context parameter for @app.schedule lambdas

[xplorld]

Currently we do not provide context to @app.schedule lambdas. It may be useful in some cases when the user wants to know who I am and maybe check remaining times.
To be backward compatible, the ScheduledEventHandler.__call__ needs to check client code's signature to support 1-param version (event) and 2-param version (event, context) client code.

By the way, the event in @app.schedule is different from event in @app.lambda_function, which may arise confusion. Maybe we can rename the parameter name to things like schedule_event or cloudwatch_event?

[kyleknap]

Unfortunately, I do not think we would be able to expand the signature to include a context along with an event. However, the app object does expose a lambda_context property that you could access from with in the schedule event function. So something like this:

from chalice import Chalice
from chalice.app import Rate

app = Chalice(app_name='ping')


@app.schedule(Rate(1, Rate.MINUTES))
def index(event):
    print(app.lambda_context)
    return {'hello': 'world'}

The one thing I did notice though is that the ScheduledEventHandler does not set the lambda_context property to the context object that gets passed through right now, but we could update the code to set it. Would using app.lambda_context work for you? @jamesls do you have any thoughts on this?

As to renaming event to schedule_event, that is something you should be able to control in defining your function. We just use event in the examples by convention. Not sure if it is intentional (@jamesls would know more about this) but we pass the event in as a positional argument so the name you give the argument does not matter. If we switched to be passing it in as a keyword argument that would probably cause application to break and thus something we would avoid doing. So you should be safe there.

[jamesls]

do you have any thoughts on this?

The .lambda_context was needed because the args in a route() function's were controlled by the user, so we needed somewhere else to place the context.

Could we just add a context attribute to the event? Otherwise we need to have each event have a reference to the app object which I'd prefer to avoid.

[kyleknap]

I would be fine with that as well.

[xplorld]

It would be nice to add event.context.