at HEAD: `cabal build` fails in `nix develop` environment, failing to build `ekg-json`: `unordered-containers` unknown

[cxandru]

I'm trying to start contributing to hls and have run into the above error. More details below:

Your environment

Which OS do you use?
NixOS, nix develop at git HEAD

What's wrong?

HEAD is now at 7a0af7a compat with aeson 2.x and relax upper bounds
Warning: No remote package servers have been specified. Usually you would have
one specified in the config file.
Resolving dependencies...
Error: cabal: Could not resolve dependencies:
[__0] trying: ekg-json-0.1.0.7 (user goal)
[__1] unknown package: unordered-containers (dependency of ekg-json)
[__1] fail (backjumping, conflict set: ekg-json, unordered-containers)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: ekg-json, unordered-containers

[cxandru]

nix build on the other hand works just fine.

[cxandru]

At https://haskell-language-server.readthedocs.io/en/latest/contributing/contributing.html#using-nix it says to do the following steps:

$ cachix use haskell-language-server
$ nix-shell
$ cabal update
$ cabal build

Is cabal update then supposed to output something other than 'No remote repositories configured'?

[michaelpj]

cc @guibou

[michaelpj]

Hopefully stale.