Set Yoast SEO canonical URL meta for given post types and taxonomies to current link and perform given URL replacements.

pronamic-wpseo-set-canonical.php

<?php

/**
 * Set Yoast SEO canonical URL meta for given post types and taxonomies
 * to current link and perform given URL replacements.
 *
 * To run, set query variable: `/wp-admin/?pronamic_set_canonical=true`.
 *
 * @return void
 */
add_action( 'init', 'pronamic_wpseo_set_canonical' );

function pronamic_wpseo_set_canonical() {
	// Post types to process.
	$post_types = array(
		'download',
		'location',
		'market',
		'page',
		'product',
	);

	// Taxonomies to process.
	$taxonomies = array(
		'application',
		'category',
		'download_category',
		'location_category',
		'market_category',
		'product_category',
	);

	// URL replacements.
	$replacements = array(
		'/de-de/' => '/de/',
		'/fr-fr/' => '/fr/',
	);

	/* --- DO NOT EDIT BELOW THIS LINE --- */

	if ( ! filter_has_var( INPUT_GET, 'pronamic_set_canonical' ) ) {
		return;
	}

	// Post types.
    $query = new WP_Query(
		array(
			'post_type'   => $post_types,
			'post_status' => 'any',
			'fields'      => 'ids',
			'nopaging'    => true,
		)
	);

	// Update Yoast SEO canonical URL post meta.
	foreach ( $query->posts as $post_id ) {
		$permalink = get_permalink( $post_id );

		$canonical = strtr( $permalink, $replacements );

		update_post_meta( $post_id, '_yoast_wpseo_canonical', $canonical );
	}

	// Taxonomies.
    $query = new WP_Term_Query(
		array(
			'taxonomy' => $taxonomies,
			'fields'   => 'ids',
		)
	);

	// Update Yoast SEO canonical URL term meta.
	foreach ( $query->terms as $term_id ) {
		$term_link = get_term_link( $term_id );

		$canonical = strtr( $term_link, $replacements );

		update_term_meta( $term_id, '_yoast_wpseo_canonical', $canonical );
	}
}

/**
 * Yoast SEO canonical URL filter for post archives.
 *
 * @return string
 */
add_filter( 'wpseo_canonical', 'pronamic_wpseo_canonical_archive_url' );

function pronamic_wpseo_canonical_archive_url( $canonical ) {
	if ( ! is_post_type_archive() ) {
		return $canonical;
	}

	// Replacements.
	$replacements = array(
		'/de-de/' => '/de/',
		'/fr-fr/' => '/fr/',
	);

	$canonical = strtr( $canonical, $replacements );

	return $canonical;
}