1 files changed, 47 insertions, 21 deletions

diff --git a/modules/system/version.nix b/modules/system/version.nix
index 3effb50..54829d1 100644
--- a/modules/system/version.nix
+++ b/modules/system/version.nix
@@ -5,8 +5,6 @@ with lib;
 let
   cfg = config.system;
 
-  defaultStateVersion = options.system.stateVersion.default;
-
   # Based on `lib.trivial.revisionWithDefault` from nixpkgs.
   gitRevision = path:
     if pathIsGitRepo "${path}/.git"
@@ -34,9 +32,10 @@ in
 {
   options = {
     system.stateVersion = mkOption {
-      type = types.int;
-      default = 4;
-      description = lib.mdDoc ''
+      type = types.ints.between 1 config.system.maxStateVersion;
+      # TODO: Remove this default and the assertion below.
+      default = config.system.maxStateVersion;
+      description = ''
         Every once in a while, a new NixOS release may change
         configuration defaults in a way incompatible with stateful
         data. For instance, if the default version of PostgreSQL
@@ -49,16 +48,29 @@ in
       '';
     };
 
+    system.maxStateVersion = mkOption {
+      internal = true;
+      type = types.int;
+      default = 5;
+    };
+
     system.darwinLabel = mkOption {
       type = types.str;
-      description = lib.mdDoc "Label to be used in the names of generated outputs.";
+      description = "Label to be used in the names of generated outputs.";
+    };
+
+    system.darwinRelease = mkOption {
+      readOnly = true;
+      type = types.str;
+      default = (lib.importJSON ../../version.json).release;
+      description = "The nix-darwin release (e.g. `24.11`).";
     };
 
     system.darwinVersion = mkOption {
       internal = true;
       type = types.str;
-      default = "darwin${toString cfg.stateVersion}${cfg.darwinVersionSuffix}";
-      description = lib.mdDoc "The full darwin version (e.g. `darwin4.2abdb5a`).";
+      default = cfg.darwinRelease + cfg.darwinVersionSuffix;
+      description = "The full nix-darwin version (e.g. `24.11.2abdb5a`).";
     };
 
     system.darwinVersionSuffix = mkOption {
@@ -67,28 +79,29 @@ in
       default = if cfg.darwinRevision != null
         then ".${substring 0 7 cfg.darwinRevision}"
         else "";
-      description = lib.mdDoc "The short darwin version suffix (e.g. `.2abdb5a`).";
+      description = "The short nix-darwin version suffix (e.g. `.2abdb5a`).";
     };
 
     system.darwinRevision = mkOption {
       internal = true;
       type = types.nullOr types.str;
       default = gitRevision (toString ../..);
-      description = lib.mdDoc "The darwin git revision from which this configuration was built.";
+      description = "The darwin git revision from which this configuration was built.";
     };
 
     system.nixpkgsRelease = mkOption {
       readOnly = true;
       type = types.str;
       default = lib.trivial.release;
-      description = lib.mdDoc "The nixpkgs release (e.g. `16.03`).";
+      description = "The nixpkgs release (e.g. `24.11`).";
     };
 
+    # TODO: Shouldn’t mismatch the Darwin release, rethink all this…
     system.nixpkgsVersion = mkOption {
       internal = true;
       type = types.str;
       default = cfg.nixpkgsRelease + cfg.nixpkgsVersionSuffix;
-      description = lib.mdDoc "The full nixpkgs version (e.g. `16.03.1160.f2d4ee1`).";
+      description = "The full nixpkgs version (e.g. `24.11.1160.f2d4ee1`).";
     };
 
     system.nixpkgsVersionSuffix = mkOption {
@@ -97,7 +110,7 @@ in
       default = if useSourceRevision
         then ".${lib.substring 0 8 (nixpkgsSrc.lastModifiedDate or nixpkgsSrc.lastModified or "19700101")}.${nixpkgsSrc.shortRev or "dirty"}"
         else lib.trivial.versionSuffix;
-      description = lib.mdDoc "The short nixpkgs version suffix (e.g. `.1160.f2d4ee1`).";
+      description = "The short nixpkgs version suffix (e.g. `.1160.f2d4ee1`).";
     };
 
     system.nixpkgsRevision = mkOption {
@@ -106,24 +119,37 @@ in
       default = if useSourceRevision && nixpkgsSrc ? rev
         then nixpkgsSrc.rev
         else lib.trivial.revisionWithDefault null;
-      description = lib.mdDoc "The nixpkgs git revision from which this configuration was built.";
+      description = "The nixpkgs git revision from which this configuration was built.";
     };
 
     system.configurationRevision = mkOption {
       type = types.nullOr types.str;
       default = null;
-      description = lib.mdDoc "The Git revision of the top-level flake from which this configuration was built.";
+      description = "The Git revision of the top-level flake from which this configuration was built.";
     };
   };
 
   config = {
     # This default is set here rather than up there so that the options
     # documentation is not reprocessed on every commit
-    system.darwinLabel = mkDefault "${cfg.nixpkgsVersion}+${cfg.darwinVersion}";
-
-    assertions = [ {
-      assertion = cfg.stateVersion <= defaultStateVersion;
-      message = "system.stateVersion = ${toString cfg.stateVersion}; is not a valid value";
-    } ];
+    system.darwinLabel = mkDefault cfg.darwinVersion;
+
+    assertions = [
+      {
+        assertion = options.system.stateVersion.highestPrio != (lib.mkOptionDefault { }).priority;
+        message = ''
+          The `system.stateVersion` option is not defined in your
+          nix-darwin configuration. The value is used to conditionalize
+          backwards‐incompatible changes in default settings. You should
+          usually set this once when installing nix-darwin on a new system
+          and then never change it (at least without reading all the relevant
+          entries in the changelog using `darwin-rebuild changelog`).
+
+          You can use the current value for new installations as follows:
+
+              system.stateVersion = ${toString config.system.maxStateVersion};
+        '';
+      }
+    ];
   };
 }