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Support stopping propagation of events (#622)
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@ -121,6 +121,33 @@ random number, while if you say ``'eval 4+4'``, you will reply with the
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solution. Try it!
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Stopping propagation of Updates
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*******************************
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There might be cases when an event handler is supposed to be used solitary and
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it makes no sense to process any other handlers in the chain. For this case,
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it is possible to raise a ``StopPropagation`` exception which will cause the
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propagation of the update through your handlers to stop:
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.. code-block:: python
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from telethon.events import StopPropagation
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@client.on(events.NewMessage)
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def _(event):
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# ... some conditions
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event.delete()
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# Other handlers won't have an event to work with
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raise StopPropagation
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@client.on(events.NewMessage)
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def _(event):
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# Will never be reached, because it is the second handler
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# in the chain.
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pass
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Events module
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*************
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@ -873,3 +873,26 @@ class MessageChanged(_EventBuilder):
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self.edited = bool(edit_msg)
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self.deleted = bool(deleted_ids)
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self.deleted_ids = deleted_ids or []
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class StopPropagation(Exception):
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"""
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If this Exception is found to be raised in any of the handlers for a
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given update, it will stop the execution of all other registered
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event handlers in the chain.
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Think of it like a ``StopIteration`` exception in a for loop.
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Example usage:
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```
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@client.on(events.NewMessage)
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def delete(event):
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event.delete()
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# Other handlers won't have an event to work with
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raise StopPropagation
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@client.on(events.NewMessage)
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def _(event):
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# Will never be reached, because it is the second handler in the chain.
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pass
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```
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"""
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@ -1885,7 +1885,15 @@ class TelegramClient(TelegramBareClient):
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event = builder.build(update)
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if event:
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event._client = self
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try:
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callback(event)
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except events.StopPropagation:
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__log__.debug(
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"Event handler '{}' stopped chain of "
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"propagation for event {}."
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.format(callback.__name__, type(event).__name__)
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)
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break
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def add_event_handler(self, callback, event=None):
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"""
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