Neo field blocks not appearing in entry editor after migration

[romainpoirier]

Bug Description

After migrating the site from Craft CMS 3 to 4 and then to 5, newly added blocks in a Neo field do not appear in the entry editor view, even though they are visible in the field configuration view. Clearing the caches, re-saving the field, rebuilding the project config, and re-saving the Neo block does not resolve the issue.

Steps to reproduce

1. Use the following versions:
   "craftcms/cms": "5.8.21"
"spicyweb/craft-neo": "5.5.3"
2. Migrate a Neo field from Craft CMS 3 to 4, then to 5.
3. Add new blocks to the Neo field.
4. Go to the entry editor and observe that the new blocks are not displayed for encoding, despite appearing in the field configuration.

Expected behaviour

The newly added Neo blocks should be visible and available for encoding in the entry editor, as expected after re-saving the field and rebuilding the project config.

Neo version

5.5.3

Craft CMS version

5.8.21

What is the affected Neo field's propagation method?

No response

Does this issue involve templating, and if so, is eager-loading used?

This is not a templating issue

[ttempleton]

In the Section block type settings, is the Code checkbox checked in the list of allowed child block types?

[romainpoirier]

Indeed, the "Code" option was unchecked. Thanks for the reminder, I missed it.

Why is explicit activation required if the block is already a child of Section? Wouldn’t it make sense for activation to be automatic when a field is added?

In which common scenario would a child block be created, added to the parent, but never used?

[ttempleton]

Fair point, we'll consider making that change.