multiple custom post types in pre_get_post filter break body_class

[norcross]

Issue: when viewing a custom post type archive template, and having added a pre_get_posts filter to display two separate custom post types on that page, the body_class function breaks trying to process an array to string conversion

[norcross]

checking for post_type query_var as an array or single

[SergeyBiryukov]

25341.diff​ is a simplified version.

[SergeyBiryukov]

In 25471:

Expect a possible array of post types in get_body_class(). props norcross. fixes #25341.

[nacin]

is_post_type_archive() is not supposed to return true when there are multiple post types being queried. At least, that was my assumption.

Can we investigate how this can happen?

[norcross]

the Codex indicates that it'll return a string or array, and says multiple could exist: ​http://codex.wordpress.org/Function_Reference/is_post_type_archive

based on the docs, it's because you can declare one CPT or check for a whether you are on any CPT archive page.

[nacin]

is_post_type_archive is only set to true when if ( !empty( $qv['post_type'] ) && ! is_array( $qv['post_type'] ) ) {. norcross, you reported this against "trunk" originally. Could anyone actually reproduce this in 3.6? Cause it looks like [25312] broke this. See also #18614 where I suggested a revert.

[norcross]

My mistake re: trunk, it should have been 3.6.1

[norcross]

Replying to nacin:

is_post_type_archive is only set to true when if ( !empty( $qv['post_type'] ) && ! is_array( $qv['post_type'] ) ) {. norcross, you reported this against "trunk" originally. Could anyone actually reproduce this in 3.6? Cause it looks like [25312] broke this. See also #18614 where I suggested a revert.

My mistake re: trunk, it should have been 3.6.1

[SergeyBiryukov]

Replying to nacin:

is_post_type_archive is only set to true when if ( !empty( $qv['post_type'] ) && ! is_array( $qv['post_type'] ) ) {.

Right, but the code attached to pre_get_posts (which makes post_type an array) runs after that, not before.

Replying to nacin:

Could anyone actually reproduce this in 3.6?

I was able to reproduce the post-type-archive-Array class in both 3.6 and 3.6.1.

Also got a notice from get_post_type_object()​, which appears to be fixed in [25312]:

Warning: Illegal offset type in isset or empty in wp-includes/post.php on line 1038

[nacin]

Okay, the direction of this fix is proper. But, we should only add one post type as a body class — the rest of post type archives is limited to the first post type listed, as it is specifically designed to not be for multiple post types. That also has the result of not being a major behavior change, while optionally allowing for multiple body classes later.

[nacin]

In 25745:

Only add one body class when multiple post types manage to be present for a post type archive due to pre_get_posts manipulation.

fixes #25341.