Use is_published correctly (#912)

Fix an issue in the MQTT client where is was using is_published as if it was a bool instead of a function.

tavern/_plugins/mqtt/client.py

@@ -376,7 +376,9 @@ def message_received(self, topic: str, timeout: int = 1):
 
         return msg
 
-    def publish(self, topic, payload=None, qos=None, retain=None):
+    def publish(
+        self, topic: str, payload=None, qos=None, retain=None
+    ) -> paho.MQTTMessageInfo:
         """publish message using paho library"""
         self._wait_for_subscriptions()
 
@@ -389,7 +391,14 @@ def publish(self, topic, payload=None, qos=None, retain=None):
             kwargs["retain"] = retain
         msg = self._client.publish(topic, payload, **kwargs)
 
-        if not msg.is_published:
+        # Wait for 2*connect timeout which should be plenty to publish the message even with qos 2
+        # TODO: configurable
+        try:
+            msg.wait_for_publish(self._connect_timeout * 2)
+        except (RuntimeError, ValueError) as e:
+            raise exceptions.MQTTError("could not publish message") from e
+
+        if not msg.is_published():
             raise exceptions.MQTTError(
                 "err {:s}: {:s}".format(
                     _err_vals.get(msg.rc, "unknown"), paho.error_string(msg.rc)

tests/unit/test_mqtt.py

@@ -1,3 +1,4 @@
+import time
 from typing import Dict
 from unittest.mock import MagicMock, Mock, patch
 
@@ -71,28 +72,67 @@ def test_context_connection_success(self, fake_client):
             with fake_client as x:
                 assert fake_client == x
 
-    def test_assert_message_published(self, fake_client):
-        """If it couldn't immediately publish the message, error out"""
+    def test_assert_message_published_error(self, fake_client):
+        """Error waiting for it to publish"""
+
+        class FakeMessage(paho.MQTTMessageInfo):
+            def wait_for_publish(self, timeout=None):
+                raise RuntimeError
+
+            rc = 1
+
+        with patch.object(fake_client._client, "subscribe"), patch.object(
+            fake_client._client, "publish", return_value=FakeMessage(10)
+        ):
+            with pytest.raises(exceptions.MQTTError):
+                fake_client.publish("abc", "123")
+
+    def test_assert_message_published_failure(self, fake_client):
+        """If it couldn't publish the message, error out"""
+
+        class FakeMessage(paho.MQTTMessageInfo):
+            def wait_for_publish(self, timeout=None):
+                return
+
+            def is_published(self):
+                return False
 
-        class FakeMessage:
-            is_published = False
             rc = 1
 
         with patch.object(fake_client._client, "subscribe"), patch.object(
-            fake_client._client, "publish", return_value=FakeMessage()
+            fake_client._client, "publish", return_value=FakeMessage(10)
         ):
             with pytest.raises(exceptions.MQTTError):
                 fake_client.publish("abc", "123")
 
+    def test_assert_message_published_delay(self, fake_client):
+        """Published but only after a small delay"""
+
+        class FakeMessage(paho.MQTTMessageInfo):
+            def wait_for_publish(self, timeout=None):
+                time.sleep(0.5)
+
+            def is_published(self):
+                return True
+
+            rc = 1
+
+        with patch.object(fake_client._client, "subscribe"), patch.object(
+            fake_client._client, "publish", return_value=FakeMessage(10)
+        ):
+            fake_client.publish("abc", "123")
+
     def test_assert_message_published_unknown_err(self, fake_client):
         """Same, but with an unknown error code"""
 
-        class FakeMessage:
-            is_published = False
+        class FakeMessage(paho.MQTTMessageInfo):
+            def is_published(self):
+                return False
+
             rc = 2342423
 
         with patch.object(fake_client._client, "subscribe"), patch.object(
-            fake_client._client, "publish", return_value=FakeMessage()
+            fake_client._client, "publish", return_value=FakeMessage(10)
         ):
             with pytest.raises(exceptions.MQTTError):
                 fake_client.publish("abc", "123")