1486259 - "No element selected" in Developer Tools Inspector, even when items are selected

Status: NEW

(DevTools :: Inspector, defect, P2)

Description

[repertor]

I now have to regularly close and reopen the Developer Tools, as while the Inspector can select elements on the page and highlight the appropriate node, the corresponding styles never display. Instead, the styles panel only displays "No element selected." even when selecting a different node in the adjacent panel. The Layout, Computed, etc panels also do not update. Closing the Developer Tools window and reopening fixes the issue, but only temporarily.

I am using macOS 10.13.6, and both Firefox Nightly and the Developer Tools are fullscreen on separate displays.

Comment 1

[repertor]

It just happened again when I refreshed a page I was inspecting. Neither window was fullscreen, but I did have the Developer Tools in a separate window still.

Comment 2

[Julian Descottes [:jdescottes]]

Can you share a URL and a step by step scenario so that we can reproduce this issue? Thanks.

Comment 3

[repertor]

It happens on localhost while I'm doing internal design, as well as many other domains.

Since it happens unexpectedly, I'm not able to find the exact workflow that triggers it. All I know is that I'll have the Developer Tools window open for a tab, and as I'm using it through refreshes and switching between applications at some point styles will no longer display. I can select other nodes in the document or refresh the tab, but nothing restores functionality besides closing the window and reopening Developer Tools for that tab. I have to do this repeatedly because it always happens eventually.

Comment 4

[Martin Balfanz [:mbalfanz]]

STR:
1. Visit a page and open devtools with a panel other than the inspector (e.g. console)
2. Activate RDM
3. Right click an element and select "Inspect element"

Comment 5

[c.hubscher]

Having the same issue as well, a little pesky.

Comment 6

[Gabriel Luong [:gl] (ΦωΦ)]

Not able to reproduce this recently, perhaps fixed in another bug? Unassigning for now.

Comment 7

[repertor]

It's not as bad as it was, but I'm still able to trigger it. Just was testing some JS/CSS on localhost, and after a couple page refreshes the problem happened again where "No element selected." displays when elements are selected either through the DOM list to the left or with the element picker.

Comment 8

[Tom]

I can verify this bug still exists.

MacBook Pro 10.13.6
Firefox 62.0.2 (64-bit)

Select div using Inspector
No element selected is displayed

Comment 9

[aequalsb]

I can also verify this problem still exists -- 

firefox 62.0.3
macbook 10.11.6

same description as above: "Select [any element] using Inspector
No element selected is displayed"

If I reopen the URL in a new tab, or sometimes a new window, or sometimes a new private window, I can get it to start working again -- sometimes it takes 3-4 tries before it kicks in again. Refreshing has not ever fixed it. No pattern that i can recognize causes it... it doesn't happen after anything in particular that I've noticed anyway...

Comment 10

[aequalsb]

also... this is not a rare occurrence... it happens regularly

Comment 11

[Patrick Brosset <:pbro>]

Sorry about the delay on this bug, but it's unfortunately a difficult problem that doesn't always occur for everybody, and therefore is hard to investigate.
I'm trying to reproduce the issue now, but can't. Comment 0, comment 8 and comment 9 mention using a macbook, so that's what I'm doing too. I'm testing this with Firefox 64 and 65.

Apart from Martin in comment 4 (and bug 1487284 which Julian linked), there's no mention of RDM. So I'm not quite sure what other scenario to test.
I've tested exactly like Martin said, and I've refreshed the page many times. I've not seen the problem myself so far.

@aequalsb: by any chance, do you have RDM (Responsive Design Mode) open when it happens?
@repertor: same question to you?

Also, to both of you, whenever it happens, are there errors in the browser console (cmd+shift+J)? If so could you please paste them here?

Comment 12

[aequalsb]

firefox 62.0.4
macbook with mac os 10.11.6 el capitan

i tried to trigger the problem but could not -- i opened multiple tabs simultaneously, multiple windows simultaneously, multiple websites simultaneously, switched back and forth between Responsive Mode, monitored the console during multiple reloads, simultaneous loads/reloads, loading the same website in multiple tabs, etc, etc

most of the time the issue rears it's head is when i'm hammering away at a site making multiple stylesheet edits and reloading frequently. then, suddenly, i can no longer see rules in the inspector and my work is halted as i try to "unhook" the inspector from whatever it's hung on

the most common method that seems to give me the most influence over clearing the issue is to open a new private window to the URL in question -- sadly that is NOT 100% of the time

i wonder at times if it's heavy RAM usage from javascripts running in multiple tabs or some other runaway resource usage --
but quitting and restarting the browser does NOT seem to affect the issue at all

i love firefox and i love the firefox inspector -- both over all other browsers so i continue to encounter the problem on a regular basis

i will still use firefox primarily and endure the issue, but, man, would i love to see it fixed -- i've donated and will again!

thanks!

Comment 13

[aequalsb]

(In reply to aequalsb from comment #12)

i'm running on an old machine from 2009 -- perhaps that's a factor?

MacBook Pro (15-inch, Mid 2009)
CPU : 2.66 GHz Intel Core 2 Duo
RAM : 4 GB 1067 MHz DDR3

Comment 14

[aequalsb]

i have just recently experienced this again and wanted to share to help recreate the problem... i just had "the problem" on my first attempt to "inspect element" after waking my computer from sleep

wondering if computer sleep/wake up is our missing factor

Comment 15

[aequalsb]

restarting the browser did NOT fix the problem

logging out/in did NOT fix the problem

using "inspect element" on another site, in another tab, same window : no problem, it worked fine

returning to the problem tab : problem still exists

super refreshing did NOT fix the problem

using "select element" by clicking icon and then an element did NOT fix the problem

using "inspect element" from context menu did NOT fix the problem

i also just validated all my stylesheets for the site and got perfect validation for all (total of 6) but it did NOT fix the problem

after closing the offending tab, then opening a new tab to the same URL : problem GONE! (but this is not reliable because i've tried that on other occasions -- when the problem finally disappears, it's too difficult to pinpoint what helped because it's apparently random)

are we dealing with a caching issue here?

hope all this helps...

Comment 16

[Elisa]

Following as having the same issue. I don't use any Cache so I doubt it's a cache issue. Could it have some connection to style Versioning or compressed css?

Comment 17

[aequalsb]

hmm... i do have a built-in feature in my WordPress themes to append a timestamp to css/img/etc requests when i flag it with a GET variable as a cache-buster

Comment 18

[Elisa]

Same here, Joomla uses Script and Style Versioning... maybe this leads to a solution. It's such an annoying bug and I am not very happy with switching my default Browser again :(

Comment 19

[Patrick Brosset <:pbro>]

No response from valcus. Clearing the needinfo.
No progress on this bug since I have not been able to replicate it.
Does this still happen for people? If someone was able to provide a set of steps that will reproduce the problem, that'd be great.

Comment 20

[Elisa]

Yes it's still happening regulary and no possibilty to replicate why it's happening. Often it's happening while working on the CSS of a website. Inspecting Element » Changing SCSS and recompile » Reloading Website » Inspector does not show anything anymore. But it's not happening always - so hard to say what it is...

Comment 21

[aequalsb]

the way Elisa describes it... that's what i was experiencing on a regular basis... however, i have been working on a number of sites... i have done a lot of updating to the latest versions of WordPress and to my own custom parent theme for WordPress... including extensive architectural and CSS revisions... and after all the updating, i have not experienced this "bug" in quite a long time now... previously, i had always wondered if it related to my CSS... but i investigated that and found all my stylesheets validated with W3C service... perhaps it is related to my previous HTMl and CSS combinations... but this i know... it hasn't happened in a LONG time...

Comment 22

[Elisa]

Unfortunately it’s still happening :-( very annoying.
No chance to fix it?