Fix #388: Support dir(x) on JsProxies (#393)

src/hiwire.c

@@ -241,6 +241,15 @@ EM_JS(void, hiwire_delete_member_obj, (int idobj, int ididx), {
   delete jsobj[jsidx];
 });
 
+EM_JS(int, hiwire_dir, (int idobj), {
+  var jsobj = Module.hiwire_get_value(idobj);
+  var result = [];
+  do {
+    result.push.apply(result, Object.getOwnPropertyNames(jsobj));
+  } while ((jsobj = Object.getPrototypeOf(jsobj)));
+  return Module.hiwire_new_value(result);
+});
+
 EM_JS(int, hiwire_call, (int idfunc, int idargs), {
   var jsfunc = Module.hiwire_get_value(idfunc);
   var jsargs = Module.hiwire_get_value(idargs);

src/hiwire.h

@@ -346,6 +346,13 @@ hiwire_set_member_obj(int idobj, int ididx, int idval);
 void
 hiwire_delete_member_obj(int idobj, int ididx);
 
+/**
+ * Get the methods on an object, both on itself and what it inherits.
+ *
+ */
+int
+hiwire_dir(int idobj);
+
 /**
  * Call a function
  *

src/jsproxy.c

@@ -383,6 +383,17 @@ JsProxy_HasBytes(PyObject* o)
   }
 }
 
+static PyObject*
+JsProxy_Dir(PyObject* o)
+{
+  JsProxy* self = (JsProxy*)o;
+
+  int iddir = hiwire_dir(self->js);
+  PyObject* pydir = js2python(iddir);
+  hiwire_decref(iddir);
+  return pydir;
+}
+
 // clang-format off
 static PyMappingMethods JsProxy_MappingMethods = {
   JsProxy_length,
@@ -408,6 +419,10 @@ static PyMethodDef JsProxy_Methods[] = {
     (PyCFunction)JsProxy_HasBytes,
     METH_NOARGS,
     "Returns true if instance has buffer memory. For testing only." },
+  { "__dir__",
+    (PyCFunction)JsProxy_Dir,
+    METH_NOARGS,
+    "Returns a list of the members and methods on the object." },
   { NULL }
 };
 // clang-format on

test/test_python.py

@@ -443,6 +443,13 @@ def test_jsproxy(selenium):
         dict(TEST) == {'foo': 'bar', 'baz': 'bap'}
         """
     ) is True
+    assert selenium.run(
+        """
+        from js import document
+        el = document.createElement('div')
+        len(dir(el)) >= 200 and 'appendChild' in dir(el)
+        """
+    ) is True
 
 
 def test_jsproxy_iter(selenium):