Add CI and cache

.github/workflows/ci.yml

@@ -0,0 +1,64 @@
+name: CI
+
+on:
+  push:
+    branches: ["main"]
+  pull_request:
+    branches: ["main"]
+
+jobs:
+  checks:
+    runs-on: ubuntu-latest
+    steps:
+      - name: checkout
+        uses: actions/checkout@v4
+
+      - name: Install Nix
+        uses: cachix/install-nix-action@v24
+
+      - name: Nix Format Check
+        run: nix fmt -- . --check
+
+      - name: Nix Syntax Check
+        run: nix flake check
+
+  build-plan:
+    # Save some computation. If the checks fail, don't build.
+    needs: checks
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.set-matrix.outputs.matrix }}
+    steps:
+      - name: checkout
+        uses: actions/checkout@v4
+
+      - name: Install Nix
+        uses: cachix/install-nix-action@v24
+
+      - name: Generate Build Matrix
+        id: set-matrix
+        run: |
+          matrix="$(nix eval --json .#githubActions.matrix)"
+          echo "matrix=$matrix" >> $GITHUB_OUTPUT
+
+  build:
+    needs: build-plan
+    runs-on: ${{ matrix.os }}
+    strategy:
+      matrix: ${{fromJSON(needs.build-plan.outputs.matrix)}}
+    steps:
+      - name: checkout
+        uses: actions/checkout@v4
+
+      - name: Install Nix
+        uses: cachix/install-nix-action@v24
+
+      - name: Setup Cache
+        uses: ryanccn/attic-action@f75ac4b827cc5ce58fbf5d56a958db7aee78879c
+        with:
+          endpoint: https://hercules.servers.lowrisc.org/nix-cache/
+          cache: public
+          token: ${{ secrets.NIX_CACHE_TOKEN }}
+
+      - name: Build ${{ matrix.attr }}
+        run: nix build ".#{{ matrix.attr }}"

flake.nix

@@ -5,6 +5,7 @@
   inputs = {
     nixpkgs.url = "github:NixOS/nixpkgs/nixos-23.11";
     flake-utils.url = "github:numtide/flake-utils";
+    nix-github-actions.url = "github:nix-community/nix-github-actions";
 
     poetry2nix = {
       url = "github:nix-community/poetry2nix";
@@ -20,6 +21,7 @@
   } @ inputs: let
     no_system_outputs = {
       lib.poetryOverrides = import ./lib/poetryOverrides.nix;
+      githubActions = inputs.nix-github-actions.lib.mkGithubMatrix {checks = nixpkgs.lib.getAttrs ["x86_64-linux"] self.packages;};
     };
 
     all_system_outputs = flake-utils.lib.eachDefaultSystem (system: let