schema: unexpected handling of lists in records config

[MSusik]

Recently I encountered a problem with JSONAlchemy config (.cfg) files. I wanted to create a field which should be a list of strings inside the record. Here is the definition:

schema:
        {'emails': {'type': 'list', 'force': True, 'schema': {'type': 'string'}}}

When there is no key emails in the dictionary handled to Record.create method, I obtain:

>>> rec['emails']
[{'type': None}]

It seems that JSONAlchemy always understands schema as a base for a dictionary. Other than that, it works fine.

I can make it working by defining the field as:

schema:
        {'emails': {'type': 'list', 'force': True, 'items': {'type': 'string'}}}

But in this case I can't pass the validation, as Cerberus expects dictionaries inside the list.

https://cerberus.readthedocs.org/en/latest/#items-list
https://cerberus.readthedocs.org/en/latest/#schema-list
Please note that Cerberus' documentation is not complete.

What to do?

[MSusik]

Continuation of inveniosoftware/invenio#2599