Can't add new post for registered custom post type

@jmires, do you have any more details about the conflict involved? I’ve found the same issue with a plugin I’m not able to do without.

Thanks, nice idea but no luck 🙁 I might have a quick look at the code anyway, got nothing else to go on…

Solved it. Turns out the fault wasn’t in the plugin, it was some code in my custom theme which only ran when that plugin’s active (because a bit of the code depends on that plugin).

Anyway, here’s the code. It’s part of a hack I did to allow articles to be credited to multiple authors, so I replaced the standard author meta box with a custom field, and this passes the first of the multiple authors through to the standard author field. It’s intended for when the post is saved, but auto-drafts where obviously causing a problem.

add_filter( 'wp_insert_post_data', 'aotc_post_data_filter', 10, 2 );
function aotc_post_data_filter( $data, $postarr ) {

	// Post author for articles
	if ( $data['post_type'] == 'article' && PILAU_PLUGIN_EXISTS_DEVELOPERS_CUSTOM_FIELDS ) {
		// First of the multiple authors
		$data['post_author'] = $postarr[ slt_cf_field_key( 'article_author' ) ][0];
	}

	return $data;
}

The solution was to add, in the if condition, a test for the existence of $postarr[ slt_cf_field_key( 'article_author' ) ]. I guess when an auto-draft was being saved for a new article, there’s no custom fields in the $postarr, and post_author gets set to null or something, screwing up capabilities checks.

This code was working fine until very recently – either 4.4. or 4.4.1. I imagine it’s the case that WP core has tightened up some sloppy coding that allowed my sloppy coding to work.

Anyway, this was triggering the ‘Submit for review’ instead of ‘Publish’ button, based on the same zero post ID issue as above. Hopefully this solution adds to the pile of remedies for this symptom!