Bug_197_EVALUATE: CHAT-BOUNDARY-014 — vendor_id=None in _call_get_vendor_details propagates to DB layer with no clean error response

[steadhac]

Component: finbot/agents/chat.py → VendorChatAssistant._call_get_vendor_details (line 660)

Root cause:

# chat.py line 660-661
async def _call_get_vendor_details(self, vendor_id: int) -> str:
    result = await get_vendor_details(vendor_id, self.session_context)

vendor_id is forwarded directly to get_vendor_details with no None check.
When the LLM passes null for the field, vendor_id=None reaches the DB layer.
The DB driver raises TypeError (or a SQLAlchemy error), which propagates uncaught
out of the agent method — no error JSON is returned.

Steps to reproduce:

1. Mock get_vendor_details to raise TypeError when called with None.
2. Call agent._call_get_vendor_details(vendor_id=None).

Expected: {"error": "vendor_id is required"} — clean error JSON
Actual: TypeError propagates uncaught

How to execute:

pytest tests/unit/agents/test_chat_assistant.py::TestBoundaryAndTypeValues::test_chat_boundary_014_get_vendor_details_vendor_id_none_propagates -v

Proposed fix:

async def _call_get_vendor_details(self, vendor_id: int) -> str:
    if vendor_id is None:
        return json.dumps({"error": "vendor_id is required"})
    result = await get_vendor_details(vendor_id, self.session_context)
    ...

Impact: A vendor-facing chat session that triggers this path receives a 500-class
error instead of a structured message. The same pattern (no None guard before the DB
call) likely applies to _call_get_invoice_details, _call_get_vendor_invoices,
_call_get_vendor_payment_summary, and _call_get_vendor_contact_info — all of which
forward their vendor_id or invoice_id parameter directly.

Acceptance criteria:

• test_chat_boundary_014_get_vendor_details_vendor_id_none_propagates updated to assert error JSON
• _call_get_vendor_details returns {"error": ...} when vendor_id is None
• Audit _call_get_invoice_details, _call_get_vendor_invoices, _call_get_vendor_payment_summary, _call_get_vendor_contact_info for the same gap