Fix Polylang incompatibility with multisite fields

Author: HPiirainen

CHANGELOG.md

@@ -4,6 +4,9 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
 and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.html).
 
+### Fixed
+- Fix Polylang incompatibility with multisite fields.
+
 ## [1.37.0] - 2021-11-30
 
 ### Changed

src/Fields/MultisitePostObject.php

@@ -116,7 +116,22 @@ public function get_post_title( $post, $field, $post_id = 0, $is_search = 0 ) {
              */
             public function render_field( $field ) {
                 \switch_to_blog( $field['blog_id'] );
-                parent::render_field( $field );
+
+                // If Polylang is active, we need to switch the global curlang manually
+                // as switch_to_blog does not do that in admin views.
+                // If this is not done, the field may not find its saved value if the taxonomy term IDs
+                // do not match between all sites.
+                if ( function_exists( 'pll_default_language' ) ) {
+                    $restore_curlang = \PLL()->curlang;
+                    $lang = \PLL()->model->get_language( $restore_curlang->slug );
+                    \PLL()->curlang = $lang ?: \PLL()->model->get_language( \pll_default_language() );
+                    parent::render_field( $field );
+                    \PLL()->curlang = $restore_curlang;
+                }
+                else {
+                    parent::render_field( $field );
+                }
+
                 \restore_current_blog();
             }
 

src/Fields/MultisiteRelationship.php

@@ -124,7 +124,20 @@ public function get_post_title( $post, $field, $post_id = 0, $is_search = 0 ) {
         public function render_field( $field ) {
             \switch_to_blog( $field['blog_id'] );
 
-            parent::render_field( $field );
+            // If Polylang is active, we need to switch the global curlang manually
+            // as switch_to_blog does not do that in admin views.
+            // If this is not done, the field may not find its saved value if the taxonomy term IDs
+            // do not match between both sites.
+            if ( function_exists( 'pll_default_language' ) ) {
+                $restore_curlang = \PLL()->curlang;
+                $lang = \PLL()->model->get_language( $restore_curlang->slug );
+                \PLL()->curlang = $lang ?: \PLL()->model->get_language( \pll_default_language() );
+                parent::render_field( $field );
+                \PLL()->curlang = $restore_curlang;
+            }
+            else {
+                parent::render_field( $field );
+            }
 
             \restore_current_blog();
         }