displayName is set after observer, observer could use a proxy to fetch it

[natew]

Since we write it as:

const Item = observer(() => <div />)
Item.displayName = 'Item'

It won't pick up the displayName. Perhaps observer could use a proxy to pick that up:

function observer(a) {
  return new Proxy(a, { set() { /* pick up displayName and apply it to reaction here */ } })
}

Not sure if Mobx accepts it "after its created" so to speak, but for now I just see a ton of observer() in my reaction logs which isn't very helpful.

[danielkcz]

Yea, I noticed that as well and it's a kinda main reason why I am mostly using useObserver whenever I can. In other cases, I just have a named function.

export default observer(function Item() {
  return <div />
})

Either way, these are just workarounds for sure. Personally, I haven't use Proxy for anything yet. There is an obvious problem it's not supported in IE11 so it would need some ponyfill. And it shouldn't be used in a production code.

Um, could you try to make some preliminary PR? Ideally with tests. I am definitely preoccupied for next weeks.

[xaviergonz]

There's always defineProperty with a getter and setter, which is like the poor's man proxy

[xaviergonz]

Either way though, since Reaction takes a plain string any name change after the fact would require a reaction destruction and re-creation, so maybe it could be added as an option to observer instead (displayName?: string)?

const Item = observer(() => <div />, { displayName: "Item" })

[danielkcz]

That's a really ugly escape hatch :) I would rather avoid things that cannot be compiled away from a production build. I cannot help it but using named function instead of anonymous one comes to be as the best solution really.

[danielkcz]

Another approach I just spotted in some chatroom. This way the observer grabs the name correctly.

const Item = () => <div />

export default observer(Item)

I've decided to reconsider this whole thing. It's not really a bug. It's coming from the way JS works. Some sufficient approaches have been described, for now, so I am closing.