Post content blank after disabling Yoast SEO

Question

I'm trying to disable the Yoast SEO plugin from a very simple site with a custom theme. After disabling the plugin, posts do not have any content -- titles work, just the_content is empty. Pages are fine. If I re-enable the plugin, the post content comes back. The problem does not appear if I switch to one of the default Twenty* themes.

It seems like something is messing up the $post data early on, logging from the the_content filter at all priorities yields an empty string. Error logs are empty. My guess is something calls a Yoast function or filter somewhere, but I haven't found anything yet.

WordPress is a clean v4.7.5, Yoast SEO is v4.8 (both latest versions, fresh installs). The only other active plugin is Advanced Custom Fields Pro. I'm able to recreate this on multiple servers.

Answer 1

Turns out the single-post.php template was missing a call to the_post(). Since that function initializes all the postdata used by functions like the_content(), WordPress had nothing to display.

As for Yoast SEO, I'm guessing it calls the_post() somewhere early on which would populate the WordPress global variables. If the theme was written with Yoast SEO enabled, no one would ever have noticed the omission.