Plone 5 & Plone 6 - Adding key/value to dict in portal_registry fails

[fabiSwDevBeg]

Problem

When editing a registry entry of type dict in the Control Panel (portal_registry), attempting to add a new key/value pair closes the edit modal but the new pair is not saved. This happens both on Plone 5 and Plone 6.

Steps to reproduce

1. Open the Plone site Control Panel.
2. Open the Configuration Registry (portal_registry) control panel.
3. Select an entry whose value is a dict (for example your.package.interfaces.IMySettings.some_dict).
4. Open the edit modal, click Add.

Expected behavior
A new entry for the Dict should appear in the modal and i should be able to edit it.

Actual behavior
The modal closes immediately after saving, but the new entry is not added — the dict remains unchanged.

Environment

• Plone version: 5.x and 6.x (both affected) (4.x not tested)
• Python version: 3.8 / 3.10

[ujsquared]

Here's what I found,

1. If you look at the code here

    field_type = schema.Choice(
        title="Field Type",
        vocabulary=SimpleVocabulary.fromValues(
            [
                "Bytes",
                "BytesLine",
                "ASCII",
                "ASCIILine",
                "Text",
                "TextLine",
                "Bool",
                "Int",
                "Float",
                "Decimal",
                "Password",
                "Datetime",
                "Date",
                "Timedelta",
                "SourceText",
                "URI",
                "Id",
                "DottedName",
                # XXX not supporting these types yet as it requires additional config
                # 'Tuple', 'List', 'Set', 'FrozenSet', 'Dict',
            ]

Records in registry don't support Dict by default now. Maybe it's the support from z3c.form to render multipart form for dicts that's making it look like a bug instead. Only thing missing to make this work should be the relevant plone.app.z3cform connectors/connecting functions. I can be wrong though.

@davisagli @jensens can provide more information.