Middleware logic in turncontext emit is broken

[heyitsaamir]

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Version

4.16.2

Describe the bug

The turncontext middlware chain is as follows:

botbuilder-python/libraries/botbuilder-core/botbuilder/core/turn_context.py

Lines 287 to 304 in a7f5d91

	handlers = copy(plugins)
	async def emit_next(i: int):
	context = self
	try:
	if i < len(handlers):
	async def next_handler():
	await emit_next(i + 1)
	await handlers[i](context, arg, next_handler)
	except Exception as error:
	raise error
	await emit_next(0)
	# logic does not use parentheses because it's a coroutine
	return await logic

Notice how the "logic" runs after all the middlware has run? This prevents any middlware from awaiting the result of the "next" middleware. This means that if you wanted to wait for the "response" from the last middleware (which runs the actual logic to send the activity), you can't.

This is in contrast with how the middleware for js is built:
https://github.com/microsoft/botbuilder-js/blob/3b8fcab21a0a5434706da8eace17117722ffd78b/libraries/botbuilder-core/src/turnContext.ts#L864.

Here, if you wanted to do:

async function MyMiddleware(context, args, next) {
   console.log(args)
   const res = await next()
   console.log(res)
}

you can. But in python, the same thing would not be possible because the handlers don't wait for the last handler (which is the actual logic) to be run in the same chain as all the handlers.