[wp-trac] [WordPress Trac] #64609: HTML API: set_modifiable_text() ignores leading newlines in PRE, LISTING, TEXTAREA

[WordPress Trac]

#64609: HTML API: set_modifiable_text() ignores leading newlines in PRE, LISTING,
TEXTAREA
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 Reporter:  jonsurrell                |       Owner:  jonsurrell
     Type:  defect (bug)              |      Status:  assigned
 Priority:  normal                    |   Milestone:  7.0
Component:  HTML API                  |     Version:  6.7
 Severity:  minor                     |  Resolution:
 Keywords:  has-patch has-unit-tests  |     Focuses:
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Comment (by ozgursar):

 == Patch Testing Report

 Patch Tested: https://github.com/WordPress/wordpress-develop/pull/11062

 === Environment
 - WordPress: 7.0-beta1-61709-src
 - PHP: 8.2.29
 - Server: nginx/1.29.4
 - Database: mysqli (Server: 8.4.7 / Client: mysqlnd 8.2.29)
 - Browser: Chrome 145.0.0.0
 - OS: macOS
 - Theme: Twenty Twenty-Five 1.4
 - MU Plugins: None activated
 - Plugins:
   * Code Snippets 3.9.5
   * Test Reports 1.2.1

 === Steps taken
 1. Add the following test snippet via `functions.php` or `Code Snippets
 plugin` to create a shortcode


 {{{
 add_shortcode( 'patch_test_64609', function() {
     $out = '';

     // textarea via WP_HTML_Processor
     $p = WP_HTML_Processor::create_fragment( '<textarea></textarea>' );
     $p->next_token();
     $p->set_modifiable_text( "\nAFTER NEWLINE" );
     $out .= $p->get_updated_html();

     // pre and listing via WP_HTML_Tag_Processor directly
     foreach ( [ 'pre', 'listing' ] as $tag ) {
         $p = new WP_HTML_Tag_Processor( "<$tag>existing text</$tag>" );
         $p->next_tag( $tag );
         $p->next_token();
         $p->set_modifiable_text( "\nAFTER NEWLINE" );
         $out .= $p->get_updated_html();
     }

     return $out;
 } );
 }}}


 2. Add the shortcode `[patch_test_64609]` to any page/post and view the
 generated HTML
 3. ✅ Patch is solving the problem

 === Expected result
 - For the `TEXTAREA` element `\n` is working as expected.
 - For `PRE` and `LISTING` elements there is no change (as also expected by
 comment #4)

 === Screenshots/Screencast with results
 Before
 [[Image(https://i.imgur.com/bkkCAm3.png)]]

 After
 [[Image(https://i.imgur.com/fQcNNQh.png)]]

-- 
Ticket URL: <https://core.trac.wordpress.org/ticket/64609#comment:5>
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