Merge pull request #717 from hercules-ci/fix-doc-revision

Fix doc revision eval error

default.nix

@@ -10,10 +10,15 @@ let
 
   eval = evalConfig {
     inherit system;
-    modules = [ configuration ];
+    modules = [ configuration nixpkgsRevisionModule ];
     inputs = { inherit nixpkgs; };
   };
 
+  nixpkgsRevisionModule =
+    if nixpkgs?rev && lib.isString nixpkgs.rev
+    then { system.nixpkgsRevision = nixpkgs.rev; }
+    else { };
+
   # The source code of this repo needed by the [un]installers.
   nix-darwin = lib.cleanSource (
     lib.cleanSourceWith {

modules/documentation/default.nix

@@ -1,4 +1,4 @@
-{ config, lib, pkgs, baseModules, modules, ... }:
+toplevel@{ config, lib, pkgs, baseModules, modules, ... }:
 
 with lib;
 
@@ -25,7 +25,15 @@ let
     inherit pkgs config;
     version = config.system.darwinVersion;
     revision = config.system.darwinRevision;
-    nixpkgsRevision = config.system.nixpkgsRevision;
+    nixpkgsRevision =
+      if toplevel.options.system.nixpkgsRevision.isDefined
+        then config.system.nixpkgsRevision
+
+        # If user does not use flakes and does not add rev to nixpkgs, we don't
+        # know which revision or even branch they're on. In this case we still want
+        # to link somewhere, so we hope that master hasn't changed too much.
+        else "master";
+
     options =
       let
         scrubbedEval = evalModules {