Add example for using an alternative cargo registry

.gitignore

@@ -1,2 +1,3 @@
+/examples/*/flake.lock
 /result*
 target/

README.md

@@ -13,7 +13,9 @@ A [Nix](https://nixos.org/) library for building [cargo](https://doc.rust-lang.o
 Examples can be found [here](./examples). Detailed [API docs] are available, but
 at a glance, the following are supported:
 * Automatic vendoring of dependencies in a way that works with Nix
-  - Private registry and git dependency support coming soon!
+  - Alternative cargo registries are supported (with a minor configuration
+    change)
+  - Git dependency support coming soon!
 * Reusing dependency artifacts after only building them once
 * [clippy](https://github.com/rust-lang/rust-clippy) checks
 * [rustfmt](https://github.com/rust-lang/rustfmt) checks
@@ -32,6 +34,9 @@ nix flake init -t github:ipetkov/crane#quick-start-simple
 
 # If you need a custom rust toolchain (e.g. to build WASM targets):
 nix flake init -t github:ipetkov/crane#custom-toolchain
+
+# If you need to use another crate registry besides crates.io
+nix flake init -t github:ipetkov/crane#alt-registry
 ```
 
 For an even more lean, no frills set up, create a `flake.nix` file with the

checks/alt-registry/src/main.rs

@@ -1,6 +0,0 @@
-use std::any::TypeId;
-
-fn main() {
-    println!("byteorder::LittleEndian: {:?}", TypeId::of::<byteorder::LittleEndian>());
-    println!("epitech_api::Client: {:?}", TypeId::of::<epitech_api::Client>());
-}

checks/default.nix

@@ -103,7 +103,7 @@ onlyDrvs (lib.makeScope myLib.newScope (self:
         ];
       in
       myLibWithRegistry.buildPackage {
-        src = ./alt-registry;
+        src = ../examples/alt-registry;
         nativeBuildInputs = with pkgs; [
           pkgconfig
           openssl

examples/README.md

@@ -2,6 +2,8 @@
 
 This directory contains several different ways of configuring a project:
 
+* **alt-registry**: build a cargo project which uses another crate registry
+  besides crates.io
 * **custom-toolchain**: build a cargo project with a custom toolchain (e.g. WASM
   builds)
 * **quick-start**: build a cargo project with a comprehensive test suite

examples/alt-registry/flake.nix

@@ -0,0 +1,83 @@
+{
+  description = "Build a cargo project with alternative crate registries";
+
+  inputs = {
+    nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
+
+    crane = {
+      url = "github:ipetkov/crane";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+
+    flake-utils = {
+      url = "github:numtide/flake-utils";
+      inputs.nixpkgs.follows = "nixpkgs";
+    };
+  };
+
+  outputs = { self, nixpkgs, crane, flake-utils, ... }:
+    flake-utils.lib.eachDefaultSystem (system:
+      let
+        pkgs = import nixpkgs {
+          inherit system;
+        };
+
+        craneLibOrig = crane.lib.${system};
+        craneLib = craneLibOrig.appendCrateRegistries [
+          # Automatically infer the download URL from the registry's index
+          #
+          # Note that this approach requires checking out the full index at the specified revision
+          # and adding a copy to the Nix store.
+          #
+          # Also note that the specified git revision _does not need to track updates to the index
+          # itself_ as long as the pinned revision contains the most recent version of the
+          # registry's `config.json` file. In other words, this commit revision only needs to be
+          # updated if the `config.json` file changes the download endpoint for this registry.
+          (craneLibOrig.registryFromGitIndex {
+            url = "https://github.com/Hirevo/alexandrie-index";
+            rev = "90df25daf291d402d1ded8c32c23d5e1498c6725";
+          })
+
+          # As a more lightweight alternative, the `dl` endpoint of the registry's `config.json`
+          # file can be copied here to avoid needing to copy the index to the Nix store.
+          # (craneLibOrig.registryFromDownloadUrl {
+          #   url = "https://github.com/Hirevo/alexandrie-index";
+          #   dl = "https://crates.polomack.eu/api/v1/crates/{crate}/{version}/download";
+          # })
+        ];
+
+        my-crate = craneLib.buildPackage {
+          src = ./.;
+
+          # Specific to our example, but not always necessary in the general case.
+          nativeBuildInputs = with pkgs; [
+            pkgconfig
+            openssl
+          ];
+        };
+      in
+      {
+        checks = {
+          # Build the crate as part of `nix flake check` for convenience
+          inherit my-crate;
+        };
+
+        defaultPackage = my-crate;
+        packages.my-crate = my-crate;
+
+        apps.my-app = flake-utils.lib.mkApp {
+          drv = my-crate;
+        };
+        defaultApp = self.apps.${system}.my-app;
+
+        devShell = pkgs.mkShell {
+          inputsFrom = builtins.attrValues self.checks;
+
+          # Extra inputs can be added here
+          nativeBuildInputs = with pkgs; [
+            cargo
+            rustc
+          ];
+        };
+      });
+}

examples/alt-registry/src/main.rs

@@ -0,0 +1,9 @@
+use std::any::TypeId;
+
+fn main() {
+    let le = TypeId::of::<byteorder::LittleEndian>();
+    let client = TypeId::of::<epitech_api::Client>();
+
+    println!("TypeId of byteorder::LittleEndian (from crates.io): {:?}", le);
+    println!("TypeId of epitech_api::Client (from alexandrie): {:?}", client);
+}