[Python-checkins] bpo-29922: Improve error messages in 'async with' (GH-6352)

Mon Apr 2 18:41:48 EDT 2018

https://github.com/python/cpython/commit/a68f2f0578bbf812fa2264d0e0bb388340d6e230
commit: a68f2f0578bbf812fa2264d0e0bb388340d6e230
branch: master
author: Serhiy Storchaka <storchaka at gmail.com>
committer: GitHub <noreply at github.com>
date: 2018年04月03日T01:41:38+03:00
summary:
bpo-29922: Improve error messages in 'async with' (GH-6352)
when __aenter__() or __aexit__() return non-awaitable object.
files:
A Misc/NEWS.d/next/Core and Builtins/2018-04-03-00-30-25.bpo-29922.CdLuMl.rst
M Lib/test/test_coroutines.py
M Python/ceval.c

diff --git a/Lib/test/test_coroutines.py b/Lib/test/test_coroutines.py
index fe26199f95af..9ad7ff9564bc 100644
--- a/Lib/test/test_coroutines.py
+++ b/Lib/test/test_coroutines.py
@@ -1255,7 +1255,9 @@ def __aexit__(self, *e):
 pass
 
 with self.assertRaisesRegex(
- TypeError, "object int can't be used in 'await' expression"):
+ TypeError,
+ "'async with' received an object from __aenter__ "
+ "that does not implement __await__: int"):
 # it's important that __aexit__ wasn't called
 run_async(foo())
 
@@ -1275,7 +1277,9 @@ def __aexit__(self, *e):
 run_async(foo())
 except TypeError as exc:
 self.assertRegex(
- exc.args[0], "object int can't be used in 'await' expression")
+ exc.args[0],
+ "'async with' received an object from __aexit__ "
+ "that does not implement __await__: int")
 self.assertTrue(exc.__context__ is not None)
 self.assertTrue(isinstance(exc.__context__, ZeroDivisionError))
 else:
@@ -1299,8 +1303,9 @@ def __aexit__(self, *e):
 
 
 with self.assertRaisesRegex(
- TypeError, "object int can't be used in 'await' expression"):
-
+ TypeError,
+ "'async with' received an object from __aexit__ "
+ "that does not implement __await__: int"):
 run_async(foo())
 
 self.assertEqual(CNT, 1)
diff --git a/Misc/NEWS.d/next/Core and Builtins/2018-04-03-00-30-25.bpo-29922.CdLuMl.rst b/Misc/NEWS.d/next/Core and Builtins/2018-04-03-00-30-25.bpo-29922.CdLuMl.rst
new file mode 100644
index 000000000000..d8c144e59d6c
--- /dev/null
+++ b/Misc/NEWS.d/next/Core and Builtins/2018-04-03-00-30-25.bpo-29922.CdLuMl.rst	
@@ -0,0 +1,2 @@
+Improved error messages in 'async with' when ``__aenter__()`` or
+``__aexit__()`` return non-awaitable object.
diff --git a/Python/ceval.c b/Python/ceval.c
index d18a284e9f9d..da83e41f5ddd 100644
--- a/Python/ceval.c
+++ b/Python/ceval.c
@@ -69,6 +69,7 @@ static PyObject * unicode_concatenate(PyObject *, PyObject *,
 static PyObject * special_lookup(PyObject *, _Py_Identifier *);
 static int check_args_iterable(PyObject *func, PyObject *vararg);
 static void format_kwargs_mapping_error(PyObject *func, PyObject *kwargs);
+static void format_awaitable_error(PyTypeObject *, int);
 
 #define NAME_ERROR_MSG \
 "name '%.200s' is not defined"
@@ -1736,6 +1737,11 @@ _PyEval_EvalFrameDefault(PyFrameObject *f, int throwflag)
 PyObject *iterable = TOP();
 PyObject *iter = _PyCoro_GetAwaitableIter(iterable);
 
+ if (iter == NULL) {
+ format_awaitable_error(Py_TYPE(iterable),
+ _Py_OPCODE(next_instr[-2]));
+ }
+
 Py_DECREF(iterable);
 
 if (iter != NULL && PyCoro_CheckExact(iter)) {
@@ -4985,6 +4991,25 @@ format_exc_unbound(PyCodeObject *co, int oparg)
 }
 }
 
+static void
+format_awaitable_error(PyTypeObject *type, int prevopcode)
+{
+ if (type->tp_as_async == NULL || type->tp_as_async->am_await == NULL) {
+ if (prevopcode == BEFORE_ASYNC_WITH) {
+ PyErr_Format(PyExc_TypeError,
+ "'async with' received an object from __aenter__ "
+ "that does not implement __await__: %.100s",
+ type->tp_name);
+ }
+ else if (prevopcode == WITH_CLEANUP_START) {
+ PyErr_Format(PyExc_TypeError,
+ "'async with' received an object from __aexit__ "
+ "that does not implement __await__: %.100s",
+ type->tp_name);
+ }
+ }
+}
+
 static PyObject *
 unicode_concatenate(PyObject *v, PyObject *w,
 PyFrameObject *f, const _Py_CODEUNIT *next_instr)
