Flaky subtest of web-platform-tests/html/dom/interfaces.html (XMLDocument#all)

Confirmed Issue #12047069 • Assigned to Thomas M.


Philip J.
May 17, 2017
This issue is public.
Found in
  • Microsoft Edge
Reported by 1 person

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Steps to reproduce

This came up in https://github.com/w3c/web-platform-tests/pull/5942 on Edge 14, but has also been confirmed in Edge 15.

At wpt commit 7005b60351c6bd8dc6be07e2a290f5df3909f134, http://w3c-test.org/html/dom/interfaces.html does not produce reliable results.

The subtest that sometimes fails and sometimes passes is 'Document interface: document.implementation.createDocument(null, "", null) must inherit property “all” with the proper type (75)'

The test itself is probably invalid, but when it fails it’s here:

It seems like the "property = obj[member.name]" bit in “IdlInterface.prototype.test_interface_of” doesn’t always result in the same value.

An attempt to minify the test in https://github.com/w3c/web-platform-tests/pull/5963 made the problem go away.

In https://github.com/w3c/web-platform-tests/pull/5942#issuecomment-301896566 gsnedders has guesses about the cause.


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    Comments and activity

    • I’ve been unable to reproduce this in Edge 15 at all; in Edge 14 it’s completely stable with the devtools open which suggests my hypothesis about it being a JIT issue is accurate.

      I’m fairly certain property = obj[member.name] is consistent; it’s when it then calls a function, binding that property to value as an argument and then doing typeof value it’s inconsistent, sometimes returning “undefined” and sometimes "object". Given the magic around HTMLAllCollection, this isn’t the most surprising of bugs. :)

    • OK, no, finally got it to repro. After many, many, many reloads. Can’t really tell if having devtools open makes any difference because it’s so rare.

    • Microsoft Edge Team

      Changed Assigned To to “Brian T.”

      Changed Assigned To from “Brian T.” to “Paul L.”

      Changed Status to “Confirmed”

      Changed Assigned To from “Paul L.” to “Sandeep A.”

      Changed Assigned To from “Sandeep A.” to “Louis L.”

      Changed Assigned To from “Louis L.” to “Thomas M.”

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