Add support for page templates support in CPTs and posts

lib/full-site-editing/page-templates.php

@@ -7,11 +7,13 @@
 
 /**
  * Load the page templates in Gutenberg.
- *
- * @param array $templates Theme page templates.
- * @return array Modified templates.
+ * 
+ * @param array    $templates Page templates.
+ * @param WP_Theme $theme     WP_Theme instance.
+ * @param WP_Post  $post      The post being edited, provided for context, or null.
+ * @return array (Maybe) modified page templates array.
  */
-function gutenberg_load_fse_page_templates( $templates ) {
+function gutenberg_load_fse_page_templates( $templates, $theme, $post ) {
 	if ( ! gutenberg_is_fse_theme() ) {
 		return $templates;
 	}
@@ -25,11 +27,16 @@ function gutenberg_load_fse_page_templates( $templates ) {
 	);
 	$page_templates = array();
 	if ( isset( $data['pageTemplates'] ) ) {
-		foreach ( $data['pageTemplates']  as $key => $page_emplate ) {
-			$page_templates[ $key ] = $page_emplate['title'];
+		foreach ( $data['pageTemplates']  as $key => $page_template ) {
+			if ( ( ! isset( $page_template['postTypes'] ) && 'page' === $post->post_type ) ||
+				( isset( $page_template['postTypes'] ) && in_array( $post->post_type, $page_template['postTypes'], true ) )
+			) {
+				$page_templates[ $key ] = $page_template['title'];
+			}
 		}
 	}
 
 	return $page_templates;
 }
-add_filter( 'theme_page_templates', 'gutenberg_load_fse_page_templates' );
+add_filter( 'theme_post_templates', 'gutenberg_load_fse_page_templates', 10, 3 );
+add_filter( 'theme_page_templates', 'gutenberg_load_fse_page_templates', 10, 3 );