overlay should be injected into the page only once

[yyx990803]

Currently with a multi-entry setup, every entry's hot client will inject a copy of the overlay on to the page. When a compilation error is thrown, it will be sent to all these overlays regardless of which entry chunk it was associated with, therefore there will be multiple overlays open at the same time.

This PR simply ensures there will be only one overlay injected at a time.

[glenjamin]

I think I'd rather do this using an ID attribute on the created overlay element - so the logic is nicely contained inside the client overlay file.

It might also be worth making the overlay element creation lazy, so we're not adding an element unless there's an error.

[yyx990803]

Making it lazy would conflict with the ID attribute approach though, because when the clients are evaluated on load there would be no overlay injected, so there's no way to check for that ID.

[yyx990803]

Oh I see you mean checking for the id before appending...

[yyx990803]

Hmm, the issue is not only about the overlay - it's the problems function being called more than necessary. With multiple entries there will also be duplicate warnings in the console.

[yyx990803]

So, to clarify it a bit: for multiple clients on the same page, each client should call its own processUpdate function, because only that client has access to the modules in the same chunk; but only one client should respond to the problems and success, because the errors are sent to every client regardless of which chunk they are associated with.

[glenjamin]

Ah, I see. The problems reporting needs to be a singleton on the page.

Is it possible to tie the errors to the bundles they're related to? The messages that come over the socket contain the bundle name & hash. I've never used multiple bundles, so I'm not clear how that part works, or how it fits together.

[glenjamin]

For now I reckon the best approach will be to create a little object/function for problem/success, which creates and holds a reference to the overlay module inside it - and then to memoise this into a singleton on window.

This will avoid the double-warn in the console too.

[yyx990803]

Made the reporter a singleton, also made the overlay only attached if there are errors.

[glenjamin]

Could you expand this comment to say why?

Something that mentions multiple bundles will do it

LGTM aside from that

[glenjamin]

Released in 2.10.0

[yyx990803]

👍