Hallo editor does not work in StructBlock

[cnk]

I upgraded an old Wagtail project to test Wagtail 2.13rc1 and found that text is not rendered into the Hallo.js rich text editor if the editor is part of a StructBlock. The editor behaves just fine if it is used in its own RichTextField.

Steps to Reproduce

I created a minimal repository to demostrate this issue: https://github.com/cnk/hallo-issue I have included the sqlite database in the repository so you should be able to see this in action by:

1. check out https://github.com/cnk/hallo-issue
2. Activate a virtual environment and pip install -r requirements.txt
3. ./manage.py createsuperuser
4. ./manage.py runserver

Technical details

• Python version: I used 3.7.7
• Django version: 3.2
• Wagtail version: 2.13rc1
• Browser version: I tried it with Firefox and Chrome.