Reset line numbers if printer sends "start" when operational

Might have been an external reset of the printer we didn't otherwise
detect, and unless we reset the line numbers we'll now be off and run
into resend requests.

Solves #1676

src/octoprint/plugins/virtual_printer/virtual.py

@@ -25,7 +25,8 @@ class VirtualPrinter(object):
 	sleep_after_regex = re.compile("sleep_after ([GMTF]\d+) (\d+)")
 	sleep_after_next_regex = re.compile("sleep_after_next ([GMTF]\d+) (\d+)")
 	custom_action_regex = re.compile("action_custom ([a-zA-Z0-9_]+)(\s+.*)?")
-	prepare_ok_regex = re.compile("prepare_ok (.*)?")
+	prepare_ok_regex = re.compile("prepare_ok (.*)")
+	send_regex = re.compile("send (.*)")
 
 	def __init__(self, seriallog_handler=None, read_timeout=5.0, write_timeout=10.0):
 		import logging
@@ -560,6 +561,11 @@ class VirtualPrinter(object):
 			| Sleeps <seconds> s after each execution of <command>
 			sleep_after_next <str:command> <int:seconds>
 			| Sleeps <seconds> s after execution of next <command>
+
+			# Misc
+
+			send <str:message>
+			| Sends back <message>
 			"""
 			for line in usage.split("\n"):
 				self._send("echo: {}".format(line.strip()))
@@ -589,6 +595,7 @@ class VirtualPrinter(object):
 				sleep_after_next_match = VirtualPrinter.sleep_after_next_regex.match(data)
 				custom_action_match = VirtualPrinter.custom_action_regex.match(data)
 				prepare_ok_match = VirtualPrinter.prepare_ok_regex.match(data)
+				send_match = VirtualPrinter.send_regex.match(data)
 
 				if sleep_match is not None:
 					interval = int(sleep_match.group(1))
@@ -612,6 +619,8 @@ class VirtualPrinter(object):
 				elif prepare_ok_match is not None:
 					ok = prepare_ok_match.group(1)
 					self._prepared_oks.append(ok)
+				elif send_match is not None:
+					self._send(send_match.group(1))
 			except:
 				pass
 

src/octoprint/util/comm.py

@@ -1392,6 +1392,18 @@ class MachineCom(object):
 						self._log("There was a timeout while trying to connect to the printer")
 						self.close(wait=False)
 
+				### Operational (idle or busy)
+				elif self._state in (self.STATE_OPERATIONAL,
+				                     self.STATE_PRINTING,
+				                     self.STATE_PAUSED,
+				                     self.STATE_TRANSFERING_FILE):
+					if line == "start": # exact match, to be on the safe side
+						message = "Printer sent 'start' while already operational. External reset? " \
+						          "Resetting line numbers to be on the safe side"
+						self._log(message)
+						self._logger.warn(message)
+						self.resetLineNumbers()
+
 			except:
 				self._logger.exception("Something crashed inside the serial connection loop, please report this in OctoPrint's bug tracker:")