chore: init

templates/haskell/.envrc

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+use flake

templates/haskell/.gitignore

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+.direnv
+.pre-commit-config.yaml
+.vscode
+dist-newstyle

templates/haskell/flake.nix

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+{
+  description = "Haskell Environment";
+
+  inputs = {
+    flake-parts.url = "github:hercules-ci/flake-parts";
+    nixpkgs.url = "github:NixOS/nixpkgs/nixos-unstable";
+    treefmt-nix.url = "github:numtide/treefmt-nix";
+  };
+
+  outputs =
+    inputs:
+    inputs.flake-parts.lib.mkFlake { inherit inputs; } {
+      imports = [ inputs.treefmt-nix.flakeModule ];
+
+      perSystem =
+        { pkgs, ... }:
+        let
+          hp = pkgs.haskellPackages;
+          project = hp.callCabal2nix "project" ./. { };
+        in
+        {
+          devShells.default = hp.shellFor {
+            nativeBuildInputs = builtins.attrValues {
+              inherit (pkgs)
+                nil
+                stylish-haskell
+                ghc
+                ;
+              inherit (hp)
+                cabal-install
+                cabal-gild
+                haskell-language-server
+                ;
+            };
+            packages = _: [ project ];
+          };
+
+          packages.default = project;
+
+          treefmt = {
+            programs = {
+              cabal-fmt.enable = true;
+              deadnix.enable = true;
+              hlint.enable = true;
+              nixfmt.enable = true;
+              ormolu.enable = true;
+              statix.enable = true;
+              typstyle.enable = true;
+              yamlfmt.enable = true;
+            };
+            projectRootFile = "flake.nix";
+          };
+        };
+
+      systems = [ "x86_64-linux" ];
+    };
+}

templates/haskell/fourmolu.yaml

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+indentation: 2
+comma-style: trailing
+import-export-style: diff-friendly
+respectful: false
+column-limit: 80
+function-arrows: trailing
+haddock-style: single-line
+let-style: inline
+in-style: right-align
+unicode: never
+pragma-style: leading
+newlines-between-decls: 1

templates/haskell/justfile

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+cabal:
+    cabal clean ; cabal run

templates/haskell/project.cabal

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+cabal-version: 3.0
+name:          project
+version:       0.1.0.0
+
+executable main
+  main-is:          Main.hs
+  build-depends:
+    , base
+  default-language: Haskell2010
+  hs-source-dirs:   src

templates/haskell/src/Main.hs

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+module Main where
+
+main :: IO ()
+main = putStrLn "Hello, World!"