Merge pull request #317 from Distributive-Network/philippe/for-of-iterable

Expand for-of loop support to iterable types

Author: philippedistributive

src/PyIterableProxyHandler.cc

@@ -21,6 +21,8 @@
 
 const char PyIterableProxyHandler::family = 0;
 
+// TODO merge shared _next code
+
 bool PyIterableProxyHandler::iterable_next(JSContext *cx, unsigned argc, JS::Value *vp) {
   JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
   JS::RootedObject thisObj(cx);
@@ -41,7 +43,7 @@ bool PyIterableProxyHandler::iterable_next(JSContext *cx, unsigned argc, JS::Val
         PyErr_Clear();
       }
       else {
-        return NULL;
+        return false;
       }
     }
 
@@ -66,10 +68,139 @@ JSMethodDef PyIterableProxyHandler::iterable_methods[] = {
   {NULL, NULL, 0}
 };
 
+
+// IterableIterator
+
+enum {
+  IterableIteratorSlotIterableObject,
+  IterableIteratorSlotCount
+};
+
+static JSClass iterableIteratorClass = {"IterableIterator", JSCLASS_HAS_RESERVED_SLOTS(IterableIteratorSlotCount)};
+
+static bool iterator_next(JSContext *cx, unsigned argc, JS::Value *vp) {
+  JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+  JS::RootedObject thisObj(cx);
+  if (!args.computeThis(cx, &thisObj)) return false;
+
+  PyObject *it = JS::GetMaybePtrFromReservedSlot<PyObject>(thisObj, IterableIteratorSlotIterableObject);
+
+  JS::RootedObject result(cx, JS_NewPlainObject(cx));
+
+  PyObject *(*iternext)(PyObject *) = *Py_TYPE(it)->tp_iternext;
+
+  PyObject *item = iternext(it);
+
+  if (item == NULL) {
+    if (PyErr_Occurred()) {
+      if (PyErr_ExceptionMatches(PyExc_StopIteration) ||
+          PyErr_ExceptionMatches(PyExc_SystemError)) {      // TODO this handles a result like   SystemError: Objects/dictobject.c:1778: bad argument to internal function. Why are we getting that?
+        PyErr_Clear();
+      }
+      else {
+        return false;
+      }
+    }
+
+    JS::RootedValue done(cx, JS::BooleanValue(true));
+    if (!JS_SetProperty(cx, result, "done", done)) return false;
+    args.rval().setObject(*result);
+    return result;
+  }
+
+  JS::RootedValue done(cx, JS::BooleanValue(false));
+  if (!JS_SetProperty(cx, result, "done", done)) return false;
+
+  JS::RootedValue value(cx, jsTypeFactory(cx, item));
+  if (!JS_SetProperty(cx, result, "value", value)) return false;
+
+  args.rval().setObject(*result);
+  return true;
+}
+
+static JSFunctionSpec iterable_iterator_methods[] = {
+  JS_FN("next", iterator_next, 0, JSPROP_ENUMERATE),
+  JS_FS_END
+};
+
+static bool IterableIteratorConstructor(JSContext *cx, unsigned argc, JS::Value *vp) {
+  JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+
+  if (!args.isConstructing()) {
+    JS_ReportErrorASCII(cx, "You must call this constructor with 'new'");
+    return false;
+  }
+
+  JS::RootedObject thisObj(cx, JS_NewObjectForConstructor(cx, &iterableIteratorClass, args));
+  if (!thisObj) {
+    return false;
+  }
+
+  args.rval().setObject(*thisObj);
+  return true;
+}
+
+static bool DefineIterableIterator(JSContext *cx, JS::HandleObject global) {
+  JS::RootedObject iteratorPrototype(cx);
+  if (!JS_GetClassPrototype(cx, JSProto_Iterator, &iteratorPrototype)) {
+    return false;
+  }
+
+  JS::RootedObject protoObj(cx,
+    JS_InitClass(cx, global,
+      nullptr, iteratorPrototype,
+      "IterableIterator",
+      IterableIteratorConstructor, 0,
+      nullptr, iterable_iterator_methods,
+      nullptr, nullptr)
+  );
+
+  return protoObj; // != nullptr
+}
+
+static bool iterable_values(JSContext *cx, unsigned argc, JS::Value *vp) {
+  JS::CallArgs args = JS::CallArgsFromVp(argc, vp);
+
+  JS::RootedObject proxy(cx, JS::ToObject(cx, args.thisv()));
+  if (!proxy) {
+    return false;
+  }
+
+  PyObject *self = JS::GetMaybePtrFromReservedSlot<PyObject>(proxy, PyObjectSlot);
+
+  JS::RootedObject global(cx, JS::GetNonCCWObjectGlobal(proxy));
+
+  JS::RootedValue constructor_val(cx);
+  if (!JS_GetProperty(cx, global, "IterableIterator", &constructor_val)) return false;
+  if (!constructor_val.isObject()) {
+    if (!DefineIterableIterator(cx, global)) {
+      return false;
+    }
+
+    if (!JS_GetProperty(cx, global, "IterableIterator", &constructor_val)) return false;
+    if (!constructor_val.isObject()) {
+      JS_ReportErrorASCII(cx, "IterableIterator is not a constructor");
+      return false;
+    }
+  }
+  JS::RootedObject constructor(cx, &constructor_val.toObject());
+
+  JS::RootedObject obj(cx);
+  if (!JS::Construct(cx, constructor_val, JS::HandleValueArray::empty(), &obj)) return false;
+  if (!obj) return false;
+
+  JS::SetReservedSlot(obj, IterableIteratorSlotIterableObject, JS::PrivateValue((void *)self));
+
+  args.rval().setObject(*obj);
+  return true;
+}
+
 bool PyIterableProxyHandler::getOwnPropertyDescriptor(
   JSContext *cx, JS::HandleObject proxy, JS::HandleId id,
   JS::MutableHandle<mozilla::Maybe<JS::PropertyDescriptor>> desc
 ) const {
+
+  // see if we're calling a function
   if (id.isString()) {
     for (size_t index = 0;; index++) {
       bool isThatFunction;
@@ -92,6 +223,24 @@ bool PyIterableProxyHandler::getOwnPropertyDescriptor(
     }
   }
 
+  // symbol property
+  if (id.isSymbol()) {
+    JS::RootedSymbol rootedSymbol(cx, id.toSymbol());
+
+    if (JS::GetSymbolCode(rootedSymbol) == JS::SymbolCode::iterator) {
+      JSFunction *newFunction = JS_NewFunction(cx, iterable_values, 0, 0, NULL);
+      if (!newFunction) return false;
+      JS::RootedObject funObj(cx, JS_GetFunctionObject(newFunction));
+      desc.set(mozilla::Some(
+        JS::PropertyDescriptor::Data(
+          JS::ObjectValue(*funObj),
+          {JS::PropertyAttribute::Enumerable}
+        )
+      ));
+      return true;
+    }
+  }
+
   PyObject *attrName = idToKey(cx, id);
   PyObject *self = JS::GetMaybePtrFromReservedSlot<PyObject>(proxy, PyObjectSlot);
   PyObject *item = PyDict_GetItemWithError(self, attrName);

tests/python/test_arrays.py

@@ -2204,4 +2204,11 @@ def test_iter_reentrace_next():
         third = next(result[0])          
         assert (False)
     except StopIteration as e:    
-        assert (True)  
+        assert (True)  
+
+def test_iter_for_of():
+    myit = iter((1,2))
+    result = [None, None]
+    pm.eval("""(result, myit) => {let index = 0; for (const value of myit) {result[index++] = value}}""")(result, myit)
+    assert result[0] == 1.0
+    assert result[1] == 2.0