Set up a Nix build. (#121)

This ensures the Nix shell uses the same Rust toolchain as `rustup`, and
ensures we can build the package both with and without Nix.

.github/workflows/nix.yaml

@@ -1,8 +1,56 @@
-name: test Nix support
+name: Nix
 
 on: push
 
 jobs:
+  nix-build:
+    name: nix build
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout 🛎️
+        uses: actions/checkout@v3
+
+      - name: Install Nix ❄
+        uses: DeterminateSystems/nix-installer-action@v9
+
+      - name: Run the Magic Nix Cache 🔌
+        uses: DeterminateSystems/magic-nix-cache-action@v3
+
+      - name: Build the package
+        run: nix build
+
+  nix-flake-check:
+    name: nix flake check
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout 🛎️
+        uses: actions/checkout@v3
+
+      - name: Install Nix ❄
+        uses: DeterminateSystems/nix-installer-action@v9
+
+      - name: Run the Magic Nix Cache 🔌
+        uses: DeterminateSystems/magic-nix-cache-action@v3
+
+      - name: Check the flake for errors
+        run: nix flake check
+
+  nix-fmt:
+    name: nix fmt
+    runs-on: ubuntu-latest
+    steps:
+      - name: Checkout 🛎️
+        uses: actions/checkout@v3
+
+      - name: Install Nix ❄
+        uses: DeterminateSystems/nix-installer-action@v9
+
+      - name: Run the Magic Nix Cache 🔌
+        uses: DeterminateSystems/magic-nix-cache-action@v3
+
+      - name: Check the formatting
+        run: nix fmt -- --check .
+
   evaluate-nix-shell:
     name: Evaluate the Nix shell
     runs-on: ubuntu-latest
@@ -11,10 +59,10 @@ jobs:
         uses: actions/checkout@v3
 
       - name: Install Nix ❄
-        uses: DeterminateSystems/nix-installer-action@v4
+        uses: DeterminateSystems/nix-installer-action@v9
 
       - name: Run the Magic Nix Cache 🔌
-        uses: DeterminateSystems/magic-nix-cache-action@v2
+        uses: DeterminateSystems/magic-nix-cache-action@v3
 
       - name: Evaluate the Nix shell
         run: nix develop -c "true"

.gitignore

@@ -1,6 +1,10 @@
 # Rust
 /target
 
+# Nix
+/result
+/result-*
+
 # direnv
 /.direnv
 

Cargo.toml

@@ -1,5 +1,10 @@
 [workspace]
 resolver = "2"
+
+package.version = "0.1.0"
+package.edition = "2021"
+package.license = "Apache-2.0"
+
 members = [
   "rust-connector-sdk",
 ]

flake.nix

@@ -7,48 +7,96 @@
 # the line, `use flake`.
 
 {
-  description = "ndc-sdk";
+  description = "ndc-hub";
 
   inputs = {
-    flake-utils.url = github:numtide/flake-utils;
-    nixpkgs.url = github:NixOS/nixpkgs/master;
+    flake-utils.url = "github:numtide/flake-utils";
+    nixpkgs.url = "github:NixOS/nixpkgs/master";
+
+    crane = {
+      url = "github:ipetkov/crane";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+
+    rust-overlay = {
+      url = "github:oxalica/rust-overlay";
+      inputs = {
+        nixpkgs.follows = "nixpkgs";
+        flake-utils.follows = "flake-utils";
+      };
+    };
   };
 
   outputs =
     { self
     , flake-utils
     , nixpkgs
+    , crane
+    , rust-overlay
     }:
     flake-utils.lib.eachDefaultSystem (system:
     let
-      pkgs = import nixpkgs { inherit system; };
-    in
-    {
-      devShells.default = pkgs.mkShell {
+      pkgs = import nixpkgs {
+        inherit system;
+        overlays = [ rust-overlay.overlays.default ];
+      };
+      rustToolchain = pkgs.rust-bin.fromRustupToolchainFile ./rust-toolchain.toml;
+      craneLib = (crane.mkLib pkgs).overrideToolchain rustToolchain;
+
+      buildArgs = with pkgs; {
+        pname = "ndc-sdk";
+
+        src = craneLib.cleanCargoSource (craneLib.path ./.);
+
+        strictDeps = true;
+
+        # build-time inputs
         nativeBuildInputs = [
-          pkgs.cargo
-          pkgs.cargo-edit
-          pkgs.cargo-machete
-          pkgs.cargo-nextest
-          pkgs.cargo-watch
-          pkgs.clippy
-          pkgs.rust-analyzer
-          pkgs.rustPlatform.rustcSrc
-          pkgs.rustc
-          pkgs.rustfmt
-
-          pkgs.just
+          openssl.dev # required to build Rust crates that can conduct TLS connections
+          pkg-config # required to find OpenSSL
         ];
 
-        buildInputs = pkgs.lib.optionals pkgs.stdenv.isDarwin [
-          pkgs.darwin.apple_sdk.frameworks.Security
-          pkgs.darwin.apple_sdk.frameworks.SystemConfiguration
-          pkgs.libiconv
-        ]
+        # runtime inputs
+        buildInputs = [
+          openssl # required for TLS connections
+          protobuf # required by opentelemetry-proto, a dependency of axum-tracing-opentelemetry
+        ] ++ lib.optionals hostPlatform.isDarwin [
+          # macOS-specific dependencies
+          libiconv
+          darwin.apple_sdk.frameworks.CoreFoundation
+          darwin.apple_sdk.frameworks.Security
+          darwin.apple_sdk.frameworks.SystemConfiguration
+        ];
+      };
+    in
+    {
+      packages = {
+        deps = craneLib.buildDepsOnly buildArgs;
+        default = craneLib.buildPackage
+          (buildArgs // {
+            cargoArtifacts = self.packages.${system}.deps;
+            doCheck = false;
+          });
+      };
+
+      apps = {
+        example = flake-utils.lib.mkApp {
+          drv = self.packages.${system}.default;
+          exePath = "/bin/ndc_hub_example";
+        };
+      };
+
+      devShells.default = with pkgs; mkShell {
+        inputsFrom = [ self.packages.${system}.default ];
+
+        nativeBuildInputs = [
+          rustToolchain
+          cargo-edit
+          cargo-machete
+          cargo-nextest
+          cargo-watch
 
-        ++ pkgs.lib.optionals pkgs.stdenv.isLinux [
-          pkgs.pkg-config
-          pkgs.openssl
+          just
         ];
       };
 

justfile

@@ -15,9 +15,11 @@ dev:
 
 format:
   cargo fmt --all
+  ! command -v nix > /dev/null || nix fmt
 
 format-check:
   cargo fmt --all --check
+  ! command -v nix > /dev/null || nix fmt -- --check .
 
 lint:
   cargo clippy --all-targets --all-features

rust-connector-sdk/Cargo.toml

@@ -1,7 +1,8 @@
 [package]
 name = "ndc-sdk"
-version = "0.1.0"
-edition = "2021"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
 
 [lib]
 name = "ndc_sdk"