From ebfd17b76a9a51b59217bce399138aaa1e85a603 Mon Sep 17 00:00:00 2001
From: Brian McGee <brian@bmcgee.ie>
Date: Wed, 8 May 2024 08:54:58 +0100
Subject: [PATCH] feat: add nix github workflow

Signed-off-by: Brian McGee <brian@bmcgee.ie>
---
 .github/workflows/nix.yml | 36 ++++++++++++++++++++++++++++++++
 flake.lock                | 43 ++++++++++++++++++++++-----------------
 flake.nix                 | 11 ++++++++--
 nix/checks.nix            | 13 +++++++++++-
 4 files changed, 81 insertions(+), 22 deletions(-)
 create mode 100644 .github/workflows/nix.yml

diff --git a/.github/workflows/nix.yml b/.github/workflows/nix.yml
new file mode 100644
index 0000000..d6ff466
--- /dev/null
+++ b/.github/workflows/nix.yml
@@ -0,0 +1,36 @@
+name: Nix Flake Actions
+on:
+    push:
+        branches:
+            - main
+    pull_request:
+    workflow_dispatch:
+
+jobs:
+    nix-matrix:
+        runs-on: ubuntu-latest
+        outputs:
+            matrix: ${{ steps.set-matrix.outputs.matrix }}
+        steps:
+            - uses: actions/checkout@v4
+            - uses: cachix/install-nix-action@v26
+            - id: set-matrix
+              name: Generate Nix Matrix
+              run: |
+                  set -Eeu
+                  matrix="$(nix eval --json '.#githubActions.matrix')"
+                  echo "matrix=$matrix" >> "$GITHUB_OUTPUT"
+
+    nix-build:
+        needs: nix-matrix
+        runs-on: ${{ matrix.os }}
+        strategy:
+            matrix: ${{fromJSON(needs.nix-matrix.outputs.matrix)}}
+        steps:
+            - uses: actions/checkout@v4
+            - uses: cachix/install-nix-action@v26
+            - uses: cachix/cachix-action@v14
+              with:
+                  name: numtide
+                  authToken: "${{ secrets.CACHIX_AUTH_TOKEN }}"
+            - run: nix build -L ".#${{ matrix.attr }}"
diff --git a/flake.lock b/flake.lock
index 34c5d62..1528488 100644
--- a/flake.lock
+++ b/flake.lock
@@ -38,7 +38,9 @@
     },
     "flake-parts": {
       "inputs": {
-        "nixpkgs-lib": "nixpkgs-lib"
+        "nixpkgs-lib": [
+          "nixpkgs"
+        ]
       },
       "locked": {
         "lastModified": 1712014858,
@@ -111,6 +113,26 @@
         "type": "github"
       }
     },
+    "nix-github-actions": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1703863825,
+        "narHash": "sha256-rXwqjtwiGKJheXB43ybM8NwWB8rO2dSRrEqes0S7F5Y=",
+        "owner": "nix-community",
+        "repo": "nix-github-actions",
+        "rev": "5163432afc817cf8bd1f031418d1869e4c9d5547",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "nix-github-actions",
+        "type": "github"
+      }
+    },
     "nixpkgs": {
       "locked": {
         "lastModified": 1714253743,
@@ -127,24 +149,6 @@
         "type": "github"
       }
     },
-    "nixpkgs-lib": {
-      "locked": {
-        "dir": "lib",
-        "lastModified": 1711703276,
-        "narHash": "sha256-iMUFArF0WCatKK6RzfUJknjem0H9m4KgorO/p3Dopkk=",
-        "owner": "NixOS",
-        "repo": "nixpkgs",
-        "rev": "d8fe5e6c92d0d190646fb9f1056741a229980089",
-        "type": "github"
-      },
-      "original": {
-        "dir": "lib",
-        "owner": "NixOS",
-        "ref": "nixos-unstable",
-        "repo": "nixpkgs",
-        "type": "github"
-      }
-    },
     "root": {
       "inputs": {
         "devshell": "devshell",
@@ -152,6 +156,7 @@
         "flake-parts": "flake-parts",
         "gomod2nix": "gomod2nix",
         "nix-filter": "nix-filter",
+        "nix-github-actions": "nix-github-actions",
         "nixpkgs": "nixpkgs",
         "treefmt-nix": "treefmt-nix"
       }
diff --git a/flake.nix b/flake.nix
index 8fafef7..35a89b3 100644
--- a/flake.nix
+++ b/flake.nix
@@ -3,7 +3,10 @@
 
   inputs = {
     nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
-    flake-parts.url = "github:hercules-ci/flake-parts";
+    flake-parts = {
+      url = "github:hercules-ci/flake-parts";
+      inputs.nixpkgs-lib.follows = "nixpkgs";
+    };
     treefmt-nix = {
       # todo switch back to numtide/treefmt-nix once merged
       url = "github:brianmcgee/treefmt-nix/feat/pipelines";
@@ -16,10 +19,14 @@
     gomod2nix = {
       url = "github:nix-community/gomod2nix";
       inputs.nixpkgs.follows = "nixpkgs";
-      inputs.flake-utils.follows ="devshell/flake-utils";
+      inputs.flake-utils.follows = "devshell/flake-utils";
     };
     nix-filter.url = "github:numtide/nix-filter";
     flake-compat.url = "github:nix-community/flake-compat";
+    nix-github-actions = {
+      url = "github:nix-community/nix-github-actions";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
   };
 
   outputs = inputs @ {flake-parts, ...}:
diff --git a/nix/checks.nix b/nix/checks.nix
index 8216515..500f224 100644
--- a/nix/checks.nix
+++ b/nix/checks.nix
@@ -1,5 +1,16 @@
-{lib, ...}: {
+{
+  lib,
+  inputs,
+  self,
+  ...
+}: {
+  # generate github actions matrix using the flake's checks
+  flake.githubActions = inputs.nix-github-actions.lib.mkGithubMatrix {
+    checks = lib.getAttrs ["x86_64-linux" "x86_64-darwin"] self.checks;
+  };
+
   perSystem = {self', ...}: {
+    # mixin every package
     checks = with lib; mapAttrs' (n: nameValuePair "package-${n}") self'.packages;
   };
 }