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HTML API: Join text nodes on invalid-tag-name boundaries.
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A fix was introduced to the Tag Processor to ensure that contiguous text
in an HTML document emerges as a single text node spanning the full
sequence. Unfortunately, that patch was marginally over-zealous in
checking if a "<" started a syntax token or not. It used the following:

{{{
<?php
if ( 'A' <= $c && 'z' >= $c ) { ... }
}}}

This was based on the assumption that the A-Z and a-z letters are
contiguous in the ASCII range; they aren't, and there's a gap of
several characters in between. The result of this is that in some
cases the parser created a text boundary when it didn't need to.
Text boundaries can be surprising and can be created when reaching
invalid syntax, HTML comments, and more hidden elements, so
semantically this wasn't a major bug, but it was an aesthetic
challenge.

In this patch the check is properly compared for both upper- and
lower-case variants that could potentially form tag names.

{{{
<?php
if ( ( 'A' <= $c && 'Z' >= $c ) || ( 'a' <= $c && 'z' >= $c ) ) { ... }
}}}

This solves the problem and ensures that contiguous text appears
as a single text node when scanning tokens.

Developed in #6041
Discussed in https://core.trac.wordpress.org/ticket/60385

Follow-up to [57489]
Props dmsnell, jonsurrell
Fixes #60385



git-svn-id: https://develop.svn.wordpress.org/trunk@57542 602fd350-edb4-49c9-b593-d223f7449a82
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dmsnell committed Feb 6, 2024
1 parent a0fedc9 commit b7027a8
Showing 1 changed file with 12 additions and 6 deletions.
18 changes: 12 additions & 6 deletions src/wp-includes/html-api/class-wp-html-tag-processor.php
Original file line number Diff line number Diff line change
Expand Up @@ -1528,20 +1528,26 @@ private function parse_next_tag() {

if ( $at > $was_at ) {
/*
* A "<" has been found in the document. That may be the start of another node, or
* it may be an "ivalid-first-character-of-tag-name" error. If this is not the start
* of another node the "<" should be included in this text node and another
* termination point should be found for the text node.
* A "<" normally starts a new HTML tag or syntax token, but in cases where the
* following character can't produce a valid token, the "<" is instead treated
* as plaintext and the parser should skip over it. This avoids a problem when
* following earlier practices of typing emoji with text, e.g. "<3". This
* should be a heart, not a tag. It's supposed to be rendered, not hidden.
*
* At this point the parser checks if this is one of those cases and if it is
* will continue searching for the next "<" in search of a token boundary.
*
* @see https://html.spec.whatwg.org/#tag-open-state
*/
if ( strlen( $html ) > $at + 1 ) {
$next_character = $html[ $at + 1 ];
$at_another_node =
$at_another_node = (
'!' === $next_character ||
'/' === $next_character ||
'?' === $next_character ||
( 'A' <= $next_character && $next_character <= 'z' );
( 'A' <= $next_character && $next_character <= 'Z' ) ||
( 'a' <= $next_character && $next_character <= 'z' )
);
if ( ! $at_another_node ) {
++$at;
continue;
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