Serialization?

[jasnell]

When the standard definition of APIs indicate that an interface is Serializable, is that a requirement for the minimum common API? For instance, MessagePort is Serializable, but in workers we do not implement that part yet.

[andreubotella]

MessagePort is Transferable, rather. But the same applies to Serializable interfaces.

I would say yes: we do include structuredClone() in the minimum common API, and you would expect at least all of the minimum common APIs to work with structuredClone() as they are spec'd to do so.

Now, the problem is, this might be tricky. For MessagePort in particular, the goal of transferring it is to make it available to a different agent (e.g. a worker, or in the web a cross-origin window). But in the minimum common API we don't define workers, or any other way of having multiple agents. And while naively I would assume transferring MessagePort over structuredClone() would not be that hard to implement¹, it's definitely harder to implement transferring it cross-agent – and if it works with structuredClone(), I would be surprised if it failed on worker.postMessage().

Footnotes

1. Note that I say this after having had to look in depth at Firefox's implementation of MessagePort recently, including the transferring behavior. ↩