[wp-trac] [WordPress Trac] #55586: `get_block_wrapper_attributes` generates PHP notices.

[WordPress Trac]

#55586: `get_block_wrapper_attributes` generates PHP notices.
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 Reporter:  jmichaelward  |      Owner:  (none)
     Type:  defect (bug)  |     Status:  new
 Priority:  normal        |  Milestone:  Awaiting Review
Component:  General       |    Version:
 Severity:  normal        |   Keywords:
  Focuses:                |
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 To replicate this issue:

 1. Set both `WP_DEBUG` and `WP_DEBUG_LOG` in wp-config.php to `true` so
 that errors will be logged to `wp-content/debug.log`.
 2. Using WP-CLI, run `wp shell`.
 3. Call `get_block_wrapper_attributes();` in the terminal.
 4. Note the errors and call stack output in `wp-content/debug.log`. It
 will look something like this:

 [18-Apr-2022 16:05:27 UTC] PHP Notice:  Trying to access array offset on
 value of type null in wp-includes/class-wp-block-supports.php on line 94
 [18-Apr-2022 16:05:27 UTC] PHP Notice:  Trying to access array offset on
 value of type null in wp-includes/class-wp-block-supports.php on line 96

 `get_block_wrapper_attributes()` makes a singleton call to retrieve the
 `WP_Block_Supports` object, which in turn calls `apply_block_supports` on
 that object. The `apply_block_supports` method presumes that there is an
 editor block already assigned to the object, and attempts to retrieve the
 block type by using the `blockName` set on in the array of the
 `$block_to_render` property. Since the default value on the
 `WP_Block_Supports` object is `null`, this generates the error.

 It seems that the easiest solution here is to return an empty array from
 `apply_block_supports` if `$block_to_render` is not set. Since
 `get_block_wrapper_attributes` is a public function that does not accept a
 block, it can be called outside of a sequence where `WP_Block_Supports`
 might already have set properties on the object.

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Ticket URL: <https://core.trac.wordpress.org/ticket/55586>
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