Uncaught Error: Component's "only-when-overflow" property should be a function, but got [boolean] instead

[Unluckynerd]

• Check if updating to the latest Preact version resolves the issue

Describe the bug

I'm using a custom web component called my-tooltip and there's a boolean attribute called only-when-overflow.When using the only-when-overflow attribute i'm getting the below error.

Uncaught Error: Component's "only-when-overflow" property should be a function, but got [boolean] instead
<my-tooltip only-when-overflow="true" for="a1a1">..</my-tooltip>

To Reproduce

We usually use a attribute which starts with on to handle events eg: onClick, onKeyPress which requires function. Here I'm using a boolean attribute which starts with on and the error thrown

[JoviDeCroock]

Gotcha, this is caused by our function check here instead we could check whether the third character is an uppercase-letter by doing name[3] === name[3].toUpperCase() or check whether either the old or new value is a function 😅

[marvinhagemeister]

@JoviDeCroock Wondering if we could limit the warning only to native HTML elements. Like check only do the check if the element name doesn't have a - character in the name.

[JoviDeCroock]

@marvinhagemeister something like this https://github.com/preactjs/preact/compare/custom-element-func-safety?expand=1

[marvinhagemeister]

Ohh I mistakenly thought it would only affect the debug check. Doing .indexOf everytime could be a bit expensive. The uppercase check won't be reliable enough either as Preact also allows lowercase events despite those not being included in the typings I think.

I'm not sure what the best path forward is. It's really unfortunate that custom elements don't seem to give you a way to check what properties they expose.

[JoviDeCroock]

@marvinhagemeister a cheaper alternative would be https://github.com/preactjs/preact/compare/custom-element-func-safety-2?expand=1