From ed395350fab470028e30c06f8cda463c242cad58 Mon Sep 17 00:00:00 2001
From: okmttdhr <okmttdhr@users.noreply.github.com>
Date: Mon, 11 Sep 2023 15:36:06 +0900
Subject: [PATCH] Add a notice if a theme is requested too early when
 previewing a theme

---
 src/wp-includes/theme-previews.php | 30 ++++++++++++++++++++++++++++++
 1 file changed, 30 insertions(+)

diff --git a/src/wp-includes/theme-previews.php b/src/wp-includes/theme-previews.php
index d3f5c631c9b24..4c5b5500a7fbb 100644
--- a/src/wp-includes/theme-previews.php
+++ b/src/wp-includes/theme-previews.php
@@ -75,6 +75,36 @@ function wp_block_theme_activate_nonce() {
 	<?php
 }
 
+/**
+ * Add `_doing_it_wrong()` notice if the theme is requested before `pluggable.php` is loaded.
+ *
+ * @since 6.3.2
+ * @param string $current The current theme's stylesheet or template path.
+ * @return string Return the current theme's stylesheet or template path as is.
+ */
+function wp_theme_preview_maybe_doing_it_wrong( $current ) {
+	if ( ! empty( $_GET['wp_theme_preview'] ) && ! function_exists( 'wp_get_current_user' ) ) {
+		if ( current_filter() === 'template' ) {
+			$function_name = 'get_template()';
+		} else {
+			$function_name = 'get_stylesheet()';
+		}
+
+		_doing_it_wrong(
+			$function_name,
+			sprintf(
+				/* translators: translators: Developer debugging message. 1: PHP function name */
+				__( 'Calling %s before pluggable.php has loaded can result in getting the current theme instead of the previewed theme. Please ensure that you are using these functions after the plugins_loaded action has fired if this is not intended.' ),
+				$function_name
+			),
+			'6.3.2'
+		);
+	}
+	return $current;
+}
+add_filter( 'stylesheet', 'wp_theme_preview_maybe_doing_it_wrong' );
+add_filter( 'template', 'wp_theme_preview_maybe_doing_it_wrong' );
+
 /**
  * Add filters and actions to enable Block Theme Previews in the Site Editor.
  *