By catch on
Change record status: 
Published (View all published change records)
Project: 
Drupal core
Introduced in branch: 
9.3.x
Introduced in version: 
9.3.0-alpha1
Issue links: 
https://www.drupal.org/node/3225328
Description: 

Cache tags and contexts were always sorted regardless of usage, in order to make debugging and testing more convenient, however this added a performance burden to every HTML request.

In general this will not affect any runtime code at all, however some tests may need to account for differently sorted tags/contexts, in most cases the change will look like the following:

Before:

  $this->assertEquals($expected_top_level_contexts, $element['#cache']['contexts'], 'Expected cache contexts found.');

After:

    $this->assertEqualsCanonicalizing($expected_top_level_contexts, $element['#cache']['contexts'], 'Expected cache contexts found.');
Impacts: 
Module developers
Updates Done (doc team, etc.)
Online documentation: 
Not done
Theming guide: 
Not done
Module developer documentation: 
Not done
Examples project: 
Not done
Coder Review: 
Not done
Coder Upgrade: 
Not done
Other: 
Other updates done