User Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:51.0) Gecko/20100101 Firefox/51.0 Build ID: 20160816030459 Steps to reproduce: 1. Start Nightly 2. Go to about:home 3. Open DevTools > Inspector 4. Open Browser Console (Ctrl+Shift+J) 5. Select any nodes in markup 6. Select any breadcrumbs 7. Select non-node (e.g. <!-- comment ---> or text) 8. Select any breadcrumbs Actual results: In step 8, the following error occurs after selecting non-node. TypeError: this.nodeHierarchy[this.currentIndex] is undefined breadcrumbs.js:499:1 Regression range: https://hg.mozilla.org/integration/mozilla-inbound/pushloghtml?fromchange=a1727a7c7f2f5cb3d732c475567e421aed2f0ba8&tochange=aa4472559aa9a67310e5be2f697252c5db07bd14 Expected results: If selecting non-node, navigation works without error.

Comment on attachment 8781700 [details] Bug 1295564 - fixing aria-activedescendant handling in breadcrumbs when they are unchecked. https://reviewboard.mozilla.org/r/72048/#review70028 ::: devtools/client/inspector/breadcrumbs.js:498 (Diff revision 1) > * @param {DOMEvent} event. > */ > handleFocus: function (event) { > event.stopPropagation(); > > + if (this.currentIndex > -1) { For some reason in one of my profiles with the react devtools addon I still end up with the original error. Works fine in a clean profile, so no problem, but if I switch the condition here to: `if (this.nodeHierarchy[this.currentIndex])` it fixes the problem in both profiles and I don't see a downside, so I'd suggest we change it to that

Comment on attachment 8781700 [details] Bug 1295564 - fixing aria-activedescendant handling in breadcrumbs when they are unchecked. https://reviewboard.mozilla.org/r/72048/#review70030

Pushed by yura.zenevich@gmail.com: https://hg.mozilla.org/integration/mozilla-inbound/rev/5a67b0701200 fixing aria-activedescendant handling in breadcrumbs when they are unchecked. r=bgrins

I have reproduced this bug with Nightly 51.0a1 (2016-08-16) on Windows 8.1 (64 Bit!). This bug's fix is verified on Latest Nightly 51.0a1. Build ID : 20160831030224 User Agent : Mozilla/5.0 (Windows NT 6.3; WOW64; rv:51.0) Gecko/20100101 Firefox/51.0 [bugday-20160831]

Thanks all.