Inconsistent handling of errors for non-activated `UserTable`s

[iamamutt]

Bug Report

Description

Calling class methods, properties, or instance methods derived from parent classes of UserTable creates inconsistent and confusing error messages when schema is not activated for a set of tables.

import datajoint as dj

dj.config["loglevel"] = "INFO"
schema = dj.Schema()


@schema
class TableA(dj.Manual):
    definition = """
    # TableA example
    table_a : UUID
    ---
    label : VARCHAR(100)
    """


# printing of some properties is ok:
print(TableA.definition)  # ok -> No error.

#   # TableA example
#     table_a : UUID
#     ---
#     label : VARCHAR(100)


# Error description is valid for these cases:
TableA().describe()  # ok -> DataJointError: Class TableA is not properly declared (schema decorator not applied?)

TableA.describe()  # ok -> DataJointError: Class TableA is not properly declared (schema decorator not applied?)

# Uninformative error:
TableA()  # bad -> AttributeError: 'NoneType' object has no attribute 'non_blobs'


# Additional situations of inconsistent errors when printing from an non-activated `Table`.


@schema
class TableB(dj.Manual):
    definition = """
    thing : INT
    ----
    label : VARCHAR(200)
    """


instance = TableB()

# ok -> no error
print(TableB.definition)

#    thing : INT
#    ---
#    label : VARCHAR(200)

# preview.py:51, AttributeError: 'NoneType' object has no attribute 'non_blobs'
instance

# condition.py:154, AttributeError: 'NoneType' object has no attribute 'names'
instance & {}

# expression.py:96, AttributeError: 'NoneType' object has no attribute 'primary_key'
instance.fetch("KEY")

# expression.py:96, AttributeError: 'NoneType' object has no attribute 'primary_key'
instance.head()
TableB.head()

# condition.py:75, AttributeError: 'NoneType' object has no attribute 'secondary_attributes'
TableB & TableA

# issues with `__repr__`` and `_repr_html_`
# preview.py:8, AttributeError: 'NoneType' object has no attribute 'non_blobs'
instance.head
TableB.head


dj.config["loglevel"] = "DEBUG"

# ok -> <bound method QueryExpression.head of <__main__.TableB object at 0x1231b3cd0>>
instance.head

# diff error than before (closer to indication about activation) -> # expression.py:96, AttributeError: 'NoneType' object has no attribute 'primary_key'
instance.head()

[guzman-raphael]

Thanks for the report @iamamutt! :handshake:

This does seem like unintentional behavior although it doesn't seem like it would be too much to patch.