1050104 - It is not possible to override console.log (or set any expandos on console) in a worker because self.console returns a new object each time

Status: RESOLVED FIXED

(Core :: DOM: Workers, defect)

Description

[Jukka Jylänki]

Attachment: worker_consolelog_patch.tar.gz

If one replaces the console.log function in a worker to e.g. post the messages back to main thread instead of printing to console, this assignment is ignored and the worker will keep calling to the original browser-implemented console.log function instead of calling the user-defined function.

See the attached code for a test case. See also https://bugzilla.mozilla.org/show_bug.cgi?id=1049091 where this was first reported.

Comment 1

[Andrea Marchesini [:baku]]

It's possible to replace the entire object: console = { log: function(msg) { .. } }

Comment 2

[Jukka Jylänki]

Thanks, that works. Is there a reason why overriding just a single function is not supported, or was that just accidental?

Comment 3

[Andrea Marchesini [:baku]]

I suspect it's a bug because on main-thread it works.

Comment 4

[Boris Zbarsky [:bzbarsky]]

Andrea, did you read bug 1049091 comment 11?  This is totally a bug, and a memory hog if something uses console in workers.

Comment 5

[(no longer active)]

Attachment: Do not return a new console object every time self.console is called on workers; r=baku

Comment 6

[Boris Zbarsky [:bzbarsky]]

Comment on attachment 8469585 [details] [diff] [review]
Do not return a new console object every time self.console is called on workers; r=baku

Why can't you just make the return type Console* and return mConsole?

Comment 7

[(no longer active)]

I can!

Comment 8

[(no longer active)]

Attachment: Do not return a new console object every time self.console is called on workers; r=baku

Comment 9

[Andrea Marchesini [:baku]]

Comment on attachment 8469628 [details] [diff] [review]
Do not return a new console object every time self.console is called on workers; r=baku

Review of attachment 8469628 [details] [diff] [review]:
-----------------------------------------------------------------

good!

Comment 10

[(no longer active)]

https://hg.mozilla.org/integration/mozilla-inbound/rev/9cc8465f45a5

Comment 11

[(no longer active)]

Backed out because this patch seems to leak the Console object :(

https://hg.mozilla.org/integration/mozilla-inbound/rev/587758056245
https://tbpl.mozilla.org/php/getParsedLog.php?id=45531709&tree=Mozilla-Inbound

Comment 12

[Boris Zbarsky [:bzbarsky]]

Perhaps because WorkerGlobalScope doesn't CC the mConsole member?

Comment 13

[(no longer active)]

Ah, of course, the cycle collector needs to know about mConsole!

https://hg.mozilla.org/integration/mozilla-inbound/rev/cf471a3f661b

Comment 14

[Wes Kocher (:KWierso) (Not reading bugmail; email directly if needed)]

https://hg.mozilla.org/mozilla-central/rev/cf471a3f661b