core: support Receiver.get(thread_dead=False)

For tests.

mitogen/core.py

@@ -441,10 +441,10 @@ class Receiver(object):
     def empty(self):
         return self._latch.empty()
 
-    def get(self, timeout=None, block=True):
+    def get(self, timeout=None, block=True, throw_dead=True):
         _vv and IOLOG.debug('%r.get(timeout=%r, block=%r)', self, timeout, block)
         msg = self._latch.get(timeout=timeout, block=block)
-        if msg.is_dead:
+        if msg.is_dead and throw_dead:
             if msg.src_id == mitogen.context_id:
                 raise ChannelError(ChannelError.local_msg)
             else:

tests/router_test.py

@@ -223,40 +223,50 @@ class NoRouteTest(testlib.RouterMixin, testlib.TestCase):
         # Verify sending a message to an invalid handle yields a dead message
         # from the target context.
         l1 = self.router.fork()
+        recv = l1.send_async(mitogen.core.Message(handle=999))
+        msg = recv.get(throw_dead=False)
+        self.assertEquals(msg.is_dead, True)
+        self.assertEquals(msg.src_id, l1.context_id)
+
         recv = l1.send_async(mitogen.core.Message(handle=999))
         e = self.assertRaises(mitogen.core.ChannelError,
-            lambda: recv.get()
-        )
+                              lambda: recv.get())
         self.assertEquals(e.args[0], mitogen.core.ChannelError.remote_msg)
 
     def test_totally_invalid_context_returns_dead(self):
         recv = mitogen.core.Receiver(self.router)
-        self.router.route(
-            mitogen.core.Message(
+        msg = mitogen.core.Message(
             dst_id=1234,
             handle=1234,
             reply_to=recv.handle,
         )
-        )
+        self.router.route(msg)
+        rmsg = recv.get(throw_dead=False)
+        self.assertEquals(rmsg.is_dead, True)
+        self.assertEquals(rmsg.src_id, mitogen.context_id)
+
+        self.router.route(msg)
         e = self.assertRaises(mitogen.core.ChannelError,
-            lambda: recv.get()
-        )
+                              lambda: recv.get())
         self.assertEquals(e.args[0], mitogen.core.ChannelError.local_msg)
 
     def test_previously_alive_context_returns_dead(self):
         l1 = self.router.fork()
         l1.shutdown(wait=True)
         recv = mitogen.core.Receiver(self.router)
-        self.router.route(
-            mitogen.core.Message(
+        msg = mitogen.core.Message(
             dst_id=l1.context_id,
             handle=mitogen.core.CALL_FUNCTION,
             reply_to=recv.handle,
         )
-        )
+        self.router.route(msg)
+        rmsg = recv.get(throw_dead=False)
+        self.assertEquals(rmsg.is_dead, True)
+        self.assertEquals(rmsg.src_id, mitogen.context_id)
+
+        self.router.route(msg)
         e = self.assertRaises(mitogen.core.ChannelError,
-            lambda: recv.get()
-        )
+                              lambda: recv.get())
         self.assertEquals(e.args[0], mitogen.core.ChannelError.local_msg)