Stop responding to methods not defined in JS object

When passing JS::Object to `Kernel.puts`, it tries to convert the object
to `Array` by `to_ary`. `JS::Object` pretended to be able to respond to
`to_ary` without any check, but the inner JS Object doesn't have such
method, so it caused mysterious error.

This patch adds `JS::Object#respond_to_missing?` definition to avoid
calling undefined method through `#method_missing`.

Author: kateinoigakukun

ext/js/lib/js.rb

@@ -1,7 +1,16 @@
 require "js.so"
 
 class JS::Object
-    def method_missing(name, *args, &block)
-        self.call(name, *args, &block)
+    def method_missing(sym, *args, &block)
+        if self[sym].typeof == "function"
+            self.call(sym, *args, &block)
+        else
+            super
+        end
+    end
+
+    def respond_to_missing?(sym, include_private)
+        return true if super
+        self[sym].typeof == "function"
     end
 end

packages/npm-packages/ruby-wasm-wasi/test/package.test.ts

@@ -51,5 +51,5 @@ describe("Packaging validation", () => {
     const mod = await WebAssembly.compile(binary.buffer);
     const nameSections = WebAssembly.Module.customSections(mod, "name");
     expect(nameSections.length).toBe(1);
-  })
+  });
 });

packages/npm-packages/ruby-wasm-wasi/test/unit/object.test.ts

@@ -0,0 +1,17 @@
+import { initRubyVM } from "./../init";
+
+describe("JS::Object", () => {
+  jest.setTimeout(10 /*sec*/ * 1000);
+  describe("#method_missing", () => {
+    test("raise NoMethodError if method is not defined in JS", async () => {
+      const vm = await initRubyVM();
+      const obj = vm.eval(`
+                require 'js'
+                obj = JS.eval(<<~JS)
+                    return { foo() { return true; } };
+                JS
+            `);
+      expect(() => obj.call("bar")).toThrowError();
+    });
+  });
+});