Sync serial, clean recv. (pymodbus-dev#1340)

Author: janiversen

pymodbus/client/serial.py

@@ -336,8 +336,8 @@ def recv(self, size):
             )
         if size is None:
             size = self._wait_for_data()
-        elif size > self._in_waiting():
-            self._wait_for_data()
+        if size > self._in_waiting():
+            size = self._wait_for_data()
         result = self.socket.read(size)
         return result
 

test/test_client_sync.py

@@ -388,7 +388,7 @@ def test_basic_sync_serial_client(self, mock_serial):
         self.assertEqual(0, client.send(None))
         client.state = 0
         self.assertEqual(1, client.send(b"\x00"))
-        self.assertEqual(b"\x00", client.recv(1))
+        self.assertEqual(b"", client.recv(1))
 
         # connect/disconnect
         self.assertTrue(client.connect())