Assertion error when foreign key reference to undeclared table

[CBroz1]

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Bug Report

Description

When using a foreign key reference of a table that is in the context namespace, but not declared, I hit this assertion error for QueryExpression.support.

Reproducibility

• OS: MACOS
• Python Version: 3.9.13
• MySQL Version: 8.0.28
• MySQL Deployment Strategy: remote
• DataJoint Version: 0.14.0
• Minimum number of steps to reliably reproduce the issue:

import datajoint as dj
from element_lab import lab
from element_lab.lab import Lab

db_prefix = dj.config["custom"].get("database.prefix", "")
schema = dj.schema(db_prefix + "example")

# lab.activate(db_prefix + "lab") # Forgetting this line results in vague assertion error

@schema
class Example(dj.Manual):
    definition = """
    -> Lab
    """

• Error stack

Expected Behavior

Increased error specificity would help new users navigate our design pattern of deferred activation. I'd propose adding to this block in compile_foreign_key.

    if isinstance(ref, type) and issubclass(ref, Table):
        ref = ref()
        try:
            _ = ref.support
        except AssertionError:
            raise DataJointError(
                f"Could not initialize this table as a foreign key reference: {result.ref_table}.\n"
                + "Does this schema need to be activated?"
            )

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Additional Research and Context

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