[wp-trac] [WordPress Trac] #42548: Widgets: Populate global $post with queried object on singular queries instead of nullifying it

[WordPress Trac]

#42548: Widgets: Populate global $post with queried object on singular queries
instead of nullifying it
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 Reporter:  westonruter   |      Owner:
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  4.9
Component:  Widgets       |    Version:  4.9
 Severity:  normal        |   Keywords:
  Focuses:                |
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 Until 4.9, if a plugin did `add_filter( 'widget_text', 'do_shortcode' )`
 and they added a `[gallery]` to a widget that is displayed on a singular
 template, then the gallery would (usually) show the attachments from the
 current queried post. This behavior changed in #10457 for 4.9 whereby the
 global `$post` is nullified to ensure that the Text widget renders
 consistently across whatever template it may appear (singular, archive,
 404, etc).

 There are two problems with this:

 1. When `$post` is `null`, then the gallery shortcode will list out all
 attachments from the media library. This could be embarrassing or at least
 undesired.
 2. If a site previously did rely on being able to render a gallery of
 attached images for the current post in the sidebar, this is broken.

 I think we can fix both of these issues simply by checking if
 `is_singular()` and if so, set the `$post` to the current queried object
 (`get_queried_object()`). This will ensure that the global `$post` isn't
 coming from an unpredictable source (such as a previous query that failed
 to call `wp_reset_postdata()`), which was a primary motivator for
 nullifying the global `$post` to begin with.

 This same approach can be done for the Custom HTML widget, which currently
 doesn't nullify `$post` even though it does apply `widget_text` filters
 (though not for shortcodes in core).

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Ticket URL: <https://core.trac.wordpress.org/ticket/42548>
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