Add cargo-watch, demonstrating addition of build tools

README.md

@@ -5,13 +5,13 @@ See [Nix-ifying Rust projects](https://notes.srid.ca/rust-nix) for details.
 ## Adapting this template
 
 - Change `name` in Cargo.toml and flake.nix. Also change `description` in flake.nix.
-- There are two CI workflows, and one of them uses Nix which is slower than the other based on rustup. Pick one or the other depending on your trade-offs.
+- There are two CI workflows, and one of them uses Nix which is slower (unless you configure a cache) than the other that is based on rustup. Pick one or the other depending on your trade-offs.
 
 ## Development (Flakes)
 
 This repo uses [Flakes](https://nixos.wiki/wiki/Flakes) from the get-go, but compat is provided for traditional nix-shell/nix-build as well (see the section below).
 
-```
+```bash
 # Dev shell
 nix develop
 
@@ -27,7 +27,7 @@ nix build
 
 ## Development (Legacy Nix)
 
-```
+```bash
 # Dev shell
 nix-shell
 

flake.nix

@@ -63,7 +63,7 @@
 
           # Configuration for the non-Rust dependencies
           buildInputs = with pkgs; [ openssl.dev ];
-          nativeBuildInputs = with pkgs; [ rustc cargo pkgconfig nixpkgs-fmt ];
+          nativeBuildInputs = with pkgs; [ rustc cargo pkgconfig ];
         in
         rec {
           packages.${name} = project.rootCrate.build;
@@ -81,7 +81,14 @@
           # `nix develop`
           devShell = pkgs.mkShell
             {
-              inherit buildInputs nativeBuildInputs;
+              inputsFrom = builtins.attrValues self.packages.${system};
+              buildInputs = buildInputs ++ (with pkgs;
+                # Tools you need for development go here.
+                [
+                  nixpkgs-fmt
+                  cargo-watch
+                ]);
+              # FIXME: Is this correct? Should it use rust-overlay instead?
               RUST_SRC_PATH = "${pkgs.rust.packages.stable.rustPlatform.rustLibSrc}";
             };
         }