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Why cabal sandbox init does not change PATH like virtualenv does?

Haskell newbie and Python guy here.

I think I may be missing something here but if you look at Yesod's quickstart, the autor install some packages before cabal sandbox init. I have seen the same pattern elsewhere. Questions:

  1. Am I missing something? Is this the real way to use cabal sandbox?
  2. Why can't (or shouldn't) I install yesod-bin inside a sandbox?
  3. What if I use different versions of yesod-bin throughout some projects?
  4. If there is some libraries that install binaries inside .cabal-sandbox/bin, why cabal sandbox init don't change PATH in order to match the sandboxed version?

Thank you very much in advance!

Solution

    1. Yes, this how to use a sandbox.

      cabal sandbox init will create some files / directories for you that will keep track of the packages you have installed.

      cabal install some_package will install that package into the sandbox.

    2. You are more than welcome to install yesod-bin into a sandbox.

    3. Read point 2

    4. cabal sandbox init doesn't change your path, because it doesn't really need to. Just add PATH=.cabal-sandbox/bin:$PATH in your .bash_profile.

      Unlike virtual-env, you never need to 'enable' or 'disable' a sandbox. You just cd into a directory, and it is automatically enabled.

      The only real downside I have found to cabal sandboxes, is that you need to be in the root directory in order to act upon a sandbox. Meaning, if you are in a sub-directory, running cabal install some_package will not install it into the sandbox that is up a level, instead it will install it into either the global or user database, depending on how you have cabal configured.