[wp-trac] [WordPress Trac] #43003: HTML5 "required" attribute in Widget form() fails in ajax-actions.php during save

[WordPress Trac]

#43003: HTML5 "required" attribute in Widget form() fails in ajax-actions.php
during save
--------------------------+-----------------------------
 Reporter:  Andy Schmidt  |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  Widgets       |    Version:  4.9.1
 Severity:  normal        |   Keywords:
  Focuses:                |
--------------------------+-----------------------------
 If a field on a widget settings form uses the HTML5 "required" attribute,
 then saving the settings will only APPEAR to have "saved" the form
 content.

 In reality, the result is:
 {{{
 Undefined index: widgetbaseid-nn in wp-admin\includes\ajax-actions.php on
 line 1998
 Stack trace:
 1. {main}() E:\Hosted Sites\wwwroot\wp-admin\admin-ajax.php:0
 2. do_action() E:\Hosted Sites\wwwroot\wp-admin\admin-ajax.php:97
 3. WP_Hook->do_action() E:\Hosted Sites\wwwroot\wp-includes\plugin.php:453
 4. WP_Hook->apply_filters() E:\Hosted Sites\wwwroot\wp-includes\class-wp-
 hook.php:310
 5. wp_ajax_save_widget() E:\Hosted Sites\wwwroot\wp-includes\class-wp-
 hook.php:286
 }}}

 Simply removing the "required" attribute from this input field, will
 circumvent the bug:
 {{{#!php
 <?php
         <input class="widefat" type="text" required="required" id="<?php
 echo \esc_attr( $this->get_field_id( 'addtlfld' ) ); ?>" name="<?php echo
 \esc_attr( $this->get_field_name( 'addtlfld' ) ); ?>" value="<?php echo
 \esc_attr( $old_settings[ 'addtlfld' ] ?? '' ); ?>">
 }}}

 Attached is a plugin with two versions of the widget - one has regular
 text field, the other has the same text field but uses the "required"
 attribute.
 Uses PHP 7.1 syntax.

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Ticket URL: <https://core.trac.wordpress.org/ticket/43003>
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