Flags in cabal files

Question

I am following the user-guide for package developing: https://www.haskell.org/cabal/users-guide/developing-packages.html#quickstart

I got stuck in the Flags

Answer 1

Pass the flags to cabal configure, e.g.:

cabal configure -f debug

Answer 2

With Stack, use

stack build --flag <pkg>:debug

to set debug flag to True for <pkg>, or use --flag '*:debug' to set debug flag to True for all packages. Replace debug with -debug to set debug flag to False.

You can also specify flag settings in a stack.yaml file. For example, to set debug flag to False for <pkg>, add this to your stack.yaml:

flags:
  <pkg>:
    debug: false

Answer 3

With cabal-2.1.0 you can do it like this:

cabal new-build -f debug