fix: enforce canonical weekly manifest wire

Co-Authored-By: Codex <noreply@openai.com>

Author: Pigbibi

src/political_event_tracking_research/weekly_manifest.py

@@ -30,12 +30,40 @@ def parse_weekly_manifest(value: Mapping[str, object]) -> WeeklySourceContract:
     return parse_weekly_contract(contract)
 
 
+def parse_weekly_manifest_bytes(wire: bytes) -> WeeklySourceContract:
+    if type(wire) is not bytes:
+        raise WeeklyContractError("manifest_wire_invalid")
+
+    def pairs(items: list[tuple[str, object]]) -> dict[str, object]:
+        result: dict[str, object] = {}
+        for key, item in items:
+            if key in result:
+                raise WeeklyContractError("manifest_duplicate_key")
+            result[key] = item
+        return result
+
+    try:
+        value = json.loads(wire.decode("utf-8"), object_pairs_hook=pairs)
+    except WeeklyContractError:
+        raise
+    except (UnicodeError, json.JSONDecodeError, TypeError, ValueError, RecursionError):
+        raise WeeklyContractError("manifest_wire_invalid") from None
+    if not isinstance(value, Mapping):
+        raise WeeklyContractError("manifest_shape_invalid")
+    contract = parse_weekly_manifest(value)
+    if serialize_weekly_manifest(contract) != wire:
+        raise WeeklyContractError("manifest_noncanonical")
+    return contract
+
+
 def validate_weekly_manifest(value: Mapping[str, object], expected: WeeklySourceContract) -> WeeklySourceContract:
     if not isinstance(expected, WeeklySourceContract):
         raise WeeklyContractError("manifest_expected_invalid")
     parsed = parse_weekly_manifest(value)
     if parsed != expected:
         raise WeeklyContractError("manifest_contract_mismatch")
+    if build_weekly_manifest(parsed) != dict(value):
+        raise WeeklyContractError("manifest_noncanonical")
     return parsed
 
 

tests/test_weekly_manifest.py

@@ -10,6 +10,7 @@
     MANIFEST_TYPE,
     build_weekly_manifest,
     parse_weekly_manifest,
+    parse_weekly_manifest_bytes,
     serialize_weekly_manifest,
     validate_weekly_manifest,
     write_weekly_manifest,
@@ -36,6 +37,19 @@ def test_weekly_manifest_is_deterministic_and_round_trips():
     encoded = serialize_weekly_manifest(contract)
     assert encoded == serialize_weekly_manifest(parse_weekly_manifest(json.loads(encoded)))
     assert parse_weekly_manifest(manifest) == contract
+    assert parse_weekly_manifest_bytes(encoded) == contract
+
+
+@pytest.mark.parametrize("wire", [
+    lambda encoded: b" " + encoded,
+    lambda encoded: encoded.replace(b'"contract":', b'"contract" :'),
+    lambda encoded: encoded.replace(b'"manifest_type":', b'"manifest_type":"x","manifest_type":'),
+])
+def test_manifest_wire_must_be_exact_canonical_bytes(wire):
+    contract = parse_weekly_contract(contract_payload())
+    encoded = serialize_weekly_manifest(contract)
+    with pytest.raises(WeeklyContractError):
+        parse_weekly_manifest_bytes(wire(encoded))
 
 
 @pytest.mark.parametrize("field,value", [
@@ -53,6 +67,14 @@ def test_manifest_contract_tamper_is_rejected(field, value):
         validate_weekly_manifest(manifest, contract)
 
 
+def test_mapping_with_alias_or_unknown_shape_fails_closed():
+    contract = parse_weekly_contract(contract_payload())
+    manifest = build_weekly_manifest(contract)
+    manifest["contract"]["generatedAt"] = manifest["contract"].pop("generated_at")
+    with pytest.raises(WeeklyContractError):
+        validate_weekly_manifest(manifest, contract)
+
+
 def test_manifest_feed_partial_and_shape_tamper_fail_closed():
     contract = parse_weekly_contract(contract_payload())
     manifest = build_weekly_manifest(contract)