replace shell.nix with Nix Flake (#1154)

* `flake.nix`

Squashed commit of the following:

commit fae5c89
Author: Peter Becich <peterbecich@gmail.com>
Date:   Sun Mar 12 21:43:23 2023 -0700

    `nix develop` and `nix build` work

commit 9c3d54e
Author: Peter Becich <peterbecich@gmail.com>
Date:   Sun Mar 5 13:24:29 2023 -0800

    use https://github.com/srid/haskell-flake

commit a56bcee
Author: Peter Becich <peterbecich@gmail.com>
Date:   Fri Mar 3 22:21:27 2023 -0800

    update sources

commit b013302
Author: Peter Becich <peterbecich@gmail.com>
Date:   Tue Feb 28 18:06:28 2023 -0800

    update Cabal in both NixPkgs and hackage.nix

commit aaff29c
Author: Peter Becich <peterbecich@gmail.com>
Date:   Mon Feb 27 18:55:48 2023 -0800

    attempt to fix `doctest-parallel` by updating Cabal

    input-output-hk/haskell.nix#1829

commit ccc9ced
Author: Peter Becich <peterbecich@gmail.com>
Date:   Sun Feb 26 23:16:28 2023 -0800

    investigate `gd` build error in `nix develop` shell

    input-output-hk/haskell.nix#1865

commit efd9de5
Author: Peter Becich <peterbecich@gmail.com>
Date:   Sun Feb 26 01:49:08 2023 -0800

    more dependencies

commit fb94055
Author: Peter Becich <peterbecich@gmail.com>
Date:   Sun Feb 26 01:19:33 2023 -0800

    work on `develop` shell

commit 495a54e
Author: Peter Becich <peterbecich@gmail.com>
Date:   Sat Feb 4 16:28:05 2023 -0800

    replace `shell.nix` with `haskell.nix` Flake

commit e0e8f41
Author: Peter Becich <peterbecich@gmail.com>
Date:   Sun Feb 5 17:56:04 2023 -0800

    ignore `incomplete-uni-patterns` warning

commit e4747e9
Author: Peter Becich <peterbecich@gmail.com>
Date:   Sat Feb 4 15:31:06 2023 -0800

    fix `incomplete-uni-patterns` warning, ignore some others

    the `flake.nix` build fails on these warnings: #1154

* Mac support in `flake.nix`

* disable `nix flake check` in CI

Author: peterbecich

.envrc

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

.github/workflows/nix-shell.yml.off renamed to .github/workflows/nix-flake.yml

@@ -1,21 +1,25 @@
-name: "Test nix-shell"
+name: "Test Nix Flake"
 on:
   push:
     branches:
       - master
-      - ci*
   pull_request:
     branches:
       - master
-      - ci*
 jobs:
-  nix-shell:
-    runs-on: ubuntu-latest
+  nix:
+    strategy:
+      fail-fast: true
+      matrix:
+        os:
+        - ubuntu-latest
+        - macos-latest
+    name: Nix on ${{ matrix.os }}
+    runs-on: ${{ matrix.os }}
     steps:
     - uses: actions/checkout@v3.1.0
-    - uses: cachix/install-nix-action@v18
+    - uses: cachix/install-nix-action@v20
       with:
-        nix_path: nixpkgs=channel:nixos-21.11
         extra_nix_config: |
           trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= hackage-server.cachix.org-1:iw0iRh6+gsFIrxROFaAt5gKNgIHejKjIfyRdbpPYevY=
           substituters = https://hydra.iohk.io https://cache.nixos.org/ https://hackage-server.cachix.org/
@@ -24,4 +28,5 @@ jobs:
         # https://nix.dev/tutorials/continuous-integration-github-actions#setting-up-github-actions
         name: hackage-server
         authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
-    - run: nix-shell --pure --run ./.github/workflows/test-nix-shell.sh
+    - run: nix build
+    # - run: nix flake check

.github/workflows/test-nix-shell.sh

@@ -15,3 +15,6 @@ tags
 *.swp
 TAGS
 *~
+.direnv
+
+result*

.gitignore

@@ -2,25 +2,32 @@
 
 [![Build Status](https://travis-ci.org/haskell/hackage-server.png?branch=master)](https://travis-ci.org/haskell/hackage-server)
 [![Build status](https://github.com/haskell/hackage-server/actions/workflows/haskell-ci.yml/badge.svg)](https://github.com/haskell/hackage-server/actions/workflows/haskell-ci.yml)
-[![Build status](https://github.com/haskell/hackage-server/actions/workflows/nix-shell.yml/badge.svg)](https://github.com/haskell/hackage-server/actions/workflows/nix-shell.yml)
+[![Build status](https://github.com/haskell/hackage-server/actions/workflows/nix-flake.yml/badge.svg)](https://github.com/haskell/hackage-server/actions/workflows/nix-flake.yml)
 
 This is the `hackage-server` code. This is what powers <http://hackage.haskell.org>, and many other private hackage instances. The `master` branch is suitable for general usage. Specific policy and documentation for the central hackage instance exists in the `central-server` branch.
 
 ## Installing dependencies
 
 `hackage-server` depends on `libgd` and `zlib`. You'll also need `libbrotli-dev` for enabling tests.
 
-### [`nix-shell`](https://nixos.org/manual/nix/stable/command-ref/nix-shell.html)
+### [`nix develop`](https://nixos.org/manual/nix/stable/command-ref/new-cli/nix3-develop.html)
 
-If you have the [Nix package manager](https://nixos.org/) installed, the easiest way to run `hackage-server` is by using the `nix-shell`. It should be unnecessary to install any dependencies manually. In this repository:
+If you have the [Nix package manager](https://nixos.org/) installed, the easiest way to run `hackage-server` is by using `nix develop`. It should be unnecessary to install any dependencies manually. In this repository:
 
-    nix-shell --pure
+    nix develop
 
-    [nix-shell]$ cabal v2-run -- hackage-server init
+    (in develop shell)
+    $ cabal v2-run -- hackage-server init
 
-    [nix-shell]$ cabal v2-run -- hackage-server run --static-dir=datafiles/ --base-uri=http://127.0.0.1:8080
+    $ cabal v2-run -- hackage-server run --static-dir=datafiles/ --base-uri=http://127.0.0.1:8080
     hackage-server: Ready! Point your browser at http://127.0.0.1:8080
 
+`flake.nix` is provided; it uses [`srid/haskell-flake`](https://github.com/srid/haskell-flake).
+
+If you have [direnv](https://direnv.net/), `direnv allow` will load this `nix develop` shell automatically.
+
+`nix build` will build a `hackage-server` executable in `result/`. The Hackage dependencies are provided by the inputs specified in `flake.nix`. Because some of these inputs are unpublished commits on GitHub, this build should not be considered authoritative.
+
 ### Manually
 
 You can also install dependencies manually via your operating system's package

README.md

@@ -8,7 +8,6 @@
 
 packages: .
 
-
 allow-newer: rss:time, rss:base
 
 -- Andreas, 2022-10-28:  `Cabal-3.8.1.0` wants `process >= 1.6.14`