feat(build): add flag to only generate .state's flake.(nix|lock)

build.sh

@@ -40,6 +40,10 @@ while [[ $# -gt 0 ]]; do
       export_full_config=1
       shift
       ;;
+    --genflake-only)
+      genflake_only=1
+      shift
+      ;;
     --update)
       update_all="1"
       update_core="1"
@@ -187,6 +191,13 @@ elif [ "$update_repos_inputs" == "1" ]; then
   )
 fi
 
+# Stop after the flake (and its lock) have been generated, without
+# building anything. Lets callers evaluate the generated flake (e.g. to
+# query per-package output paths) without realising the system closure.
+if [ "$genflake_only" == "1" ]; then
+  exit 0
+fi
+
 if [ "$export_full_config" == "1" ]; then
   (
     cd "$ICEDOS_STATE_DIR"

flake.nix

@@ -1,5 +1,10 @@
 {
   inputs = {
+    cache-server = {
+      flake = false;
+      url = "github:icedos/cache-server";
+    };
+
     nixpkgs.url = "github:NixOS/nixpkgs/nixpkgs-unstable";
   };
 

modules/cache.nix

@@ -0,0 +1,12 @@
+{ config, lib, ... }:
+
+let
+  inherit (lib) mkIf;
+  inherit (config.icedos.system.cache) enable key url;
+in
+{
+  nix.settings = mkIf enable {
+    substituters = [ url ];
+    trusted-public-keys = [ key ];
+  };
+}

modules/options.nix

@@ -6,7 +6,7 @@
 }:
 
 let
-  inherit (lib) types;
+  inherit (lib) readFile types;
 
   inherit (icedosLib)
     mkBoolOption
@@ -90,6 +90,12 @@ in
           resolution = mkStrOption { default = "1920x1080"; };
         };
 
+        cache = {
+          enable = mkBoolOption { default = true; };
+          key = mkStrOption { default = readFile "${inputs.icedos-core.inputs.cache-server}/nix-public.pem"; };
+          url = mkStrOption { default = "https://icedos.mirrors.knp.one"; };
+        };
+
         channels = mkSubmoduleListOption { default = [ ]; } {
           name = mkStrOption { };
           url = mkStrOption { };