From 12ff15e55b22fb022fb980021c7ef9db7aa09479 Mon Sep 17 00:00:00 2001
From: Jun-te Kim <juntekim@googlemail.com>
Date: Wed, 10 Jun 2026 15:21:00 +0000
Subject: [PATCH] =?UTF-8?q?Parse=2020.0.0=20conservatory=20building=20part?=
 =?UTF-8?q?s=20so=20all=201000=20certs=20map=20=F0=9F=9F=A9?=
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Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
---
 .../domain/tests/test_from_rdsap_schema.py    | 34 +++++++++++++++++++
 datatypes/epc/schema/rdsap_schema_20_0_0.py   | 30 +++++++++-------
 2 files changed, 52 insertions(+), 12 deletions(-)

diff --git a/datatypes/epc/domain/tests/test_from_rdsap_schema.py b/datatypes/epc/domain/tests/test_from_rdsap_schema.py
index f536cbb7..fb4cce54 100644
--- a/datatypes/epc/domain/tests/test_from_rdsap_schema.py
+++ b/datatypes/epc/domain/tests/test_from_rdsap_schema.py
@@ -1365,3 +1365,37 @@ class TestRdSap20_0_0ReducedFieldSynthesis:
         # Assert
         assert result.sap_heating.number_baths == expected_baths
         assert result.sap_heating.mixer_shower_count == expected_mixers
+
+    def test_conservatory_building_part_maps_without_missing_required_field(
+        self,
+    ) -> None:
+        # Arrange — ADR-0027: 17/1000 certs lodge a conservatory-shaped
+        # sap_building_part carrying only {double_glazed, floor_area,
+        # glazed_perimeter, room_height} — NOT the wall/roof/floor construction
+        # fields. The placeholder schema declared identifier (and the
+        # construction fields) required, so all 17 failed to parse. Following
+        # the 21.0.1 precedent, every SapBuildingPart field is Optional and the
+        # conservatory's effect is carried separately by conservatory_type, so
+        # the all-None part flows through harmlessly.
+        corpus = _load_20_0_0_corpus()
+        if not corpus:
+            pytest.skip("no RdSAP-Schema-20.0.0 corpus harvested")
+        cert = next(
+            (
+                c
+                for c in corpus
+                if any(
+                    "identifier" not in part
+                    for part in c.get("sap_building_parts", [])
+                )
+            ),
+            None,
+        )
+        if cert is None:
+            pytest.skip("no corpus cert with a conservatory building part")
+
+        # Act
+        result = EpcPropertyDataMapper.from_api_response(cert)
+
+        # Assert
+        assert isinstance(result, EpcPropertyData)
diff --git a/datatypes/epc/schema/rdsap_schema_20_0_0.py b/datatypes/epc/schema/rdsap_schema_20_0_0.py
index 2c959924..dbd5feef 100644
--- a/datatypes/epc/schema/rdsap_schema_20_0_0.py
+++ b/datatypes/epc/schema/rdsap_schema_20_0_0.py
@@ -128,18 +128,24 @@ class SapAlternativeWall:
 
 @dataclass
 class SapBuildingPart:
-    identifier: str
-    wall_dry_lined: str
-    floor_heat_loss: int
-    roof_construction: int
-    wall_construction: int
-    building_part_number: int
-    sap_floor_dimensions: List[SapFloorDimension]
-    wall_insulation_type: int
-    construction_age_band: str
-    party_wall_construction: Union[int, str]
-    wall_thickness_measured: str
-    roof_insulation_location: Union[int, str]
+    # ADR-0027: 17/1000 certs lodge a CONSERVATORY-shaped building part carrying
+    # only {double_glazed, floor_area, glazed_perimeter, room_height} — none of
+    # the wall/roof/floor construction fields below. Following the 21.0.1
+    # precedent every field is Optional, so a conservatory part parses to an
+    # all-None SapBuildingPart; its thermal effect is carried separately by the
+    # cert-level conservatory_type, so the empty part flows through harmlessly.
+    identifier: Optional[str] = None
+    wall_dry_lined: Optional[str] = None
+    floor_heat_loss: Optional[int] = None
+    roof_construction: Optional[int] = None
+    wall_construction: Optional[int] = None
+    building_part_number: Optional[int] = None
+    sap_floor_dimensions: Optional[List[SapFloorDimension]] = None
+    wall_insulation_type: Optional[int] = None
+    construction_age_band: Optional[str] = None
+    party_wall_construction: Optional[Union[int, str]] = None
+    wall_thickness_measured: Optional[str] = None
+    roof_insulation_location: Optional[Union[int, str]] = None
     # ADR-0027: absent on 254/1506 building parts (flat-roof / no-loft) → optional.
     roof_insulation_thickness: Optional[Union[str, int]] = None
     sap_room_in_roof: Optional[SapRoomInRoof] = None