Feature Request: Allow nullish values to omit event handlers

[brandonmcconnell]

Describe the problem

Most props can be excluded in this sort of fashion:

<MyComponent
  prop={condition ? someValue : undefined}
/>

However, this does not work for event handlers (at least in TS setups) due to the expected TypeScript type (e: MouseEvent) => any.

Describe the proposed solution

I propose setting up event handlers in such a way that they support the types null | undefined as well as (e: MouseEvent) => any and that in the case of null | undefined, the handler be excluded from the element/component instance.

Alternatives considered

Currently, to work around this, I am using an "empty" function with nullish coalescing. This won't kill site performance by any means, but firing a pointless function like this is not the ideal workaround.

Here is an example of my current setup:

<MyComponent
  prop={condition ? someValue : undefined}
  on:click={clickFunction ?? (() => {})}
/>

Importance

would make my life easier

[Conduitry]

@dummdidumm I think this would be a language-tools thing? Is that correct? The compiler itself already allows nullish values for event handlers, and treats them as not attaching a handler.

[dummdidumm]

Yes this needs a adjustment in language tools. This is already allowed for Dom events but not component events

[brandonmcconnell]

Thanks, @Conduitry and @dummdidumm!

[dummdidumm]

@Conduitry was about to implement this and tested it out in the REPL one more time, and noticed that this isn't implemented for component events. If I do <Component on:click={null} />, an error is thrown every time I fire the click event. The "handles null/undefined" behavior seems to be implements for DOM events only.

[Conduitry]

This should be supported now as of 3.51.0.

[maxlath]

Is there a way to re-enable the strict mode? ^^'