What should [bw_link ID] do when ?p=ID would produce a 404? about oik

[bobbingwide]

The current logic uses get_permalink( $id ) to determine the permalink.

• When passed a post ID, get_permalink calls get_post() to access the post.
• It then checks the post_type to determine how to create the permalink - returning the correct format for "page", "attachment" and any registered post type that's not _builtin

Everything else is treated as a "post" using the permalink_structure option.

get_permalink() invokes the 'pre_post_link' filter first ( incorrectly documented as 'Only applies to posts with post_type of 'post' ). This filter hook is not normally implemented, so the permalink structure to be used is unchanged.

And just at the end of the function it invokes the "post_link" filter, also not normally implemented.

Conclusion

We could consider implementing the "post_link" filter to null out the result when the post type is not registered. But I don't think it's necessary.

I might raise a WordPress TRAC on the docblock for 'pre_post_link' though.