replace nix-shell with Nix Flake (#737)

* replace `nix-shell` with Nix Flake

This `flake.nix` provides the same resources as the deleted Nix files with less code to maintain.

This commit does not fix/update the docs generation via Nix; this remains TODO.

* Nix Flake GitHub Action badge

* test Nix Flake on both Mac and Linux

* Apply suggestions from code review

Co-authored-by: Ken Micklas <git@kmicklas.com>

---------

Co-authored-by: Ken Micklas <git@kmicklas.com>

Author: peterbecich

.envrc

@@ -0,0 +1 @@
+use flake

.github/workflows/nix-flake.yaml

@@ -0,0 +1,24 @@
+name: "Nix Flake"
+on:
+  pull_request:
+  push:
+jobs:
+  nix:
+    strategy:
+      fail-fast: true
+      matrix:
+        os:
+        - ubuntu-latest
+        - macos-latest
+    name: Nix on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
+    steps:
+      - uses: actions/checkout@v4
+      - uses: DeterminateSystems/nix-installer-action@main
+      - uses: DeterminateSystems/magic-nix-cache-action@main
+      - name: "Check `nix develop` shell"
+        run: nix develop --check
+      - name: "Check `nix develop` shell can run command"
+        run: nix develop --command "true"
+      - run: nix build
+      - run: nix flake check

.gitignore

@@ -23,3 +23,4 @@ TAGS
 docs/ChinookData
 result
 result-*
+.direnv

README.md

@@ -1,6 +1,7 @@
 # Beam: a type-safe, non-TH Haskell relational database library and ORM
 
 [![Build status](https://github.com/haskell-beam/beam/workflows/Build/badge.svg)](https://github.com/haskell-beam/beam/workflows/Build/badge.svg)
+[![Build status](https://github.com/haskell-beam/beam/actions/workflows/nix-flake.yaml/badge.svg)](https://github.com/haskell-beam/beam/actions/workflows/nix-flake.yaml)
 
 If you use beam commercially, please consider a donation to make this project possible: https://liberapay.com/tathougies
 
@@ -79,12 +80,15 @@ to run this against. See the documentation for examples.
 
 ## Building the documentation
 
-Beam uses `mkdocs` for its documentation generation. The included
-`build-docs.sh` script can take care of building the documentation and serving
-it locally. In order to use the tool though, make sure you have a python
-installation with the `mkdocs` module installed. You can do this by creating a
-virtualenv, and pip installing `mkdocs`, or in a Nix shell with
-`nix-shell docs`.
+Beam uses [`mkdocs`](https://www.mkdocs.org/) for its documentation generation.
+
+### Requirements
+* Python installation with [`mkdocs` module](https://pypi.org/project/mkdocs/)
+* Alternatively, open the Nix Flake shell via `nix develop`.
+
+Then run `build-docs.sh`.
+
+TODO: define Nix package for docs bundle.
 
 The documentation uses a custom Markdown preprocessor to automatically build
 examples against the canonical Chinook database. By default, beam will build

docs/default.nix

@@ -4,8 +4,6 @@
 with nixpkgs;
 
 let
-  beamLib = import ../nix/lib.nix { inherit nixpkgs; };
-  beamGhc = beamLib.makeBeamGhc ghc;
   docsEnv = poetry2nix.mkPoetryEnv {
     projectDir = ./.;
   };
@@ -51,7 +49,7 @@ stdenv.mkDerivation {
     []
     ./..;
   nativeBuildInputs = [
-    (beamGhc.ghc.withPackages beamLib.beamPackageList)
+    # (beamGhc.ghc.withPackages beamLib.beamPackageList)
     docsEnv
     poetry
     postgresql

flake.lock

@@ -0,0 +1,62 @@
+{
+  inputs = {
+    nixpkgs.url = "github:nixos/nixpkgs";
+    flake-parts.url = "github:hercules-ci/flake-parts";
+    haskell-flake.url = "github:srid/haskell-flake";
+
+    testcontainers.url =
+      "github:testcontainers/testcontainers-hs/e286bd2ba9747c2d8c3756a3a89910e579e318e3";
+    testcontainers.flake = false;
+  };
+  outputs = inputs@{ self, nixpkgs, flake-parts, ... }:
+    flake-parts.lib.mkFlake { inherit inputs; } {
+      systems = nixpkgs.lib.systems.flakeExposed;
+      imports = [ inputs.haskell-flake.flakeModule ];
+
+      perSystem = { self', pkgs, ... }: {
+
+        haskellProjects.default = {
+          basePackages = pkgs.haskell.packages.ghc98;
+
+          packages = {
+            testcontainers.source = inputs.testcontainers;
+          };
+          settings = {
+            testcontainers.check = false;
+            beam-postgres.check = false;
+          };
+
+          devShell = {
+           enable = true;
+
+           hlsCheck.enable = false;
+
+           tools = hp: {
+             inherit (pkgs)
+               postgresql
+               sqlite-interactive
+               poetry
+               curl
+               pv # http://www.ivarch.com/programs/pv.shtml
+             ;
+           };
+          };
+        };
+
+        packages.all = pkgs.symlinkJoin {
+          name = "all";
+          paths = [
+            self'.packages.beam-core
+            self'.packages.beam-migrate
+            self'.packages.beam-postgres
+            self'.packages.pagila
+            self'.packages.beam-sqlite
+          ];
+        };
+
+        packages.default = self'.packages.all;
+
+        # docs = import ./docs { inherit nixpkgs; };
+      };
+    };
+}