introduce dev flake

Keep the number of exposed inputs from the top-level flake small by
splitting the development environment into its own flake.

The .envrc uses `--override-input srvos path:$PATH` so that the srvos
path always get re-calculated on reload, but not recorded. Since the
hash of srvos is stored inside of srvos, it would infinitely update
otherwise.

.envrc

@@ -0,0 +1 @@
+use flake ./dev --override-input srvos "path:$PWD"

.github/workflows/gh-pages.yml

@@ -35,4 +35,4 @@ jobs:
         if: ${{ github.ref == 'refs/heads/main' }}
         with:
           github_token: ${{ secrets.GITHUB_TOKEN }}
-          publish_dir: "${{ steps.build.outputs.result }}/"
+          publish_dir: "${{ steps.build.outputs.result }}/"

default.nix

@@ -1,11 +1,14 @@
 # This file provides backward compatibility to nix < 2.4 clients
-{ system ? builtins.currentSystem }:
+{ system ? builtins.currentSystem, src ? ./. }:
 let
-  flake-compat = builtins.fetchTarball {
-    url = "https://github.com/edolstra/flake-compat/archive/35bb57c0c8d8b62bbfd284272c928ceb64ddbde9.tar.gz";
-    sha256 = "sha256-4gtG9iQuiKITOjNQQeQIpoIB6b16fm+504Ch3sNKLd8=";
+  lock = builtins.fromJSON (builtins.readFile ./dev/flake.lock);
+  inherit (lock.nodes.flake-compat.locked) owner repo rev narHash;
+
+  flake-compat = fetchTarball {
+    url = "https://github.com/${owner}/${repo}/archive/${rev}.tar.gz";
+    sha256 = narHash;
   };
 
-  flake = import flake-compat { src = ./.; inherit system; };
+  flake = import flake-compat { inherit src system; };
 in
 flake.defaultNix

dev/flake.lock

@@ -0,0 +1,83 @@
+{
+  "nodes": {
+    "flake-compat": {
+      "locked": {
+        "lastModified": 1680466377,
+        "narHash": "sha256-0mh4l/e5kLCf2SL6TFzi5hDZfXlwRmiMcHnczeZNu28=",
+        "owner": "nix-community",
+        "repo": "flake-compat",
+        "rev": "f5aab912cd8069e882de9a5847650be52a6c28df",
+        "type": "github"
+      },
+      "original": {
+        "owner": "nix-community",
+        "repo": "flake-compat",
+        "type": "github"
+      }
+    },
+    "nixpkgs": {
+      "locked": {
+        "lastModified": 1680024716,
+        "narHash": "sha256-f9824KWmxVBI4WLI7o6tDFfj+dW+qj6uQKo0ZRsbaZQ=",
+        "owner": "NixOS",
+        "repo": "nixpkgs",
+        "rev": "49079a134fd3d3ac25d5ae1f5516f37770f19138",
+        "type": "github"
+      },
+      "original": {
+        "owner": "NixOS",
+        "ref": "nixos-unstable-small",
+        "repo": "nixpkgs",
+        "type": "github"
+      }
+    },
+    "root": {
+      "inputs": {
+        "flake-compat": "flake-compat",
+        "nixpkgs": [
+          "srvos",
+          "nixpkgs"
+        ],
+        "srvos": "srvos",
+        "treefmt-nix": "treefmt-nix"
+      }
+    },
+    "srvos": {
+      "inputs": {
+        "nixpkgs": "nixpkgs"
+      },
+      "locked": {
+        "lastModified": 0,
+        "narHash": "sha256-GysuOf3OrDRY5Sg2Y1KoRlTtWovFQkz8DNe1kcDDZ0E=",
+        "path": "../",
+        "type": "path"
+      },
+      "original": {
+        "path": "../",
+        "type": "path"
+      }
+    },
+    "treefmt-nix": {
+      "inputs": {
+        "nixpkgs": [
+          "nixpkgs"
+        ]
+      },
+      "locked": {
+        "lastModified": 1680218481,
+        "narHash": "sha256-VhkSVeKXbZtdaT41Kn3QuFE7OnXHM4UbMlqBez+tRL0=",
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "rev": "a082287718105c284475df18b882a76312dea0d0",
+        "type": "github"
+      },
+      "original": {
+        "owner": "numtide",
+        "repo": "treefmt-nix",
+        "type": "github"
+      }
+    }
+  },
+  "root": "root",
+  "version": 7
+}

dev/flake.nix

@@ -0,0 +1,34 @@
+{
+  description = "srvos dev flake";
+
+  inputs.srvos.url = "path:../";
+
+  inputs.nixpkgs.follows = "srvos/nixpkgs";
+
+  inputs.treefmt-nix.url = "github:numtide/treefmt-nix";
+  inputs.treefmt-nix.inputs.nixpkgs.follows = "nixpkgs";
+
+  inputs.flake-compat.url = "github:nix-community/flake-compat";
+
+  outputs = { self, nixpkgs, treefmt-nix, srvos, ... }:
+    let
+      eachSystem = f:
+        nixpkgs.lib.genAttrs
+          srvos.lib.supportedSystems
+          (system: f nixpkgs.legacyPackages.${system});
+
+      treefmt = eachSystem (pkgs: treefmt-nix.lib.mkWrapper pkgs ./treefmt.nix);
+    in
+    {
+      formatter = eachSystem (pkgs: treefmt.${pkgs.system});
+
+      devShells = eachSystem (pkgs: {
+        default = pkgs.mkShellNoCC {
+          packages = [
+            pkgs.nixpkgs-fmt
+            treefmt.${pkgs.system}
+          ];
+        };
+      });
+    };
+}

dev/treefmt.nix

@@ -0,0 +1,4 @@
+{
+  projectRootFile = ".git/config";
+  programs.nixpkgs-fmt.enable = true;
+}

flake.nix

@@ -7,15 +7,17 @@
     let
       eachSystem = f:
         nixpkgs.lib.genAttrs
-          [
-            "aarch64-darwin"
-            "aarch64-linux"
-            "x86_64-darwin"
-            "x86_64-linux"
-          ]
+          self.lib.supportedSystems
           (system: f { inherit self system; pkgs = nixpkgs.legacyPackages.${system}; });
     in
     {
+      lib.supportedSystems = [
+        "aarch64-darwin"
+        "aarch64-linux"
+        "x86_64-darwin"
+        "x86_64-linux"
+      ];
+
       packages = eachSystem ({ pkgs, ... }: {
         docs = pkgs.callPackage ./docs { };
       });

shell.nix

@@ -1,3 +1,5 @@
 { system ? builtins.currentSystem }:
-(import ./default.nix { inherit system; }).devShells.${system}.default
-  or throw "dev-shell not defined. Cannot find flake attribute devShells.${system}.default"
+let
+  d = import ./. { inherit system; src = ./dev; };
+in
+d.devShells.${system}.default