1056182 - Add window.internals debug functions (garbage collection, etc.), protected by a pref

Status: NEW

(Core :: DOM: Core & HTML, defect, P5)

Description

[Christian Holler (:decoder)]

Chrome has a window.internals object that is available only with a specific command line flag/pref and exposes all sorts of testing functions like GC. Some of our guests at the fuzzing work week mentioned yesterday, that our way of providing these test functions (through Jesse's addon), makes automation more complex and caused them a few problems when they started writing fuzzers for Firefox.

I think making this a native feature of the browser (of course protected by a pref) is beneficial as it makes the browser testing easier and a little more uniform. It also makes reproducing easier for our developers, once a test depends on such an internal function.

I'd be willing to implement this (given I find out how).

Comment 1

[Gary Kwong [:gkw] [:nth10sd] (NOT official MoCo now)]

I recall marionette had a pref *and* a run-time CLI flag to prevent this from being accidentally turned on in release builds, and the same solution could be in use here.

Comment 2

[:Ms2ger (he/him; ⌚ UTC+1/+2)]

Shouldn't be too hard to add a [Pref=...] readonly attribute Internals internals; to Window.webidl.

Comment 3

[Boris Zbarsky [:bzbarsky]]

I'm happy to guide implementation.  This should be pretty easy now that Window is on Web IDL bindings.

Basically you define an IDL interface like this:

  [NoInterfaceObject]
  interface TestingFunctions {
    // Your functions here
  };

and add this to Window.webidl:

  [Pref="whatever.something"] // Or a Func if you want enabling to be more complicated
  readonly attribute TestingFunctions internals;

and then of course implement the TestingFunctions interface.  Whether to do that in JS or C++ depends on what we want to expose on there.

Comment 4

[Jesse Ruderman]

Exposing Components.utils.getJSTestingFunctions() this way sounds great. And maybe a few of the other things https://www.squarefree.com/extensions/domFuzzLite3.xpi offers, such as cycle collection and enabling accessibility.

I'd prefer for it to only expose "fuzzing-safe" functions.

Comment 5

[Firefox Bug Husbandry Bot]

https://bugzilla.mozilla.org/show_bug.cgi?id=1472046

Move all DOM bugs that haven’t been updated in more than 3 years and has no one currently assigned to P5.

If you have questions, please contact :mdaly.