Add mailchimp_sf_list_limit filter to allow modifying the list limit.

includes/admin/templates/settings.php

@@ -51,8 +51,7 @@
 						</p>
 						<form method="post" action="<?php echo esc_url( add_query_arg( array( 'page' => 'mailchimp_sf_options' ), admin_url( 'admin.php' ) ) ); ?>">
 							<?php
-							// we *could* support paging, but few users have that many lists (and shouldn't)
-							$lists = $api->get( 'lists', 100, array( 'fields' => 'lists.id,lists.name' ) );
+							$lists = mailchimp_sf_get_lists();
 							if ( is_wp_error( $lists ) ) {
 								$msg = sprintf(
 									/* translators: %s: error message */

includes/blocks/class-mailchimp-list-subscribe-form-blocks.php

@@ -103,14 +103,7 @@ public function get_lists() {
 			return $lists;
 		}
 
-		// If we don't have any lists, get them from the API.
-		$api = mailchimp_sf_get_api();
-		if ( ! $api ) {
-			return array();
-		}
-
-		// we *could* support paging, but 100 is more than enough for now.
-		$lists = $api->get( 'lists', 100, array( 'fields' => 'lists.id,lists.name,lists.email_type_option' ) );
+		$lists = mailchimp_sf_get_lists();
 		if ( is_wp_error( $lists ) ) {
 			return array();
 		}

includes/class-mailchimp-admin.php

@@ -372,7 +372,7 @@ public function verify_and_save_oauth_token( $access_token, $data_center ) {
 			update_option( 'mc_user', $this->sanitize_data( $user ) );
 
 			// Clear Mailchimp List ID if saved list is not available.
-			$lists = $api->get( 'lists', 100, array( 'fields' => 'lists.id,lists.name,lists.email_type_option' ) );
+			$lists = mailchimp_sf_get_lists();
 			if ( ! is_wp_error( $lists ) ) {
 				$lists         = $lists['lists'] ?? array();
 				$saved_list_id = get_option( 'mc_list_id' );

mailchimp.php

@@ -546,13 +546,8 @@ function mailchimp_sf_change_list_if_necessary() {
 		return;
 	}
 
-	$api = mailchimp_sf_get_api();
-	if ( ! $api ) { return; }
-
-	// we *could* support paging, but few users have that many lists (and shouldn't)
-	$lists = $api->get( 'lists', 100, array( 'fields' => 'lists.id,lists.name,lists.email_type_option' ) );
-
-	if ( ! isset( $lists['lists'] ) || is_wp_error( $lists['lists'] ) ) {
+	$lists = mailchimp_sf_get_lists();
+	if ( is_wp_error( $lists ) || ! isset( $lists['lists'] ) ) {
 		return;
 	}
 
@@ -998,3 +993,27 @@ function mailchimp_sf_get_access_token() {
 function mailchimp_sf_should_display_form() {
 	return mailchimp_sf_get_api() && ! get_option( 'mailchimp_sf_auth_error' ) && get_option( 'mc_list_id' );
 }
+
+/**
+ * Get Mailchimp Lists.
+ *
+ * @since x.x.x
+ * @return array|WP_Error|false List of Mailchimp lists, or an error/false from the API request.
+ */
+function mailchimp_sf_get_lists() {
+	/**
+	 * Filter the limit of lists to fetch.
+	 *
+	 * This value is sanitized to a positive integer and clamped before the API request.
+	 * Defaults to 100. 1000 is the maximum allowed by the API. 1 is the minimum allowed.
+	 */
+	$limit = apply_filters( 'mailchimp_sf_list_limit', 100 ); // Default to 100.
+	$limit = max( 1, min( 1000, absint( $limit ) ) );
+
+	$api = mailchimp_sf_get_api();
+	if ( ! $api ) {
+		return array();
+	}
+
+	return $api->get( 'lists', $limit, array( 'fields' => 'lists.id,lists.name,lists.email_type_option' ) );
+}