feat(runtime-core): improve render context warning

[LinusBorg]

Problem

When we try to access a non-existing property on a component during rendering, we get this helpful warning:

Property ${JSON.stringify(key)} was accessed during render but is not defined on instance.

However, the current implementation logs this warning as long as some component is currently rendering. In other words, the warning is not limited to the render cycle of the component instance that we tried to read the property from.

Solution

I think this warning should only be printed out during the component's own render.

Use case:

When reading a property from a child component instance obtained from a template ref, one might not know which kind of component the ref contains, so reading a prop in order to do a sort of duck typing is useful.

But with the current implementation, a warning would be logged to the console each time a child component is checked programmatically like this.

[github-actions]

Size report

Path	Size
vue.global.prod.js	40.15 KB (0%)
runtime-dom.global.prod.js	26.43 KB (0%)
size-check.global.prod.js	15.95 KB (0%)