Cabal 2.0 operations fail without an internet connection with default settings.

[dalaing]

I updated my NixOS VM last night, which bumped my cabal versions to:

> cabal --version
cabal-install version 2.0.0.0
compiled using version 2.0.0.2 of the Cabal library

and then tried to do some development on my train trip into work:

> cabal build
Warning: Caught exception during _mirrors lookup:dieVerbatim: user error
(cabal: '/run/current-system/sw/bin/nslookup' exited with an error:
)
Warning: No mirrors found for http://hackage.haskell.org/
dieVerbatim: user error (cabal: '/run/current-system/sw/bin/curl' exited with an error:
curl: (6) Could not resolve host: hackage.haskell.org

I can comment out the repository information in ~/.cabal/config as a temporary workaround, but it seems like a bad user experience that could be fixed.

[schmittlauch]

I, another Nix user, am affected by this as well. Particularly I have set up an isolated nixos container with an environment of all required Haskell dependencies already fetched at container-build time, thanks to cabal2nix. At runtime, cabal run is invoked only within that nix-shell environment with all dependencies being locally available. The container has no internet access and thus cannot reach the hackage indexing servers.

Emptying the cabal config is a workaround, but please keep this use case in mind.

[phadej]

Use active-repositories: :none in cabal.project (with cabal-install: 3.4).