xml-pipeline/agentserver/message_bus/steps/xsd_validation.py
2026-01-08 15:35:36 -08:00

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2.2 KiB
Python

"""
xsd_validation.py — Validate the extracted payload against the listener-specific XSD.
After payload_extraction_step isolates the payload_tree and provenance,
this step validates the payload against the XSD that was auto-generated
from the listener's @xmlify dataclass at registration time.
The XSD is cached and pre-loaded. The schema object is injected into
state.metadata["schema"] when the listener's pipeline is built.
Failure here means the payload violates the declared contract — we collect
detailed errors for diagnostics.
Part of AgentServer v2.1 message pump.
"""
from lxml import etree
from agentserver.message_bus.message_state import MessageState
async def xsd_validation_step(state: MessageState) -> MessageState:
"""
Validate state.payload_tree against the listener's cached XSD schema.
Requires:
- state.payload_tree set
- state.metadata["schema"] containing a pre-loaded etree.XMLSchema
On success: payload is guaranteed to match the contract
On failure: state.error contains detailed validation messages
"""
if state.payload_tree is None:
state.error = "xsd_validation_step: no payload_tree (previous extraction failed)"
return state
schema = state.metadata.get("schema")
if schema is None:
state.error = "xsd_validation_step: no XSD schema in metadata (listener pipeline misconfigured)"
return state
if not isinstance(schema, etree.XMLSchema):
state.error = "xsd_validation_step: metadata['schema'] is not an XMLSchema object"
return state
try:
# assertValid raises DocumentInvalid with full error log
schema.assertValid(state.payload_tree)
except etree.DocumentInvalid:
# Collect all errors for clear diagnostics
error_lines = []
for error in schema.error_log:
error_lines.append(f"{error.level_name}: {error.message} (line {error.line})")
state.error = "xsd_validation_step: payload failed contract validation\n" + "\n".join(error_lines)
except Exception as exc: # pylint: disable=broad-except
state.error = f"xsd_validation_step: unexpected error during validation: {exc}"
return state