Add haskell-simple-package

haskell-simple-package/Main.hs

@@ -0,0 +1,8 @@
+module Main where
+
+import HaskellSay (haskellSay)
+import ExampleLibrary
+
+main :: IO ()
+main = haskellSay $ "If inverted, False is " ++ writeBool (invert False)
+

haskell-simple-package/README.md

@@ -0,0 +1,16 @@
+## Nix flake for an example haskell package
+
+### To get started:
+- In the `package.yaml`, set any names beginning with `example` to your chosen name - for example, change the `name` setting on the first line from `example-package` to the nameof your new package.
+- Run `hpack` from the terminal; this will generate a cabal file for your project.
+- Run `cabal test` or `cabal run ${executable-name}`, where `${executable-name}` is the name of your executable, defined under `executables` in the `package.yaml`.
+
+### Overview of what's here
+This flake has a simple executable, a library that that executable depends on, and a test suite which tests the library.
+
+It uses cabal to build, hpack as the format for the cabal project specification, and hspec to run tests.
+
+Remember to run `hpack` after any changes to the `package.yaml`, in order to re-create the `${project-name}.cabal` file, as well as the first time you try to use this.
+
+The executable can be run via cabal using `cabal run example-executable`, whereas tests can be run via `cabal test`.
+

haskell-simple-package/flake.nix

@@ -0,0 +1,36 @@
+{
+  description = "Example haskell package with library, executable and tests";
+  inputs = {
+    nixpkgs.url = "nixpkgs";
+    flake-utils.url = github:numtide/flake-utils;
+  };
+  outputs = { self, nixpkgs, flake-utils }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        overlay = (final: prev: {
+          inherit example-package;
+        });
+        pkgs = import nixpkgs {
+          inherit system;
+          overlays = [ overlay ];
+        };
+        example-package = pkgs.haskellPackages.callCabal2nix "example-package" ./. {};
+      in
+      {
+        packages = { inherit example-package; };
+        defaultPackage = example-package;
+        devShell = pkgs.haskellPackages.shellFor {
+            name = "example-package";
+            packages = p: [ example-package ];
+            withHoogle = true;
+            buildInputs = with pkgs; with pkgs.haskellPackages; [
+              haskell-language-server
+              ghcid
+              cabal-install
+              hpack
+            ];
+          shellHook = "command -v fish &> /dev/null && fish";
+          };
+       }
+    );
+}

haskell-simple-package/package.yaml

@@ -0,0 +1,26 @@
+name: example-package
+
+dependencies:
+  - base == 4.*
+  - haskell-say
+
+library:
+  source-dirs: src
+  exposed-modules: ExampleLibrary
+
+executables:
+  example-executable:
+    main: Main.hs
+    dependencies:
+      - example-package
+
+tests:
+  spec:
+    main: Spec.hs
+    source-dirs:
+      - test
+      - src
+    dependencies:
+      - hspec == 2.*
+      - HUnit >= 1.6.0.0
+    build-tools: hspec-discover

haskell-simple-package/src/ExampleLibrary.hs

@@ -0,0 +1,9 @@
+module ExampleLibrary where
+
+invert :: Bool -> Bool
+invert True = False
+invert False = True
+
+writeBool :: Bool -> String
+writeBool True = "True"
+writeBool False = "False"

haskell-simple-package/test/Spec.hs

@@ -0,0 +1,9 @@
+import Test.Hspec
+import ExampleLibrary(invert)
+
+main :: IO ()
+main = hspec $ do
+    describe "test simple functions" $ do
+        it "ensures invert True is False" $ do
+            invert True `shouldBe` False
+