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<dt style="float: left; width: 6em; font-weight: bold">Revision</dt> <dd><a style="font-weight: bold" href="https://core.trac.wordpress.org/changeset/60617">60617</a><script type="application/ld+json">{"@context":"http://schema.org","@type":"EmailMessage","description":"Review this Commit","action":{"@type":"ViewAction","url":"https://core.trac.wordpress.org/changeset/60617","name":"Review Commit"}}</script></dd>
<dt style="float: left; width: 6em; font-weight: bold">Author</dt> <dd>jonsurrell</dd>
<dt style="float: left; width: 6em; font-weight: bold">Date</dt> <dd>2025-08-07 08:31:07 +0000 (Thu, 07 Aug 2025)</dd>
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<pre style='padding-left: 1em; margin: 2em 0; border-left: 2px solid #ccc; line-height: 1.25; font-size: 105%; font-family: sans-serif'>HTML API: Reduce length checks in skip_script_data.

Apply an optimization to remove several repeated string length checks in `WP_HTML_Tag_Processor::skip_script_data()`.

Developed in https://github.com/WordPress/wordpress-develop/pull/9230.

Props jonsurrell, dmsnell.
See <a href="https://core.trac.wordpress.org/ticket/63738">#63738</a>.</pre>

<h3>Modified Paths</h3>
<ul>
<li><a href="#trunksrcwpincludeshtmlapiclasswphtmltagprocessorphp">trunk/src/wp-includes/html-api/class-wp-html-tag-processor.php</a></li>
<li><a href="#trunktestsphpunittestshtmlapiwpHtmlTagProcessorphp">trunk/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php</a></li>
</ul>

</div>
<div id="patch">
<h3>Diff</h3>
<a id="trunksrcwpincludeshtmlapiclasswphtmltagprocessorphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/src/wp-includes/html-api/class-wp-html-tag-processor.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/src/wp-includes/html-api/class-wp-html-tag-processor.php    2025-08-07 07:58:33 UTC (rev 60616)
+++ trunk/src/wp-includes/html-api/class-wp-html-tag-processor.php      2025-08-07 08:31:07 UTC (rev 60617)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1497,12 +1497,47 @@
</span><span class="cx" style="display: block; padding: 0 10px">                        $at += strcspn( $html, '-<', $at );
</span><span class="cx" style="display: block; padding: 0 10px"> 
</span><span class="cx" style="display: block; padding: 0 10px">                        /*
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+                         * Optimization: Terminating a complete script element requires at least eight
+                        * additional bytes in the document. Some checks below may cause local escaped
+                        * state transitions when processing shorter strings, but those transitions are
+                        * irrelevant if the script tag is incomplete and the function must return false.
+                        *
+                        * This may need updating if those transitions become significant or exported from
+                        * this function in some way, such as when building safe methods to embed JavaScript
+                        * or data inside a SCRIPT element.
+                        *
+                        *     $at may be here.
+                        *        ↓
+                        *     ...</script>
+                        *         ╰──┬───╯
+                        *     $at + 8 additional bytes are required for a non-false return value.
+                        *
+                        * This single check eliminates the need to check lengths for the shorter spans:
+                        *
+                        *           $at may be here.
+                        *                  ↓
+                        *     <script><!-- --></script>
+                        *                   ├╯
+                        *             $at + 2 additional characters does not require a length check.
+                        *
+                        * The transition from "escaped" to "unescaped" is not relevant if the document ends:
+                        *
+                        *           $at may be here.
+                        *                  ↓
+                        *     <script><!-- -->[[END-OF-DOCUMENT]]
+                        *                   ╰──┬───╯
+                        *             $at + 8 additional bytes is not satisfied, return false.
+                        */
+                       if ( $at + 8 >= $doc_length ) {
+                               return false;
+                       }
+
+                       /*
</ins><span class="cx" style="display: block; padding: 0 10px">                          * For all script states a "-->"  transitions
</span><span class="cx" style="display: block; padding: 0 10px">                         * back into the normal unescaped script mode,
</span><span class="cx" style="display: block; padding: 0 10px">                         * even if that's the current state.
</span><span class="cx" style="display: block; padding: 0 10px">                         */
</span><span class="cx" style="display: block; padding: 0 10px">                        if (
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                                $at + 2 < $doc_length &&
</del><span class="cx" style="display: block; padding: 0 10px">                                 '-' === $html[ $at ] &&
</span><span class="cx" style="display: block; padding: 0 10px">                                '-' === $html[ $at + 1 ] &&
</span><span class="cx" style="display: block; padding: 0 10px">                                '>' === $html[ $at + 2 ]
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1512,10 +1547,6 @@
</span><span class="cx" style="display: block; padding: 0 10px">                                continue;
</span><span class="cx" style="display: block; padding: 0 10px">                        }
</span><span class="cx" style="display: block; padding: 0 10px"> 
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                        if ( $at + 1 >= $doc_length ) {
-                               return false;
-                       }
-
</del><span class="cx" style="display: block; padding: 0 10px">                         /*
</span><span class="cx" style="display: block; padding: 0 10px">                         * Everything of interest past here starts with "<".
</span><span class="cx" style="display: block; padding: 0 10px">                         * Check this character and advance position regardless.
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1537,7 +1568,6 @@
</span><span class="cx" style="display: block; padding: 0 10px">                         * parsing after updating the state.
</span><span class="cx" style="display: block; padding: 0 10px">                         */
</span><span class="cx" style="display: block; padding: 0 10px">                        if (
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                                $at + 2 < $doc_length &&
</del><span class="cx" style="display: block; padding: 0 10px">                                 '!' === $html[ $at ] &&
</span><span class="cx" style="display: block; padding: 0 10px">                                '-' === $html[ $at + 1 ] &&
</span><span class="cx" style="display: block; padding: 0 10px">                                '-' === $html[ $at + 2 ]
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1561,7 +1591,6 @@
</span><span class="cx" style="display: block; padding: 0 10px">                         * proceed scanning to the next potential token in the text.
</span><span class="cx" style="display: block; padding: 0 10px">                         */
</span><span class="cx" style="display: block; padding: 0 10px">                        if ( ! (
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                                $at + 6 < $doc_length &&
</del><span class="cx" style="display: block; padding: 0 10px">                                 ( 's' === $html[ $at ] || 'S' === $html[ $at ] ) &&
</span><span class="cx" style="display: block; padding: 0 10px">                                ( 'c' === $html[ $at + 1 ] || 'C' === $html[ $at + 1 ] ) &&
</span><span class="cx" style="display: block; padding: 0 10px">                                ( 'r' === $html[ $at + 2 ] || 'R' === $html[ $at + 2 ] ) &&
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1579,9 +1608,6 @@
</span><span class="cx" style="display: block; padding: 0 10px">                         * "<script123" should not end a script region even though
</span><span class="cx" style="display: block; padding: 0 10px">                         * "<script" is found within the text.
</span><span class="cx" style="display: block; padding: 0 10px">                         */
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                        if ( $at + 6 >= $doc_length ) {
-                               continue;
-                       }
</del><span class="cx" style="display: block; padding: 0 10px">                         $at += 6;
</span><span class="cx" style="display: block; padding: 0 10px">                        $c   = $html[ $at ];
</span><span class="cx" style="display: block; padding: 0 10px">                        if ( ' ' !== $c && "\t" !== $c && "\r" !== $c && "\n" !== $c && '/' !== $c && '>' !== $c ) {
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1611,8 +1637,6 @@
</span><span class="cx" style="display: block; padding: 0 10px">                                }
</span><span class="cx" style="display: block; padding: 0 10px"> 
</span><span class="cx" style="display: block; padding: 0 10px">                                if ( $this->bytes_already_parsed >= $doc_length ) {
</span><del style="background-color: #fdd; text-decoration:none; display:block; padding: 0 10px">-                                        $this->parser_state = self::STATE_INCOMPLETE_INPUT;
-
</del><span class="cx" style="display: block; padding: 0 10px">                                         return false;
</span><span class="cx" style="display: block; padding: 0 10px">                                }
</span><span class="cx" style="display: block; padding: 0 10px"> 
</span></span></pre></div>
<a id="trunktestsphpunittestshtmlapiwpHtmlTagProcessorphp"></a>
<div class="modfile"><h4 style="background-color: #eee; color: inherit; margin: 1em 0; padding: 1.3em; font-size: 115%">Modified: trunk/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php</h4>
<pre class="diff"><span>
<span class="info" style="display: block; padding: 0 10px; color: #888">--- trunk/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php 2025-08-07 07:58:33 UTC (rev 60616)
+++ trunk/tests/phpunit/tests/html-api/wpHtmlTagProcessor.php   2025-08-07 08:31:07 UTC (rev 60617)
</span><span class="lines" style="display: block; padding: 0 10px; color: #888">@@ -1982,6 +1982,49 @@
</span><span class="cx" style="display: block; padding: 0 10px">        }
</span><span class="cx" style="display: block; padding: 0 10px"> 
</span><span class="cx" style="display: block; padding: 0 10px">        /**
</span><ins style="background-color: #dfd; text-decoration:none; display:block; padding: 0 10px">+         * Test that script tags are parsed correctly.
+        *
+        * Script tag parsing is very complicated, see the following resources for more details:
+        *
+        * - https://html.spec.whatwg.org/multipage/parsing.html#script-data-state
+        * - https://html.spec.whatwg.org/multipage/scripting.html#restrictions-for-contents-of-script-elements
+        *
+        * @ticket 63738
+        *
+        * @dataProvider data_script_tag
+        */
+       public function test_script_tag_parsing( string $input, bool $closes ) {
+               $processor = new WP_HTML_Tag_Processor( $input );
+
+               if ( $closes ) {
+                       $this->assertTrue( $processor->next_token(), 'Expected to find complete script tag.' );
+                       $this->assertSame( 'SCRIPT', $processor->get_tag() );
+                       return;
+               }
+
+               $this->assertFalse( $processor->next_token(), 'Expected to fail next_token().' );
+               $this->assertTrue( $processor->paused_at_incomplete_token(), 'Expected an incomplete SCRIPT tag token.' );
+       }
+
+       /**
+        * Data provider.
+        */
+       public static function data_script_tag(): array {
+               return array(
+                       'Basic script tag'                          => array( '<script></script>', true ),
+                       'Script with type attribute'                => array( '<script type="text/javascript"></script>', true ),
+                       'Script data escaped'                       => array( '<script><!--</script>', true ),
+                       'Script data double-escaped exit (comment)' => array( '<script><!--<script>--></script>', true ),
+                       'Script data double-escaped exit (closed)'  => array( '<script><!--<script></script></script>', true ),
+                       'Script data double-escaped exit (closed/truncated)' => array( '<script><!--<script></script </script>', true ),
+                       'Script data no double-escape'              => array( '<script><!-- --><script></script>', true ),
+
+                       'Script tag with self-close flag (ignored)' => array( '<script />', false ),
+                       'Script data double-escaped'                => array( '<script><!--<script></script>', false ),
+               );
+       }
+
+       /**
</ins><span class="cx" style="display: block; padding: 0 10px">          * Invalid tag names are comments on tag closers.
</span><span class="cx" style="display: block; padding: 0 10px">         *
</span><span class="cx" style="display: block; padding: 0 10px">         * @ticket 58007
</span></span></pre>
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