1876221 - Assert.sys.mjs tries to JSON.stringify XPCOM objects, fails, and this takes a long time

Status: RESOLVED FIXED

(Testing :: General, defect)

Description

[Geoff Lankow (:darktrojan)]

I've been investigating bug 1860239, which is about a mochitest taking an extraordinary amount of time when run on the Windows CI. (Up to 15 minutes, when on my machine I can run it in 20 seconds.)

I've found the cause is (at least partly) the logging of some Assert calls with complex XPCOM objects. In trying to work out what to log, the code calls JSON.stringify on the objects and when that fails reverts to calling toString. I don't know why, but stringify is taking a very long time to work out that it cannot succeed.

I propose to just avoid calling stringify for any object that has a QueryInterface function. This speeds up the test in question a lot.

Comment 1

[Geoff Lankow (:darktrojan)]

Attachment: Bug 1876221 - Avoid calling JSON.stringify on XPCOM objects in Assert.sys.mjs. r=jmaher

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/78e9fd141aaf
Avoid calling JSON.stringify on XPCOM objects in Assert.sys.mjs. r=jmaher

Comment 3

[Norisz Fay [:noriszfay]]

https://hg.mozilla.org/mozilla-central/rev/78e9fd141aaf