How can environment file get into invalid state?

[tomjaguarpaw]

A user was having trouble with cabal and posted his environment file to haskell-cafe. It contains entries for ghc-8.4.4 and directory-1.3.7.1, which are mutually incompatible. Therefore cabal stopped working. I assume the environment file got into this state just through running cabal install and/or cabal install --lib rather than manually editing the environment file or using any other tooling. That's what the thread suggests at least.

If it did get this way through cabal, how is that possible? Can cabal really create an environment file with mutually incompatible packages in it?

[Mikolaj]

The user clearly states "cabal install --lib" has been involved.

[tomjaguarpaw]

Yes. Can cabal install --lib get the environment file into an invalid state?

[volkerwysk]

Hi! That user, that's me. Yes, I've just run cabal install and cabal install --lib. I haven't touched that environment file, or done any other tooling.

[ulysses4ever]

@tomjaguarpaw yes, this is a known problem, unfortunately. See #5559 (and if you're still curious #7373).

[tomjaguarpaw]

Ah thank you! That resolves my question.