-# OPTIONS_GHC -Wall #-} to Site.hs
  • cabal install -fdevelopment
  • run the project

Project compiles fine, then proceeds to hang when you access the first page, printing the warning out on the console.

Having tracked down the cause, I don't know if it's even solvable...

(Updated: initial report was a lot more complex)

chowells79 commented

This isn't solvable so long as we're using hint to do the interpreting. It can't handle code that compiles successfully with warnings.

chowells79 commented

Though hanging is odd behavior. I'm not sure why it'd do that.

mightybyte commented

Could it be a bug in GHC or hint?

JulianBirch commented

This is probably just my inexperience talking, but I really don't understand the behaviour. For instance, my reading of the cabal file says that Wall is switched on, but if I run cabal install I don't get any warnings. So, even if I did cabal install && cabal install -fdevelopment I'd run into the problem.

Edit: I discovered this: http://stackoverflow.com/questions/12273315/how-to-recompile-haskell-with-cabal-build-showing-only-warnings