plugins TEXT-COMMANDS, XEP-0045, XEP-0048, XEP-0249:

- give a feedback instead of sending the message when the command is invalid or used in a wrong context
    - add command /join for XEP-0249

src/plugins/plugin_misc_text_commands.py

@@ -43,6 +43,8 @@ class TextCommands(object):
     #       plugins need a dynamic translation system (translation
     #       should be downloadable independently)
 
+    HELP_SUGGESTION = _("Type '/help' to get a list of the available commands. If you didn't want to use a command, please start your message with '//' to escape the slash.")
+
     def __init__(self, host):
         log.info(_("Text commands initialization"))
         self.host = host
@@ -133,9 +135,10 @@ class TextCommands(object):
                 d = defer.maybeDeferred(self._commands[command], mess_data, profile)
                 d.addCallback(retHandling)
             except KeyError:
-                pass
+                self.feedBack(_("Unknown command /%s. ") % command + self.HELP_SUGGESTION, mess_data, profile)
+                return Failure(MessageSentAndStored("text commands took over", mess_data))
 
-        return d or mess_data # if a command is detected, we should have a deferred, else be send the message normally
+        return d or mess_data  # if a command is detected, we should have a deferred, else we send the message normally
 
     def getRoomJID(self, arg, service_jid):
         """Return a room jid with a shortcut
@@ -159,6 +162,19 @@ class TextCommands(object):
 
         self.host.bridge.newMessage(unicode(mess_data["to"]), message, mess_data['type'], unicode(_from), {}, profile=profile)
 
+    def feedBackWrongContext(self, command, types, mess_data, profile):
+        """Give a generic message to the user when a command has been used in a wrong context.
+
+        @param command (string): the command name (without the slash)
+        @param types (string, list): the message types to which the command applies.
+        @param mess_data (dict): original message data
+        @param profile: %(doc_profile)s
+        """
+        if not isinstance(types, str):
+            types = _(' or ').join(types)
+        feedback = _("/%(command)s command only applies on %(type)s messages. ") % {'command': command, 'type': types}
+        self.host.plugins[C.TEXT_CMDS].feedBack(feedback + self.HELP_SUGGESTION, mess_data, profile)
+
     def cmd_whois(self, mess_data, profile):
         """show informations on entity"""
         log.debug("Catched whois command")