Py_INCREF/Py_DECREF when bridging coro task to python future and fix typo

Summary:
1. Py_INCREF when holding py future object in bridge function. Py_DECREF in a scope guard.
2. fix typo("folly::coroTask" should be "folly::coro::Task")

Reviewed By: yfeldblum, andriigrynenko

Differential Revision: D16341866

fbshipit-source-id: 1d5b946596cd86c4a949e2c66f007a6140046506

folly/python/coro.h

@@ -14,7 +14,7 @@
  * limitations under the License.
  */
 /*
- *  This file serves as a helper for bridging folly::coroTask and python
+ *  This file serves as a helper for bridging folly::coro::Task and python
  *  asyncio.future.
  */
 
@@ -40,9 +40,13 @@ void bridgeCoroTask(
     folly::coro::Task<T>&& coroFrom,
     folly::Function<void(folly::Try<T>&&, PyObject*)> callback,
     PyObject* userData) {
+  // We are handing over a pointer to a python object to c++ and need
+  // to make sure it isn't removed by python in that time.
+  Py_INCREF(userData);
+  auto guard = folly::makeGuard([=] { Py_DECREF(userData); });
   std::move(coroFrom).scheduleOn(executor).start(
-      [callback = std::move(callback),
-       userData](folly::Try<T>&& result) mutable {
+      [callback = std::move(callback), userData, guard = std::move(guard)](
+          folly::Try<T>&& result) mutable {
         callback(std::move(result), userData);
       });
 }

folly/python/coro.pxd

@@ -16,7 +16,7 @@ from cpython.ref cimport PyObject
 from folly cimport cFollyExecutor, cFollyTry
 
 cdef extern from "folly/experimental/coro/Task.h" namespace "folly::coro" nogil:
-    cdef cppclass cFollyCoroTask "folly::coroTask"[T]:
+    cdef cppclass cFollyCoroTask "folly::coro::Task"[T]:
         pass
 
 cdef extern from "folly/python/coro.h" namespace "folly::python":