Warnings on dashboard: Notice: Trying to get property of non-object in wp-includes/capabilities.php

[grandslambert]

I just upgraded a local install to 3.1 and have the debug mode on. Now, on the dashboard the "Recent Comments" box is filled with notices. I will attach a screen-shot of the notices. Though this doesn't show when debug mode is off, I have to assume that something isn't working with all of these warnings.

Screenshot of warning notices in the Recent Comments box on the dashboard in 3.1

Another screen shot of the comments page filled with warnings.

Do you have deactivated all your plugins?

Those notices are most likely caused by a plugin doing something wrong.

Put the following gist in your mu-plugins folder to see a backtrace. ​https://gist.github.com/625769

OK, I did a clean install of 3.1 and turned on debug mode and it does not happen. Went back to other install and removed all plugins, still happens. Then I noticed there were some comments for posts that were no longer on the site. Once I deleted those from the database the errors went away. Apparently another bug which I may not be able to track prevented these comments from deleting when the posts were deleted. I will look into that, but perhaps a check to make sure a comment is associated with a post could prevent these errors -though it is not likely to happen all that often.

grandslambert, would be nice if you can add the backtrace (see scribu's comment) to investigate it.

How would that help me if there are no errors showing now? The problem was bad data, likely caused by a bad plugin, and certainly not something that should be the concern of WordPress core developers. I doubt very much that any other user is going to encounter this problem.

Okay, thanks.

Screenshots of notices in the exact place as above, but with ver 3.4

Reopening this ticket, I'm having the same situation.

Twentyeleven, no plugins activated.

Although I had a plugin enabled that created a custom post type, that has comments on their custom post type posts.

More Info: I had attempted to import the "theme unit test" which had issues and failures importing, couldn't retrieve images etc.

notices in the comments section of the wp-admin

Okay, based on the description, this should be reproducible back to 3.0.

So the issue is two-fold:

1. What to do about comments on a post of a non-existent type? and
2. map_meta_cap() needs to be a bit more resilient here.

Is it possible to do a check under the call for get_post_type_object, since it returns null we can gather that it must have existed at some point in time and then refer to using say 'post' as a fallback for the meta_cap ? -- probably could be done cleaner in the function get_post_type_object()

if (is_null($post_type_object)) $post_type_object = get_post_type_object( 'post' );

I don't think we should default to 'post' if the CPT is null.

IMO, the cap check should fail, unless the user has 'moderate_comments'.

Related: ticket:19590:12

Related: #21031