niv VS ghcid

Sometimes, nixpkgs does not have the Haskell package version I need. In this case, I override the package with a custom one in the Haskell package set. I use niv to pin the version of the package I want to use. If I want to add it from GitHub, that is easy:

niv

Flakes work. An alternative is niv which was once popular and provides a good developer experience.

Essentially you can just think of it as a standardized default.nix/shell.nix with built-in Niv integration.

I agree that the FP part is not the only issue. It's that the community feels a bit more academic/I'll fix this for myself in the way that works best for me.

You can indeed achieve some reproducibility with Docker. It's tricky though, as you'd have to pin exact package versions of software. If you'd `FROM ubuntu:$VERION`, and would run an `apt-get update`, you're not guaranteed to get the same software.

Nix is like ZFS, as that it breaks the wall between two previously distinct area's. Those being building software, and installing/configuration software on your OS. It's quite different from the snapshot-everything methodology that Docker uses. Yeah, one can split in multi-stage images etc, but than you'll be keeping track of which dependencies need to be moved between the stages yourself, in a manner that cannot be abstracted away, so you're doomed to repeat the same patterns over and over again.

People also state that LVM + ext3 is more than sufficient compared to the complexity of ZFS. They miss out on the fact on how much more fine grained solutions are possible with ZFS.

I've used niv [0] before flakes arrived, and am actually still using that instead of flakes. The experimental nature of them has scared me away from them, as I'm not daily involved in this ecosystem at the moment.

[0] https://github.com/nmattia/niv#niv

You can use something like Niv to manage additional sources. I use it to fetch some Emacs packages, for example ligature.el. Then you update the package using $ niv update.

One thing that made this easier was switching from using Nix channels to explicitly pinning my dependencies with Niv. I honestly never fully understood how channels worked, and it's just much nicer to have everything specified in my Git repo. The exact commit of Nixpkgs that I'm using is in my sources.json file, so "reverting" just means checking out an older commit of my configs from Git then running nixos-rebuild switch. If I were redoing my dotfiles today I'd probably use Nix Flakes rather than Niv, but I suspect that Niv is still an easier option to get started with.

Does someone know of a way to remove unused pinned packages via [niv](https://github.com/nmattia/niv)?

Pin nixpkgs, and version control it. If you're using flakes, then just version control the flake.lock alongside your configuration. If you're not using flakes, you can use niv to easily pin nipxkgs, at the expense of some boiler plate.

You can use ghcid. It compiles the code, and shows if there are any errors as you save your file. Have two terminals. One for editing your file...other one with ghcid ($ ghcid path/to/filename.hs). Right click on the ghcid terminal and click `always on top`. That way, It will be always visible as you are typing and saving code.

With a combination of ghcid, an hiedb filewatcher and the -fdefer-type-errors flag you can get pretty solid IDE behavior. Currently only ghc 9.4.4 is supported but happy to personally help people set this up if interested!

With an editor integration, you could rig it up to where you could right-click on a Spec, choose "Run spec" from a context menu, and have your editor add that comment to and save dev.hs. Another editor integration could read and parse the contents of ghcid.txt. We have this already for the compiler output, but it doesn't yet parse the test output. But sans an editor integration, you will still see the test output in the console where Ghcid is running.

Sounds like you want ghcid. You can use it run tests on a successful build, and it will watch files in your project and quick-rebuild when there are changes. There shouldn't be any need to modify your Cabal files or test dependencies.

In addition, for Haskell, I usually have ghcid running, which likewise re-runs on every file change, but gives faster feedback about any type errors than the full compiler, and also is configured to evaluate

Have you looked into ghcid? https://github.com/ndmitchell/ghcid

VS Code + Haskell extension is usually best, but ghcid is an alternative which is much simpler, easier to set up, less pretty and powerful but still pretty easy and effective to use. Here's a workflow:

In general, though, I recommend just looking at the cabal files for various libraries and executables. Something like ghcid is good, since it contains a library, an executable, and a test suite.

you should also checkout the ghci vim plugin https://github.com/ndmitchell/ghcid/tree/master/plugins/nvim