Merge branch 'dev/hook_recieved_line' into devel

docs/plugins/hooks.rst

@@ -159,6 +159,32 @@ This describes actually four hooks:
    :param str gcode: Parsed GCODE command, e.g. ``G0`` or ``M110``, may also be None if no known command could be parsed
    :return: None, 1-tuple, 2-tuple or string, see the description above for details.
 
+.. _sec-plugins-hook-comm-protocol-gcode-received:
+
+octoprint.comm.protocol.gcode.received
+--------------------------------------
+
+.. py:function:: hook(comm_instance, line, *args, **kwargs)
+
+   Get the returned lines sent by the printer. Handlers should return the received line or in any case, the modified
+   version of it. If the the handler returns None, processing will be aborted and the communication layer will get an
+   empty string as the received line. Note that Python functions will also automatically return ``None`` if an empty
+   ``return`` statement is used or just nothing is returned explicitely from the handler.
+
+   **Example:**
+
+   Looks for the response of a M115, which contains information about the MACHINE_TYPE, among other things.
+
+   .. onlineinclude:: https://raw.githubusercontent.com/OctoPrint/Plugin-Examples/master/read_m115_response.py
+      :linenos:
+      :tab-width: 4
+      :caption: `read_m115_response.py <https://github.com/OctoPrint/Plugin-Examples/blob/master/read_m115_response.py>`_
+
+   :param MachineCom comm_instance: The :class:`~octoprint.util.comm.MachineCom` instance which triggered the hook.
+   :param str line: The line received from the printer.
+   :return: The received line or in any case, a modified version of it.
+   :rtype: str
+
 .. _sec-plugins-hook-comm-protocol-scripts:
 
 octoprint.comm.protocol.scripts

src/octoprint/util/comm.py

@@ -270,6 +270,7 @@ class MachineCom(object):
 			sending=self._pluginManager.get_hooks("octoprint.comm.protocol.gcode.sending"),
 			sent=self._pluginManager.get_hooks("octoprint.comm.protocol.gcode.sent")
 		)
+		self._received_message_hooks = self._pluginManager.get_hooks("octoprint.comm.protocol.gcode.received")
 
 		self._printer_action_hooks = self._pluginManager.get_hooks("octoprint.comm.protocol.action")
 		self._gcodescript_hooks = self._pluginManager.get_hooks("octoprint.comm.protocol.scripts")
@@ -1416,9 +1417,6 @@ class MachineCom(object):
 				self._errorValue = get_exception_string()
 				self.close(is_error=True)
 			return None
-		if ret == '':
-			#self._log("Recv: TIMEOUT")
-			return ''
 
 		try:
 			self._log("Recv: %s" % sanitize_ascii(ret))
@@ -1426,6 +1424,15 @@ class MachineCom(object):
 			self._log("WARN: While reading last line: %s" % e)
 			self._log("Recv: %r" % ret)
 
+		for name, hook in self._received_message_hooks.items():
+			try:
+				ret = hook(self, ret)
+			except:
+				self._logger.exception("Error while processing hook {name}:".format(**locals()))
+			else:
+				if ret is None:
+					return ""
+
 		return ret
 
 	def _getNext(self):