1102407 - [e10s] Web Of Trust (WOT) fails to watch dynamic changes, with " TypeError: Argument 1 of MutationObserver.observe does not implement interface Node"

Status: RESOLVED INCOMPLETE

(WebExtensions :: General, defect)

Description

[Daniel Holbert [:dholbert]]

STR:
0. Be using e10s (currently on by default in Nightly)

1. Install Web of Trust extension from
  https://addons.mozilla.org/en-US/firefox/addon/wot-safe-browsing-tool/

2. Log into Facebook.

3. Inspect your terminal. (I'm assuming you started Firefox from the terminal & can see its terminal output)

ACTUAL RESULTS: This appears in your terminal.
wot_search.watch: failed with TypeError: Argument 1 of MutationObserver.observe does not implement interface Node.


Basically, WOT registers a mutation observer so it can scan the URLs of new links that appear dynamically on your timeline (and label them as safe/unsafe).  But it seems to be failing to hook up the mutation observer, in e10s mode.

Comment 1

[Daniel Holbert [:dholbert]]

Also, FWIW: WOT is a "Featured" add-on on AMO, with nearly 1.3 million users. It's our 9th-most-popular extension, according to https://addons.mozilla.org/en-US/firefox/extensions/?sort=users

The current WOT version on AMO is 20131118 (released on 2013-11-18, just over a year ago). So, not too surprising that it doesn't quite work with e10s.

We should probably reach out to them to let them know about this bug, with recommended workarounds for setting up a mutationobserver in e10s builds.  [--> CC'ing the two bugzilla users who have "mywot.com" email addresses.]

Comment 2

[Daniel Holbert [:dholbert]]

Attachment: search.js from the WOT extension's JAR file (which has the failing "observe" call)

Comment 3

[Daniel Holbert [:dholbert]]

FWIW, if I add logging to print out the thing we're passing to 'observe', I get this in non-e10s mode:
> Calling observe with content: [object HTMLDocument]

but I get this in non-e10s mode:
> Calling observe with content: [object CPOW [object HTMLDocument]]

Comment 4

[Chris Peterson [:cpeterson]]

The WOT add-on was reported as working in bug 1002880, so this might be a recent regression.

Comment 5

[Daniel Holbert [:dholbert]]

(In reply to Chris Peterson (:cpeterson) from comment #4)
> The WOT add-on was reported as working in bug 1002880, so this might be a
> recent regression.

I don't think so -- note that the only thing broken here is the mutation observer (and you can only tell by watching your terminal, or perhaps by noticing un-WOT-annotated links show up on Facebook).

I'll bet we just didn't notice that the mutation observer stuff was broken over in bug 1002880.

Comment 6

[Daniel Holbert [:dholbert]]

Note that this error-message doesn't seem to show up in my browser console -- only in my terminal (via stdout). So, it would've been easy to miss.

Also: as you might expect, I can confirm that WOT is failing to annotate links in dynamically-loaded chunks of Facebook, when e10s is enabled (presumably due to the observe() call in this bug). So for example, I see green/orange/red WOT icons next to links that are shown in my initial Facebook load, but if I scroll to the bottom to pull in more content, then *that* content doesn't have WOT icons next to its links.

Comment 7

[:shell escalante]

retest

Comment 8

[Firefox Bug Husbandry Bot]

With Firefox 57 only WebExtensions are permitted and are, by default, e10s compatible.