624506 - postMessage() should not accept non-string messages if it doesn't support them

Status: RESOLVED DUPLICATE of bug 553125

(Core :: DOM: Core & HTML, defect)

Description

[david]

The postMessage() implementation in Firefox 4b8 accepts any value as the first argument to postMessage(), but apparently just converts it to a string and sends the string as the message instead of using the structured clone algorithm as required by HTML5.

If you're not going to implement this completely in FF4, I think it would be better for compatibility if FF threw an error if the argument was anything other than a string.  Otherwise you run the risk of sites coming to rely on the toString() behavior and failing when the spec is properly implemented.

(This bug is probably mis-categorized: I put it in "DOM: Mozilla Extensions" only because that is where the only other postMessage() bug report I could find is.)

Comment 1

[Boris Zbarsky [:bzbarsky]]

postMesage on a worker does the structured clone thing.  It's only postMessage on Window objects that ends up doing toString.

Ben, is there a reason we don't do structured cloning for postMessage on windows?  Or does that just predate the structured clone spec changes?

Comment 2

[Ben Turner (not reading bugmail, use the needinfo flag!)]

It just predates. There's probably another bug open.

Comment 3

[Boris Zbarsky [:bzbarsky]]

Ah, indeed.

Comment 4

[david]

Sorry for the dup.  I'm very surprised that searching Bugzilla for the string "postMessage" does not match "window.postMessage"!

Comment 5

[Boris Zbarsky [:bzbarsky]]

It did for me once I did the search...  Might depend on the exact search box you're using, though.