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# haskell-template
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Haskell project template optimized for a fully reproducible and friendly development environment. Based on:
- [Nix ](http://www.srid.ca/haskell-nix ) + [Flakes ](https://serokell.io/blog/practical-nix-flakes ) + GHC 9
- VSCode + [HLS ](https://github.com/haskell/haskell-language-server )
- [fourmolu ](https://github.com/fourmolu/fourmolu ) autoformatting
- [Relude ](https://github.com/kowainik/relude#relude ) as Prelude.
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- `.hlint.yaml` is [from relude ](https://github.com/kowainik/relude/blob/main/.hlint.yaml )
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## Getting Started
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First-time setup:
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- [Install Nix ](https://nixos.org/download.html ) & [enable Flakes ](https://nixos.wiki/wiki/Flakes )
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- Run `nix develop -c haskell-language-server` to sanity check your environment
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- [Open as single-folder workspace ](https://code.visualstudio.com/docs/editor/workspaces#_singlefolder-workspaces ) in Visual Studio Code
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- When prompted by VSCode, install the [workspace recommended ](https://code.visualstudio.com/docs/editor/extension-marketplace#_workspace-recommended-extensions ) extensions
- < kbd > Ctrl+Shift+P</ kbd > to run command "Nix-Env: Select Environment" and then select `shell.nix` .
- The extension will ask you to reload VSCode at the end. Do it.
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To run the program with auto-recompile:
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- Press < kbd > Ctrl+Shift+B</ kbd > in VSCode, or run `bin/run` in terminal, to launch Ghcid running your program.
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Open `Main.hs` , and expect all HLS IDE features like hover-over tooltip to work out of the box. Try changing the source, and expect Ghcid to re-compile and re-run the app in the terminal below.
---
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Renaming the project:
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```sh
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git clone < your-clone-url >
cd your-project
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NAME=myproject
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git mv haskell-template.cabal ${NAME}.cabal
nix run nixpkgs#sd -- haskell-template ${NAME} * * /*
git add . & & git commit -m rename
```
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## Tips
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- Run `nix flake update` to update all flake inputs.
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- Run `treefmt` in nix shell to autoformat the project. This uses [treefmt ](https://github.com/numtide/treefmt ), which uses `./treefmt.toml` (where fourmolu and nixpkgs-fmt are specified).
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## Alternatives
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- haskell.nix: [Getting started with Flakes ](https://input-output-hk.github.io/haskell.nix/tutorials/getting-started-flakes.html )
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- [Serokell's Flake template ](https://github.com/serokell/templates/tree/master/haskell-cabal2nix )
- [Same, but using haskell.nix ](https://github.com/serokell/templates/pull/2 )
