[User-friendliness] Event handler without the event parameter

[antocuni]

See the Tracking issue #904 for the context.

Original question on discord

The mistake it this:

async def fetch_data():
    ...
document.getElementById('btn-test').addEventListener('click', create_proxy(fetch_data))

The error is this:

Uncaught PythonError: TypeError: fetch_data() takes 0 positional arguments but 1 was given

One related issue/discussion is #835 .
This could be solved by providing, documenting and encouraging the use of a higher level API. For example:

@event('btn-test', 'click')
async def fetch_data():
    ...

In this case, the decorator would automatically call create_proxy and addEventListener, but most importantly it could also introspect the function signature and raise an user friendly error in case the actual signature doesn't match the expected one.

[Cheukting]

I like this suggestion. The original syntax is very JS-like (as it supposes to be) and for people who are not familiar with JS, this is an easy mistake to make. With the decorator, it can help to make it easier for beginners.

[tedpatrick]

+1 The @event decorator can also detect arguments support and optionally not pass the event.

[marimeireles]

This is being under dev here

[JeffersGlass]

After some discussion, this morphed into the @when decorator which was added in #1428 .