feat: reify requests (#42)

lib/make.nix

@@ -25,18 +25,29 @@ let
     in
     lib.mkRequest [ maybeLocatedRequest ];
 
+  # Apply specific transformations to the request's configData & extra
+  reifiedRequest = userRequest // {
+    configData = userRequest.apply userRequest.configData;
+    hook = userRequest.hook // {
+      extra =
+        if builtins.isFunction userRequest.hook.extra
+        then userRequest.hook.extra userRequest.configData
+        else userRequest.hook.extra;
+    };
+  };
+
   # The defined interface between Nixago and an engine is that it takes exactly
   # one parameter: an instance of the request module. The result should be a
   # derivation which builds the desired configuration file.
-  configFile = userRequest.engine userRequest;
+  configFile = userRequest.engine reifiedRequest;
 
   # TODO: Remove this once we convert everything over to the new framework
   name = "temp";
 
   # TODO: Simplify this once we convert everything over to the new framework
   hookConfig = {
-    inherit (userRequest) output;
-    inherit (userRequest.hook) extra mode;
+    inherit (reifiedRequest) output;
+    inherit (reifiedRequest.hook) extra mode;
   };
 
   # Builds the shell hook for managing the generated file.

modules/request.nix

@@ -10,7 +10,7 @@ let
       options = {
         # TODO: Make this a list
         extra = mkOption {
-          type = types.str;
+          type = types.either types.str (types.functionTo types.str);
           description = "Shell code to run when the file is updated";
           default = "";
         };
@@ -50,6 +50,11 @@ in
       description = "Additional options for controlling hook generation";
       default = { };
     };
+    apply = mkOption {
+      type = types.functionTo types.anything;
+      description = "Apply this transformation to `configData`";
+      default = x: x;
+    };
     output = mkOption {
       type = types.str;
       description = "The relative path to link the generated file";