nixos/kismet: fix module typechecking

70ab11c2f2 added the new v2 merge, which
performs typechecking at the same time as merging. We need to opt out of
this optimization, as it changes the behavior of the module and results
in eval errors.

nixos/modules/services/networking/kismet.nix

@@ -28,7 +28,14 @@ let
     typeOf
     match
     ;
-  inherit (lib.lists) all isList flatten;
+  inherit (lib.lists)
+    all
+    isList
+    head
+    tail
+    flatten
+    foldl'
+    ;
   inherit (lib.attrsets)
     attrsToList
     filterAttrs
@@ -48,19 +55,60 @@ let
     in
     prev
     // {
-      check = value: prev.check value && (override type value);
+      check =
+        value:
+        let
+          prevResult = builtins.tryEval (prev.check value);
+          nextResult = builtins.tryEval (override type value);
+        in
+        prevResult.success && prevResult.value && nextResult.success && nextResult.value;
+
+      # We need to typecheck prior to merging, so deoptimize in case prev.merge is a functor.
+      merge = opts: prev.merge opts;
     };
 
   # Deep listOf.
-  listOf' = deep types.listOf (type: value: all type.check value);
+  inherit (types) listOf;
+  listOf' = deep listOf (type: value: all type.check value);
 
   # Deep attrsOf.
-  attrsOf' = deep types.attrsOf (type: value: all (item: type.check item.value) (attrsToList value));
+  inherit (types) attrsOf;
+  attrsOf' = deep attrsOf (type: value: all (item: type.check item.value) (attrsToList value));
+
+  # Deep either and oneOf that performs typecheck prior to merging.
+  inherit (types) either;
+  either' =
+    first: second:
+    let
+      prev = either first second;
+    in
+    prev
+    // {
+      check =
+        value:
+        let
+          firstResult = builtins.tryEval (first.check value);
+          secondResult = builtins.tryEval (second.check value);
+        in
+        firstResult.success && firstResult.value || secondResult.success && secondResult.value;
+
+      # We need to typecheck prior to merging, so deoptimize in case prev.merge is a functor.
+      merge = opts: prev.merge opts;
+    };
+
+  oneOf' =
+    ts:
+    let
+      head' =
+        if ts == [ ] then throw "types.oneOf needs to get at least one type in its argument" else head ts;
+      tail' = tail ts;
+    in
+    foldl' either' head' tail';
 
   # Kismet config atoms.
   atom =
     with types;
-    oneOf [
+    oneOf' [
       number
       bool
       str
@@ -68,7 +116,10 @@ let
 
   # Composite types.
   listOfAtom = listOf' atom;
-  atomOrList = with types; either atom listOfAtom;
+  atomOrList = oneOf' [
+    atom
+    listOfAtom
+  ];
   lists = listOf' atomOrList;
   kvPair = attrsOf' atomOrList;
   kvPairs = listOf' kvPair;
@@ -80,19 +131,17 @@ let
   # Toplevel config type.
   topLevel =
     let
-      topLevel' =
+      topLevel' = oneOf' [
-        with types;
+        headerKvPairs
-        oneOf [
+        headerKvPair
-          headerKvPairs
+        kvPairs
-          headerKvPair
+        kvPair
-          kvPairs
+        listOfAtom
-          kvPair
+        lists
-          listOfAtom
+        atom
-          lists
+      ];
-          atom
-        ];
     in
-    topLevel'
+    attrsOf' topLevel'
     // {
       description = "Kismet config stanza";
     };
@@ -239,7 +288,7 @@ in
         https://www.kismetwireless.net/docs/readme/configuring/configfiles/
       '';
       default = { };
-      type = with types; attrsOf topLevel;
+      type = topLevel;
       example = literalExpression ''
         {
           /* Examples for atoms */