Check if the 'mirroring' property exists in media-views.js

[MMDeveloper]

/wp-includes/js/media-views.js

<?php
this.collection.mirroring.args.s 

on line 2121 should be

<?php
                if ( 
    this.collection.hasOwnProperty('mirroring') &&
    this.collection.mirroring.args.s
){

Similar issue
/wp-includes/js/media-views.min.js

[mukesh27]

#53857 was marked as a duplicate.

Trac ticket: https://core.trac.wordpress.org/ticket/53856

[mukesh27]

Hi there!

@MMDeveloper thanks for the ticket.

media-views.js and media-views.min.js is automated build files.

PR added as per your suggestion.

[johnbillion]

@mukesh27 @MMDeveloper How can this bug be reproduced please?

[MMDeveloper]

I think its to do with legacy software. I'm on WordPress 5.8 but the theme has not been updated in many years. So you may not necessarily care. On WordPress Visual editor, I click edit gallery and when I see WordPress Media Gallery, it produces this error in the Google Developer Tools console.

I think it could be a legacy issue, but considering its just checking if a variable exists or not, I didn't think it was a big deal for you guys to implement in next build.

[antpb]

Joe mentioned this was a good candidate to make it back into the 5.9 milestone so we'll be moving it back in. :D Thanks, Joe!

[hellofromTonya]

5.9 Beta 1 is happening in less than 30 minutes. I'm sorry this ticket didn't get a review and testing in time. As it's a bug that was not introduced in 5.9 cycle, moving it to 6.0 to give it the time and attention it deserves.

Also updated the keywords as testing instructions are needed to reproduce the issue and then verify the patch resolves it.

[joedolson]

In 52671:

Comments: Verify 'mirroring' property exists in media views.

Checks that the media collection has a mirroring property before accessing the property in media views.

Props MMDeveloper, mukesh27.
Fixes #53856.

[SergeyBiryukov]

Is there a reason not to just check if ( this.collection.mirroring && ... ) here?

Seems more consistent with seven similar checks in models/attachments.js​, and I think it doesn't matter in this case if the property is directly assigned or inherited, just that it exists.

[joedolson]

Hmm. I didn't question the original patch on that; I doubt there's any particular reason that direct vs inheritance would matter, but I can test, in case.

[joedolson]

this.collection.mirroring instead of hasOwnProperty

[joedolson]

In 52806:

Media: Use consistent mirroring check in media views.

Change the mirroring property verification method to be consistent with other usages across models and attachments, since we don't care whether it's assigned directly on inherited.

Props MMDeveloper, SergeyBiryukov.
Fixes #53856.