Publishes a post by transitioning the post status.

function wp_publish_post( $post ) {
	global $wpdb;

	$post = get_post( $post );

	if ( ! $post ) {
		return;
	}

	if ( 'publish' === $post->post_status ) {
		return;
	}

	$post_before = get_post( $post->ID );

	// Ensure at least one term is applied for taxonomies with a default term.
	foreach ( get_object_taxonomies( $post->post_type, 'object' ) as $taxonomy => $tax_object ) {
		// Skip taxonomy if no default term is set.
		if (
			'category' !== $taxonomy &&
			empty( $tax_object->default_term )
		) {
			continue;
		}

		// Do not modify previously set terms.
		if ( ! empty( get_the_terms( $post, $taxonomy ) ) ) {
			continue;
		}

		if ( 'category' === $taxonomy ) {
			$default_term_id = (int) get_option( 'default_category', 0 );
		} else {
			$default_term_id = (int) get_option( 'default_term_' . $taxonomy, 0 );
		}

		if ( ! $default_term_id ) {
			continue;
		}
		wp_set_post_terms( $post->ID, array( $default_term_id ), $taxonomy );
	}

	$wpdb->update( $wpdb->posts, array( 'post_status' => 'publish' ), array( 'ID' => $post->ID ) );

	clean_post_cache( $post->ID );

	$old_status        = $post->post_status;
	$post->post_status = 'publish';
	wp_transition_post_status( 'publish', $old_status, $post );

	/** This action is documented in wp-includes/post.php */
	do_action( "edit_post_{$post->post_type}", $post->ID, $post );

	/** This action is documented in wp-includes/post.php */
	do_action( 'edit_post', $post->ID, $post );

	/** This action is documented in wp-includes/post.php */
	do_action( "save_post_{$post->post_type}", $post->ID, $post, true );

	/** This action is documented in wp-includes/post.php */
	do_action( 'save_post', $post->ID, $post, true );

	/** This action is documented in wp-includes/post.php */
	do_action( 'wp_insert_post', $post->ID, $post, true );

	wp_after_insert_post( $post, true, $post_before );
}