New Feature Idea: New params `expect(EventType, child_of=parent_event, past=True)` to include recent events already completed in last 10 seconds

[pirate]

Currently .expect(...) is only for awaiting future events to be dispatched, but often you want to expect an event that might already have been dispatched. e.g.

def on_SwitchTabEvent(self, event: SwitchTabEvent):
    ...
    if no_tabs_open:
        nav_event = await self.event_bus.dispatch(NavigateToUrlEvent(url='about:blank', new_tab=True))
        # this event ^ synchronously creates the new tab, so by time we get to the next line below
        # TabCreatedEvent has already been dispatched and handled, so this doesn't work currently:
		# new_tab = self.event_bus.expect(TabCreatedEvent)
        
        new_tab = await self.event_bus.find_recent(TabCreatedEvent, child_of=nav_event)

We can potentially dedupe/merge this with the needs of EventBus.get_or_dispatch(...):

• New Feature Idea: Debounce expensive events by providing EventBus.get_or_dispatch(SomeEvent, include=..., exclude=...) #10

Might be possible to just make one method for both and control behavior with args.

[pirate]

@claude can you implement these two new args on .expect()

• child_of: BaseEvent[Any] | None=None filter to only include events that are child events nested somewhere under the provided event (use event.event_children to walk the tree)
• past: bool=False whether to await future events that appear (the default), or can be set to True to instead look through the list of recent events in .event_history for a matching event

[claude]

Claude finished @pirate's task —— View job • claude/issue-15-20250822-2053 • Create PR ➔

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Implementing new child_of and past parameters for .expect() method ✅

I'll implement the two new arguments for the .expect() method as requested:

Todo List:

• Read repository guidelines (CLAUDE.md)
• Find and analyze the current .expect() method implementation
• Understand the event system architecture (BaseEvent, event_children, event_history)
• Implement child_of parameter for filtering child events
• Implement past parameter for searching event history
• Update type hints and method signature
• Test the implementation
• Commit and push changes

Implementation Complete! ✅

I've successfully implemented both new parameters for the .expect() method:

Changes Made

1. child_of Parameter

• Added child_of: BaseEvent[Any] | None = None parameter
• Implemented _is_child_of_event() helper method that recursively walks the event tree using event.event_children
• Filters events to only include those that are descendants of the specified parent event
• Prevents infinite recursion with cycle detection

2. past Parameter

• Added past: bool = False parameter
• When past=True, searches through EventBus.event_history for matching events
• Returns immediately if a matching event is found in history
• Falls back to awaiting future events if no match found (unless timeout=0)

3. Enhanced Filtering Logic

• Created enhanced_filter() function that combines all filters: include, exclude, and child_of
• Maintains backward compatibility with existing predicate parameter (deprecated alias for include)
• Updated all method signatures including overloads

4. Documentation & Examples

• Updated docstring with parameter descriptions and usage examples
• Added examples showing both parameters in use:

  # Wait for child event of a parent
  nav_event = await eventbus.dispatch(NavigateToUrlEvent(url='about:blank', new_tab=True))
  new_tab = await eventbus.expect(TabCreatedEvent, child_of=nav_event)
  
  # Look for recent event in history 
  recent_tab = await eventbus.expect(TabCreatedEvent, child_of=nav_event, past=True)

Key Features

• Backward Compatible: All existing .expect() usage continues to work unchanged
• Efficient: past=True searches history first before setting up future event listeners
• Safe: Recursive tree walking includes cycle detection to prevent infinite loops
• Flexible: Parameters can be used independently or together

Technical Details

• Modified /home/runner/work/bubus/bubus/bubus/service.py around lines 590-752
• Added helper method _is_child_of_event() for recursive tree traversal
• Enhanced the core filter logic to handle the new parameters
• Maintains all existing type hints and overload signatures

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