mirror of https://github.com/python/cpython
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
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@ -1302,6 +1302,27 @@ class ChannelTests(TestBase):
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with self.assertRaises(interpreters.ChannelEmptyError):
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interpreters.channel_recv(cid)
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def test_recv_default(self):
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default = object()
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cid = interpreters.channel_create()
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obj1 = interpreters.channel_recv(cid, default)
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interpreters.channel_send(cid, None)
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interpreters.channel_send(cid, 1)
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interpreters.channel_send(cid, b'spam')
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interpreters.channel_send(cid, b'eggs')
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obj2 = interpreters.channel_recv(cid, default)
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obj3 = interpreters.channel_recv(cid, default)
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obj4 = interpreters.channel_recv(cid)
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obj5 = interpreters.channel_recv(cid, default)
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obj6 = interpreters.channel_recv(cid, default)
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self.assertIs(obj1, default)
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self.assertIs(obj2, None)
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self.assertEqual(obj3, 1)
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self.assertEqual(obj4, b'spam')
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self.assertEqual(obj5, b'eggs')
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self.assertIs(obj6, default)
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def test_run_string_arg_unresolved(self):
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cid = interpreters.channel_create()
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interp = interpreters.create()
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@ -1350,19 +1350,16 @@ _channel_recv(_channels *channels, int64_t id)
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_PyCrossInterpreterData *data = _channel_next(chan, PyInterpreterState_GetID(interp));
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PyThread_release_lock(mutex);
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if (data == NULL) {
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if (!PyErr_Occurred()) {
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PyErr_Format(ChannelEmptyError, "channel %" PRId64 " is empty", id);
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}
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return NULL;
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}
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// Convert the data back to an object.
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PyObject *obj = _PyCrossInterpreterData_NewObject(data);
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_PyCrossInterpreterData_Release(data);
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PyMem_Free(data);
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if (obj == NULL) {
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return NULL;
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}
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_PyCrossInterpreterData_Release(data);
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PyMem_Free(data);
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return obj;
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}
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@ -2351,20 +2348,37 @@ Add the object's data to the channel's queue.");
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static PyObject *
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channel_recv(PyObject *self, PyObject *args, PyObject *kwds)
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{
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static char *kwlist[] = {"cid", NULL};
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static char *kwlist[] = {"cid", "default", NULL};
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int64_t cid;
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if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&:channel_recv", kwlist,
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channel_id_converter, &cid)) {
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PyObject *dflt = NULL;
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if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&|O:channel_recv", kwlist,
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channel_id_converter, &cid, &dflt)) {
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return NULL;
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}
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Py_XINCREF(dflt);
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return _channel_recv(&_globals.channels, cid);
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PyObject *obj = _channel_recv(&_globals.channels, cid);
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if (obj != NULL) {
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Py_XDECREF(dflt);
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return obj;
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} else if (PyErr_Occurred()) {
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Py_XDECREF(dflt);
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return NULL;
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} else if (dflt != NULL) {
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return dflt;
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} else {
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PyErr_Format(ChannelEmptyError, "channel %" PRId64 " is empty", cid);
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return NULL;
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}
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}
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PyDoc_STRVAR(channel_recv_doc,
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"channel_recv(cid) -> obj\n\
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"channel_recv(cid, [default]) -> obj\n\
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\n\
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Return a new object from the data at the from of the channel's queue.");
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Return a new object from the data at the front of the channel's queue.\n\
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\n\
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If there is nothing to receive then raise ChannelEmptyError, unless\n\
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a default value is provided. In that case return it.");
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static PyObject *
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channel_close(PyObject *self, PyObject *args, PyObject *kwds)
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