Follow up for #1871772-108: Convert custom blocks to content entities
Problem/Motivation
+++ b/core/modules/block/custom_block/lib/Drupal/custom_block/CustomBlockFormController.php
@@ -0,0 +1,216 @@
+ // Override the default CSS class name, since the user-defined custom block
+ // type name in 'TYPE-block-form' potentially clashes with third-party class
+ // names.
+ $form['#attributes']['class'][0] = drupal_html_class('block-' . $block->type->value . '-form');
The BUNDLE_TYPE_form pattern is a massive anti-pattern from Node module in the first place.
Let's create a (major) follow-up issue to change that form ID pattern to prevent such namespace conflicts (for all entity types).
This is that discussion
Proposed resolution
Decide on a class naming pattern for entity forms and implement it
Remaining tasks
Write the patch