field.purge.inc points to php.net delete function

I don't think that's the best way.

Adding the class name is better: FieldItemInterface::delete(). Though probably needs to be the fully qualified classname, I'm not sure.

Adding patch

+++ b/core/modules/field/field.purge.inc
@@ -21,9 +21,9 @@
+ * - Invoking the @link \Drupal\Core\Field\FieldItemListInterface::delete() FieldItemListInterface delete() @endlink
+ *   method for each field on the entity. A file field type might use this
+ *   method to delete uploaded files from the filesystem.

I think we can change this to: "Invoking the method \Drupal\Core\Field\FieldItemListInterface::delete() for each field on the entity. A file field type might use this method to delete uploaded files from the filesystem."

@daffie, updated the patch as per your suggestion.

Getting there, but it needs to wrap to 80 chars.

Also, we possibly don't need the @link at all, come to think of it. IIRC a fully-qualified method will automatically link.

Adding changes as per suggestion #11

Two remarks:

1. +++ b/core/modules/field/field.purge.inc
   @@ -4,7 +4,6 @@
   -
   
   @@ -106,7 +105,7 @@ function field_purge_batch($batch_size, $field_storage_uuid = NULL) {
   -  $deleted_storages = \Drupal::state()->get('field.storage.deleted') ?: array();
   +  $deleted_storages = \Drupal::state()->get('field.storage.deleted') ? : array();
   

   These changes do not belong in this issue.

2. +++ b/core/modules/field/field.purge.inc
   @@ -21,9 +20,9 @@
   + *   each field on the entity. A file field type might use this method to delete ¶
   

   This line has an added space at of the line. Please remove it.

Changes done as suggested at #13

It looks good to me.
For me it is RTBC.

For the committer: Please ignore the first hunk of the patch with the unnecessary removal of a empty line.

Committed and pushed 4338fa0 to 8.3.x and 719c20a to 8.2.x. Thanks!

As a docs patch this is rc eligible and therefore can be committed to 8.2.x

+++ b/core/modules/field/field.purge.inc
@@ -4,7 +4,6 @@
-

This is not correct and is totally out-of-scope for this issue. Reverted on commit.