FF103 Errors are serializable (support structuredClone)

[hamishwillee]

FF103 adds support for serializing native error classes in https://bugzilla.mozilla.org/show_bug.cgi?id=1556604#c33

Note that

• this supports both standard and non-standard error properties (name, message, cause, fileName, lineNumber and columnNumber). The stack property is still only supported in nightly.
• it works for all the normal error types except for InternalError
• AggregateError support is in FF but this is not yet in spec so that is added but marked as "non-standard". This includes the errors field.
• I added info about the supported properties as a Note rather than as properties because the spec is fairly loose about what needs to be supported - essentially it is name + message + "any interesting properties.

Related docs work can be tracked in #18208

[hamishwillee]

@queengooborg FYI - would be good to get review on this when you are ready.

[zloirock]

They are serializable from FF103. FF104 can clone Error (but still not DOMException) .stack.

[hamishwillee]

Hi @zloirock - I just noticed I got this wrong - fixed.

[hamishwillee]

PS @zloirock, according to @evilpie FF104 nightly (only) can clone Error.stack. I have captured this in a note since I don't want to do a subfeature for every field that might be serializable. I'll update the note once Error.stack serialization is supported in proper releases.

[evilpie]

PS @zloirock, according to @evilpie FF104 nightly (only) can clone Error.stack. I have captured this in a note since I don't want to do a subfeature for every field that might be serializable. I'll update the note once Error.stack serialization is supported in proper releases.

That's incorrect. We will support stack in 104 not just Nightly. But only in window.postMessage and structuredClone.

[hamishwillee]

Ah, thanks @evilpie . Apologies @zloirock I misinterpreted:

We only support serializing the stack when using the structuredClone API in Nightly at the time of writing this.

So is this right? (just to be very clear):

• FF103 allows Error.stack to be serialized for postMessage()
• FF103 allows Error.stack to be serialized (clonable) for structuredClone but in NIGHTLY only.
• FF104 allows Error.stack to be serialized for both postMessage() and structuredClone() (all builds)
• FF can clone DOMException, but still not DOMException.stack in FF104.

  Does FF have a stack? It isn't in the spec or documented in DOMException (even as a non-standard property). Are we missing any other properties?

So for FF103 we'd have a note like this one: https://github.com/mdn/browser-compat-data/pull/17008/files#r922916460 - for FF104 we will update again.

[zloirock]

IIRC .stack is not serializable / clonable in FF103 and was not even in Nightly, however, I'm not 100% sure about the last statement.

[evilpie]

Correct. There was no stack serialization support at all in FF103 in Nightly or otherwise. 104 supports structuredClone and window.postMessage.

[hamishwillee]

@queengooborg This is now ready for review.