[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
--------------------------+------------------------
 Reporter:  jonsurrell    |      Owner:  jonsurrell
     Type:  defect (bug)  |     Status:  assigned
 Priority:  normal        |  Milestone:  7.0
Component:  HTML API      |    Version:  6.7
 Severity:  minor         |   Keywords:
  Focuses:                |
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 The `::set_modifiable_text()` method on `WP_HTML_Tag_Processor` and
 `WP_HTML_Processor` will fail to include a leading newline in the provided
 plaintext content on the first text of `TEXTAREA`, `PRE`, and `LISTING`
 elements.

 This is due to special rules for these elements that cause a single
 leading newline to be ignored immediately following the open tag.

 {{{#!php
 <?php
 $html_processor =
 WP_HTML_Processor::create_fragment('<textarea></textarea>');
 $html_processor->next_token();
 $html_processor->set_modifiable_text( "\nAFTER NEWLINE" );
 var_dump( $html_processor->get_modifiable_text() );
 // string(13) "AFTER NEWLINE"
 echo $html_processor->get_updated_html();
 /* Prints:
 <textarea>
 AFTER NEWLINE</textarea>
 */
 }}}

 Note that the newline is present in the updated HTML, however the HTML
 parsing rules cause the leading newline to be ignored.

 When rendered in the browser, this `TEXTAREA` element will report its
 `.textContent` as `AFTER NEWLINE` (with no leading newline) and the
 rendered element shows `AFTER NEWLINE` on the first line of the input box.

 In order for the `TEXTAREA` to begin with a newline in its content, an
 additional newline must be included.

 This is closely related to #64607.

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