[#25] engine: fix serialization of helper options functions to ruby

lib/handlebars/engine.rb

@@ -84,9 +84,9 @@ def register_helper(name = nil, function = nil, **helpers, &block)
         case f
         when Proc
           attach(n, &f)
-          evaluate("registerHelper('#{n}', #{n})")
+          evaluate("registerRbHelper('#{n}', #{n})")
         when String, Symbol
-          evaluate("Handlebars.registerHelper('#{n}', #{f})")
+          evaluate("registerJsHelper('#{n}', #{f})")
         end
       end
     end

lib/handlebars/engine/init.js

@@ -16,14 +16,23 @@ var template = (spec) => {
 var registerPartial = Handlebars.registerPartial.bind(Handlebars);
 var unregisterPartial = Handlebars.unregisterPartial.bind(Handlebars);
 
-var registerHelper = (...args) => {
-  const fn = args[args.length - 1];
+var registerJsHelper = Handlebars.registerHelper.bind(Handlebars);
+
+var registerRbHelper = (name, fn) => {
   function wrapper(...args) {
+    // Ruby cannot access the `this` context, so pass it as the first argument.
     args.unshift(this);
+    const { ...options } = args[args.length-1];
+    Object.entries(options).forEach(([key, value]) => {
+      if (typeof value === "function") {
+        // functions are cannot be passed back to Ruby
+        options[key] = "function";
+      }
+    });
+    args[args.length-1] = options
     return fn(...args);
   }
-  args[args.length - 1] = wrapper;
-  return Handlebars.registerHelper(...args);
+  return registerJsHelper(name, wrapper);
 };
 
 var unregisterHelper = Handlebars.unregisterHelper.bind(Handlebars);

spec/handlebars/engine_spec.rb

@@ -255,7 +255,7 @@
         describe "the options" do
           it "includes the main block function" do
             opts = include(
-              "fn" => kind_of(MiniRacer::JavaScriptFunction),
+              "fn" => "function", # kind_of(MiniRacer::JavaScriptFunction),
             )
             args = [anything, any_args, opts]
             render
@@ -264,7 +264,7 @@
 
           it "includes the else block function" do
             opts = include(
-              "inverse" => kind_of(MiniRacer::JavaScriptFunction),
+              "inverse" => "function", # kind_of(MiniRacer::JavaScriptFunction),
             )
             args = [anything, any_args, opts]
             render
@@ -279,6 +279,14 @@
         <<~JS
           function (...args) {
             args.unshift(this);
+            const { ...options } = args[args.length-1];
+            Object.entries(options).forEach(([key, value]) => {
+              if (typeof value === "function") {
+                // functions are cannot be passed back to Ruby
+                options[key] = "function";
+              }
+            });
+            args[args.length-1] = options
             return tester(...args);
           }
         JS