Test Nix on CI (amber-lang#385)

* Build Nix package on CI

* Resolve duplicate inputs and flake update

* Switch to rust-overlay

* Check that the `bc` command is included and set path works correctly

* Exit if check fails

* Move Nix checks to its own workflow

.github/workflows/nix.yml

@@ -0,0 +1,30 @@
+name: Build verify Amber Nix
+on:
+  push:
+    branches:
+      - master
+  workflow_dispatch:
+
+env:
+  CARGO_TERM_COLOR: always
+
+jobs:
+  nix_build:
+    name: Nix build
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v4
+      - uses: cachix/install-nix-action@v27
+      - name: Check Nix flake
+        run: nix flake check --all-systems
+      - name: Build in Nix shell
+        run: nix develop --command cargo build --release
+      - name: Build with Nix
+        run: |
+          nix build
+
+          # Ensure that the `amber` binary runs
+          ./result/bin/amber --version
+
+          # Ensure that the `bc` command is correctly provided
+          echo "import { exit } from \"std/env\"\n\$which bc && bc --version\$ failed { echo \"Failed to run basic calculator\"\nexit(1) }" | ./result/bin/amber -

.github/workflows/rust.yml

@@ -10,6 +10,8 @@ on:
       - Cargo.toml
       - Cargo.lock
       - rust-toolchain.toml
+      - flake.nix
+      - flake.lock
   pull_request:
     paths:
       - src/**
@@ -18,6 +20,8 @@ on:
       - Cargo.toml
       - Cargo.lock
       - rust-toolchain.toml
+      - flake.nix
+      - flake.lock
 
 env:
   CARGO_TERM_COLOR: always

flake.nix

@@ -1,60 +1,55 @@
 {
   inputs = {
-    naersk.url = "github:nix-community/naersk/master";
-    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+    nixpkgs.url = "github:NixOS/nixpkgs?ref=nixpkgs-unstable";
+
+    naersk = {
+      url = "github:nix-community/naersk?ref=master";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
     utils.url = "github:numtide/flake-utils";
-    nixpkgs-mozilla = {
-      url = "github:mozilla/nixpkgs-mozilla";
-      flake = false;
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs.nixpkgs.follows = "nixpkgs";
     };
   };
 
   outputs =
-    {
-      self,
-      nixpkgs,
-      utils,
-      naersk,
-      nixpkgs-mozilla,
+    { self
+    , nixpkgs
+    , utils
+    , naersk
+    , rust-overlay
+    ,
     }:
     utils.lib.eachDefaultSystem (
       system:
       let
         pkgs = import nixpkgs {
           inherit system;
-          overlays = [ (import nixpkgs-mozilla) ];
+          overlays = [ (import rust-overlay) ];
         };
-        toolchain =
-          (pkgs.rustChannelOf {
-            rustToolchain = ./rust-toolchain.toml;
-            sha256 = "sha256-Ngiz76YP4HTY75GGdH2P+APE/DEIx2R/Dn+BwwOyzZU=";
-          }).rust;
+        toolchain = pkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
         naersk-lib = pkgs.callPackage naersk {
           cargo = toolchain;
           rustc = toolchain;
         };
       in
       {
+        formatter = pkgs.nixpkgs-fmt;
         packages.default = naersk-lib.buildPackage {
           src = ./.;
           nativeBuildInputs = [ pkgs.makeWrapper ];
           postInstall = ''
-            wrapProgram "$out/bin/amber" --set PATH ${nixpkgs.lib.makeBinPath [ pkgs.bc ]}
+            wrapProgram "$out/bin/amber" --prefix PATH : ${nixpkgs.lib.makeBinPath [ pkgs.bc ]}
           '';
         };
         devShells.default =
-          with pkgs;
-          mkShell {
-            buildInputs = [
+          pkgs.mkShell {
+            packages = with pkgs; [
               bc
-              cargo
-              rustc
-              rustfmt
               pre-commit
-              rustPackages.clippy
-            ];
-            nativeBuildInputs = [ toolchain ];
-            RUST_SRC_PATH = rustPlatform.rustLibSrc;
+            ] ++ [ toolchain ];
+            RUST_SRC_PATH = toolchain.availableComponents.rust-src;
           };
       }
     );