1215502 - TypeError: 'toString' called on an object that does not implement interface Exception

Status: VERIFIED FIXED

Description

[Henrik Skupin (:whimboo)]

I can see this exception when I was investigating a test failure in our Firefox ui tests logged as bug 1215499.

The following output is visible in the Gecko log:

MARIONETTE LOG: INFO: TEST-START: c:\jenkins\workspace\release-mozilla-release_functional\venv\Lib\site-packages\firefox_ui_tests\functional\private_browsing\test_about_private_browsing.py:testCheckAboutPrivateBrowsing
1444997539656 Marionette: Element does not have an accessible object*************************
A coding exception was thrown in a Promise rejection callback.
See https://developer.mozilla.org/Mozilla/JavaScript_code_modules/Promise.jsm/Promise

Full message: TypeError: 'toString' called on an object that does not implement interface Exception.
Full stack: error.isError@chrome://marionette/content/error.js:104:12
error.isWebDriverError@chrome://marionette/content/error.js:112:10
error.toJSON@chrome://marionette/content/error.js:72:8
Response.prototype.sendError@chrome://marionette/content/command.js:100:16
Handler.prototype.process@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:925:21
this.PromiseWalker.walkerLoop@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:801:7
this.PromiseWalker.scheduleWalkerLoop/<@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:740:39

*************************
Marionette threw an error: TypeError: 'toString' called on an object that does not implement interface Exception.
error.isError@chrome://marionette/content/error.js:104:12
error.isWebDriverError@chrome://marionette/content/error.js:112:10
error.toJSON@chrome://marionette/content/error.js:72:8
Response.prototype.sendError@chrome://marionette/content/command.js:100:16
Handler.prototype.process@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:925:21
this.PromiseWalker.walkerLoop@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:801:7
this.PromiseWalker.scheduleWalkerLoop/<@resource://gre/modules/Promise.jsm -> resource://gre/modules/Promise-backend.js:740:39

Comment 1

[Andreas Tolfsen ﹝:ato﹞]

The error.toJSON function has since been removed.  Does this still reproduce?

Comment 2

[Henrik Skupin (:whimboo)]

Yes, still a problem with a Nightly build from Tuesday:

Full message: TypeError: 'toString' called on an object that does not implement interface Exception.
Full stack: error.isError@chrome://marionette/content/error.js:78:12
error.isWebDriverError@chrome://marionette/content/error.js:86:10
Response.prototype.sendError@chrome://marionette/content/command.js:89:12

Comment 3

[Andreas Tolfsen ﹝:ato﹞]

This is caused by an incomplete test for whether val in error.isError is an XPCOM exception.  The correct check would be to do

    val instanceof Ci.nsIException

Comment 4

[Andreas Tolfsen ﹝:ato﹞]

Created attachment 8705146 [details]
MozReview Request: Bug 1215502: Perform nsIException instance test for XPCOM exceptions

The current test of the `result' property does not always pass for all
types of XPCOM exceptions.  A safer test is to do an instance check
against Components.interfaces.nsIException.

This fixes hangs such as the one described in bug 1202576.

r=dburns

Review commit: https://reviewboard.mozilla.org/r/29881/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/29881/

Comment 5

[Andreas Tolfsen ﹝:ato﹞]

Created attachment 8705147 [details]
MozReview Request: Bug 1215502: Send wrapped WebDriverError to client

This fixes serialisation of XPCOM exceptions to the client.
Response.sendError was incorrectly serialising the err input variable
instead of the wrapped WebDriverError, we.

r=dburns

Review commit: https://reviewboard.mozilla.org/r/29883/diff/#index_header
See other reviews: https://reviewboard.mozilla.org/r/29883/

Comment 6

[David Burns :automatedtester]

Comment on attachment 8705146 [details]
MozReview Request: Bug 1215502: Perform nsIException instance test for XPCOM exceptions

https://reviewboard.mozilla.org/r/29881/#review26687

Comment 7

[David Burns :automatedtester]

Comment on attachment 8705147 [details]
MozReview Request: Bug 1215502: Send wrapped WebDriverError to client

https://reviewboard.mozilla.org/r/29883/#review26691

Comment 8

[Pulsebot]

https://hg.mozilla.org/integration/mozilla-inbound/rev/26a9634f6ec2
https://hg.mozilla.org/integration/mozilla-inbound/rev/a9da976060a8

Comment 9

[Henrik Skupin (:whimboo)]

Thanks for the quick fix Andreas! I wonder if a unit test would also be good to have here.

Comment 10

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/mozilla-central/rev/26a9634f6ec2
https://hg.mozilla.org/mozilla-central/rev/a9da976060a8

Comment 11

[Henrik Skupin (:whimboo)]

This looks great! The hang (bug 1202576) is fixed which was caused by this bug.

David, can we please get this backported to the aurora branch to have it included in the next ESR? Thanks.

Comment 12

[Carsten Book [:Tomcat]]

https://hg.mozilla.org/releases/mozilla-aurora/rev/dcd136c18c7a
https://hg.mozilla.org/releases/mozilla-aurora/rev/9e810b77b412