Merge pull request #215 from mdboom/fix-hiwire-iterator

Fix iterators passed from Javascript to Python

src/hiwire.c

@@ -249,16 +249,32 @@ MAKE_OPERATOR(greater_than, >);
 MAKE_OPERATOR(greater_than_equal, >=);
 
 EM_JS(int, hiwire_next, (int idobj), {
-  var jsobj = Module.hiwire_get_value(idobj);
   // clang-format off
-  if (jsobj.next === undefined) {
+  if (idobj === -2) {
     // clang-format on
-    return HW_ERROR;
+    return -1;
   }
 
+  var jsobj = Module.hiwire_get_value(idobj);
   return Module.hiwire_new_value(jsobj.next());
 });
 
+EM_JS(int, hiwire_get_iterator, (int idobj), {
+  // clang-format off
+  if (idobj === -2) {
+    return -1;
+  }
+
+  var jsobj = Module.hiwire_get_value(idobj);
+  if (typeof jsobj.next ===  'function') {
+    return Module.hiwire_new_value(jsobj);
+  } else if (typeof jsobj[Symbol.iterator] === 'function') {
+    return Module.hiwire_new_value(jsobj[Symbol.iterator]())
+  }
+  return -1;
+  // clang-format on
+})
+
 EM_JS(int, hiwire_nonzero, (int idobj), {
   var jsobj = Module.hiwire_get_value(idobj);
   return (jsobj != 0) ? 1 : 0;

src/hiwire.h

@@ -366,6 +366,12 @@ hiwire_greater_than_equal(int ida, int idb);
 int
 hiwire_next(int idobj);
 
+/**
+ * Returns the iterator associated with the given object, if any.
+ */
+int
+hiwire_get_iterator(int idobj);
+
 /**
  * Returns 1 if the value is non-zero.
  *

src/jsproxy.c

@@ -169,8 +169,16 @@ JsProxy_RichCompare(PyObject* a, PyObject* b, int op)
 static PyObject*
 JsProxy_GetIter(PyObject* o)
 {
-  Py_INCREF(o);
-  return o;
+  JsProxy* self = (JsProxy*)o;
+
+  int iditer = hiwire_get_iterator(self->js);
+
+  if (iditer == HW_ERROR) {
+    PyErr_SetString(PyExc_TypeError, "Object is not iterable");
+    return NULL;
+  }
+
+  return js2python(iditer);
 }
 
 static PyObject*
@@ -375,6 +383,10 @@ static PyMethodDef JsProxy_Methods[] = {
     (PyCFunction)JsProxy_New,
     METH_VARARGS | METH_KEYWORDS,
     "Construct a new instance" },
+  { "__iter__",
+    (PyCFunction)JsProxy_GetIter,
+    METH_NOARGS,
+    "Get an iterator over the object" },
   { "_has_bytes",
     (PyCFunction)JsProxy_HasBytes,
     METH_NOARGS,

test/test_python.py

@@ -325,8 +325,14 @@ def test_jsproxy_implicit_iter(selenium):
         """
         window.ITER = [1, 2, 3];""")
     assert selenium.run(
-        "from js import ITER\n"
+        "from js import ITER, Object\n"
+        "list(ITER)") == [1, 2, 3]
+    assert selenium.run(
+        "from js import ITER, Object\n"
         "list(ITER.values())") == [1, 2, 3]
+    assert selenium.run(
+        "from js import ITER, Object\n"
+        "list(Object.values(ITER))") == [1, 2, 3]
 
 
 def test_open_url(selenium):