add(ci): check for msrv (#1522)

.github/workflows/nix.yml

@@ -13,7 +13,7 @@ jobs:
     runs-on: ubuntu-latest
     name: "nix build"
     environment: cachix
-    timeout-minutes: 25
+    timeout-minutes: 35
     steps:
       - uses: actions/checkout@v3
         with:
@@ -27,3 +27,24 @@ jobs:
           authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
       - run: |
           nix build || nix build --substituters 'https://cache.nixos.org' --extra-substituters ''
+  build-msrv:
+    runs-on: ubuntu-latest
+    name: "build msrv"
+    environment: cachix
+    timeout-minutes: 35
+    steps:
+      - uses: actions/checkout@v3
+        with:
+          # Nix Flakes doesn't work on shallow clones
+          fetch-depth: 0
+      - uses: cachix/install-nix-action@v17
+      - uses: cachix/cachix-action@v10
+        with:
+          name: zellij
+          # If you chose API tokens for write access OR if you have a private cache
+          authToken: '${{ secrets.CACHIX_AUTH_TOKEN }}'
+      - run: |
+          nix build .#zellij-msrv || nix build .#zellij-msrv --substituters 'https://cache.nixos.org' --extra-substituters ''
+      - if: ${{ failure() }}
+        run: |
+          echo "::error :: If this is the only ci step failing, it is likely that the MSRV needs to be bumped.

nix/default.nix

@@ -32,6 +32,16 @@ flake-utils.lib.eachSystem [
     ];
   };
 
+  crate2nixMsrvPkgs = import nixpkgs {
+    inherit system;
+    overlays = [
+      (self: _: {
+        rustc = msrvToolchain;
+        cargo = msrvToolchain;
+      })
+    ];
+  };
+
   name = "zellij";
   pname = name;
   root = self;
@@ -40,9 +50,16 @@ flake-utils.lib.eachSystem [
 
   src = pkgs.nix-gitignore.gitignoreSource ignoreSource root;
 
-  cargoToml = builtins.fromTOML (builtins.readFile (src + ./Cargo.toml));
+  cargoToml = builtins.fromTOML (builtins.readFile (src + "/Cargo.toml"));
+  toolchainToml = builtins.fromTOML (builtins.readFile (src + "/rust-toolchain.toml"));
   rustToolchainToml = pkgs.rust-bin.fromRustupToolchainFile (src + "/rust-toolchain.toml");
 
+  msrvToolchain = pkgs.rust-bin.fromRustupToolchain {
+    channel = cargoToml.package.rust-version;
+    components = toolchainToml.toolchain.components;
+    targets = toolchainToml.toolchain.targets;
+  };
+
   cargoLock = {
     lockFile = builtins.path {
       path = src + "/Cargo.lock";
@@ -160,6 +177,19 @@ in rec {
     nativeBuildInputs = nativeBuildInputs ++ defaultPlugins;
   };
 
+  packages.zellij-msrv = crate2nixMsrvPkgs.callPackage ./crate2nix.nix {
+    inherit
+      name
+      src
+      crate2nix
+      desktopItems
+      postInstall
+      patchPhase
+      meta
+      ;
+    nativeBuildInputs = nativeBuildInputs ++ defaultPlugins;
+  };
+
   # native nixpkgs support - keep supported
   packages.zellij-native = (pkgs.makeRustPlatform {inherit cargo rustc;}).buildRustPackage {
     inherit