Update JSON flags and comments

Aligns with WordPress/wordpress-develop#6520

lib/experimental/script-modules.php

@@ -255,36 +255,24 @@ function gutenberg_print_script_module_data(): void {
  * - JSON_HEX_TAG: All < and > are converted to \u003C and \u003E.
  * - JSON_UNESCAPED_SLASHES: Don't escape /.
  *
+ * If the page will use UTF-8 encoding, it's safe to print unescaped unicode:
+ *
+ * - JSON_UNESCAPED_UNICODE: Encode multibyte Unicode characters literally (instead of as `\uXXXX`).
+ * - JSON_UNESCAPED_LINE_TERMINATORS: The line terminators are kept unescaped when
+ * JSON_UNESCAPED_UNICODE is supplied. It uses the same behaviour as it was
+ * before PHP 7.1 without this constant. Available as of PHP 7.1.0.
+ *
+ * The JSON specification requires encoding in UTF-8, so if the generated HTML page
+ * is not encoded in UTF-8 then it's not safe to include those literals. They must
+ * be escaped to avoid encoding issues.
+ *
+ * @see https://www.rfc-editor.org/rfc/rfc8259.html for details on encoding requirements.
  * @see https://www.php.net/manual/en/json.constants.php for details on these constants.
- * @see https://html.spec.whatwg.org/#script-data-state for details on script
- * tag parsing.
+ * @see https://html.spec.whatwg.org/#script-data-state for details on script tag parsing.
  */
- $json_encode_flags = JSON_HEX_TAG | JSON_UNESCAPED_SLASHES;
- if ( 'UTF-8' === get_option( 'blog_charset' ) ) {
- /*
- * If the page will use UTF-8 encoding, it's safe to print unescaped unicode in
- * JSON. Set the following flags:
- *
- * - JSON_UNESCAPED_UNICODE: Encode multibyte Unicode characters literally
- * (default is to escape as \uXXXX).
- * - JSON_UNESCAPED_LINE_TERMINATORS: The line terminators are kept unescaped when
- * JSON_UNESCAPED_UNICODE is supplied. It uses the same behaviour as it was
- * before PHP 7.1 without this constant. Available as of PHP 7.1.0.
- *
- * The JSON specification does not specify a character encoding, RFC-8259
- * suggests that UTF-8 be used everywhere. It's risky to print unicode if the page
- * uses any other encoding.
- *
- * > JSON text exchanged between systems that are not part of a closed ecosystem
- * > MUST be encoded using UTF-8. Previous specifications of JSON have not required
- * > the use of UTF-8 when transmitting JSON text. However, the vast majority of
- * > JSON- based software implementations have chosen to use the UTF-8 encoding,
- * > to the extent that it is the only encoding that achieves interoperability.
- *
- * @see https://www.rfc-editor.org/rfc/rfc8259.html
- *
- */
- $json_encode_flags |= JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_LINE_TERMINATORS;
+ $json_encode_flags = JSON_HEX_TAG | JSON_UNESCAPED_SLASHES | JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_LINE_TERMINATORS;
+ if ( 'UTF-8' !== get_option( 'blog_charset' ) ) {
+ $json_encode_flags = JSON_HEX_TAG | JSON_UNESCAPED_SLASHES;
  }
 
  wp_print_inline_script_tag(