Use publish_post meta cap in core instead of publish_posts

[manfcarlo]

The basic idea of the Contributor role is that people can create and edit drafts, but not publish them. When a user is a Contributor, in place of the Publish button, there is the alternate facility to save the post as Pending and wait until an Editor or Administrator publishes it.

Obviously, the idea of this is to require any posts to be manually reviewed before they can be published.

However, in some cases, site owners may want to automate this review process. In other words, let Contributors publish their own posts if those posts meet certain criteria.

For example, if the only check that the site owner deems necessary is that the post is no more than 1,000 words, there should be no need to manually review every post. The system should be configurable such that the publish facility is available to Contributors as long as the post is 1,000 words or less, but is not available if the post exceeds 1,000 words.

#21288 created a publish_post meta capability. Although it simply maps to publish_posts by default, plugins could potentially filter map_meta_cap and bypass publish_posts if certain criteria are met (such as, for example, the post word count.)

The problem is that core barely ever checks the publish_post meta capability. I could only find literally one case of it in all of core. In all other cases, core directly accesses the publish_posts property on the post type object, making it impossible for plugins to create an automated review process.

This could be very easily fixed by simply changing these checks from the general post type capability to the meta capability.

[johnbillion]

Thanks for the report @manfcarlo! This was already reported in #42464. It would be great to fix this but there hasn't been much traction so far. If you'd like to work on a patch, that would be great!

[johnbillion]

Whoops, I referenced the wrong ticket there. Should have been #40197.