bpo-32604: Add support for a "default" arg in channel_recv(). (GH-19770)

This allows the caller to avoid creation of an exception when the channel is empty (just like `dict.get()` works).  `ChannelEmptyError` is still raised if no default is provided.

Automerge-Triggered-By: @ericsnowcurrently
This commit is contained in:
Eric Snow 2020-04-28 17:11:32 -06:00 committed by GitHub
parent 6d86a2331e
commit 5e8c691594
No known key found for this signature in database
GPG Key ID: 4AEE18F83AFDEB23
2 changed files with 46 additions and 11 deletions

View File

@ -1302,6 +1302,27 @@ class ChannelTests(TestBase):
with self.assertRaises(interpreters.ChannelEmptyError):
interpreters.channel_recv(cid)
def test_recv_default(self):
default = object()
cid = interpreters.channel_create()
obj1 = interpreters.channel_recv(cid, default)
interpreters.channel_send(cid, None)
interpreters.channel_send(cid, 1)
interpreters.channel_send(cid, b'spam')
interpreters.channel_send(cid, b'eggs')
obj2 = interpreters.channel_recv(cid, default)
obj3 = interpreters.channel_recv(cid, default)
obj4 = interpreters.channel_recv(cid)
obj5 = interpreters.channel_recv(cid, default)
obj6 = interpreters.channel_recv(cid, default)
self.assertIs(obj1, default)
self.assertIs(obj2, None)
self.assertEqual(obj3, 1)
self.assertEqual(obj4, b'spam')
self.assertEqual(obj5, b'eggs')
self.assertIs(obj6, default)
def test_run_string_arg_unresolved(self):
cid = interpreters.channel_create()
interp = interpreters.create()

View File

@ -1350,19 +1350,16 @@ _channel_recv(_channels *channels, int64_t id)
_PyCrossInterpreterData *data = _channel_next(chan, PyInterpreterState_GetID(interp));
PyThread_release_lock(mutex);
if (data == NULL) {
if (!PyErr_Occurred()) {
PyErr_Format(ChannelEmptyError, "channel %" PRId64 " is empty", id);
}
return NULL;
}
// Convert the data back to an object.
PyObject *obj = _PyCrossInterpreterData_NewObject(data);
_PyCrossInterpreterData_Release(data);
PyMem_Free(data);
if (obj == NULL) {
return NULL;
}
_PyCrossInterpreterData_Release(data);
PyMem_Free(data);
return obj;
}
@ -2351,20 +2348,37 @@ Add the object's data to the channel's queue.");
static PyObject *
channel_recv(PyObject *self, PyObject *args, PyObject *kwds)
{
static char *kwlist[] = {"cid", NULL};
static char *kwlist[] = {"cid", "default", NULL};
int64_t cid;
if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&:channel_recv", kwlist,
channel_id_converter, &cid)) {
PyObject *dflt = NULL;
if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&|O:channel_recv", kwlist,
channel_id_converter, &cid, &dflt)) {
return NULL;
}
Py_XINCREF(dflt);
return _channel_recv(&_globals.channels, cid);
PyObject *obj = _channel_recv(&_globals.channels, cid);
if (obj != NULL) {
Py_XDECREF(dflt);
return obj;
} else if (PyErr_Occurred()) {
Py_XDECREF(dflt);
return NULL;
} else if (dflt != NULL) {
return dflt;
} else {
PyErr_Format(ChannelEmptyError, "channel %" PRId64 " is empty", cid);
return NULL;
}
}
PyDoc_STRVAR(channel_recv_doc,
"channel_recv(cid) -> obj\n\
"channel_recv(cid, [default]) -> obj\n\
\n\
Return a new object from the data at the from of the channel's queue.");
Return a new object from the data at the front of the channel's queue.\n\
\n\
If there is nothing to receive then raise ChannelEmptyError, unless\n\
a default value is provided. In that case return it.");
static PyObject *
channel_close(PyObject *self, PyObject *args, PyObject *kwds)