[wp-trac] [WordPress Trac] #39693: Fix missing assignment of widgets on theme switch

[WordPress Trac]

#39693: Fix missing assignment of widgets on theme switch
----------------------------------------+------------------------
 Reporter:  melchoyce                   |       Owner:  obenland
     Type:  enhancement                 |      Status:  reviewing
 Priority:  high                        |   Milestone:  4.9
Component:  Widgets                     |     Version:
 Severity:  normal                      |  Resolution:
 Keywords:  has-unit-tests needs-patch  |     Focuses:
----------------------------------------+------------------------
Changes (by westonruter):

 * keywords:  has-patch has-unit-tests => has-unit-tests needs-patch


Comment:

 @obenland I'm able to reproduce PHP warnings when switching between Twenty
 Seventeen and Twenty Fifteen, see conversation at
 https://wordpress.slack.com/archives/C0381N237/p1506163588000022

 Here are the warnings and where they happen:

 > Warning: Invalid argument supplied for foreach() in /srv/www/wordpress-
 develop/public_html/src/wp-includes/widgets.php on line 1318

 Line in question:

 {{{
 // ...for every widget we're trying to revive.
 foreach ( $old_widgets as $key => $widget_id )
 }}}

 Also:

 > Warning: array_merge(): Argument #1 is not an array in /srv/www
 /wordpress-develop/public_html/src/wp-includes/widgets.php on line 1156

 At:

 {{{
 // Find hidden/lost multi-widget instances.
 $shown_widgets = call_user_func_array( 'array_merge', $sidebars_widgets );
 }}}

 And on the next line:

 > Warning: array_diff(): Argument #2 is not an array in /srv/www
 /wordpress-develop/public_html/src/wp-includes/widgets.php on line 1157

 At:

 {{{
 $lost_widgets  = array_diff( $registered_widgets_ids, $shown_widgets );
 }}}

 And two lines below:

 > Warning: Invalid argument supplied for foreach() in /srv/www/wordpress-
 develop/public_html/src/wp-includes/widgets.php on line 1159

 {{{
 foreach ( $lost_widgets as $key => $widget_id ) {
 }}}

 And lastly:
 > Warning: array_merge(): Argument #1 is not an array in /srv/www
 /wordpress-develop/public_html/src/wp-includes/widgets.php on line 1167

 At:

 {{{
 $sidebars_widgets['wp_inactive_widgets'] = array_merge( $lost_widgets,
 (array) $sidebars_widgets['wp_inactive_widgets'] );
 }}}

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Ticket URL: <https://core.trac.wordpress.org/ticket/39693#comment:112>
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