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

1 files changed, 21 insertions, 0 deletions

diff --git a/Lib/test/test__xxsubinterpreters.py b/Lib/test/test__xxsubinterpreters.py
index 30f8f98..8a368dc 100644
--- a/Lib/test/test__xxsubinterpreters.py
+++ b/Lib/test/test__xxsubinterpreters.py
@@ -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()