cabal-version: 2.2
name:          pkg-foo
version:       0

flag foo-bar
  description: Should be toggled
  manual:      False
  default:     False

library
  default-language: Haskell2010
  build-depends:    base
  exposed-modules:  Foo

  -- this says "toggle me"
  if !flag(foo-bar)
    build-depends: base <0