Fix empty-band-list crash in get_rate_fixed_charge_at_dt when all bands are filtered by BOOLEAN applicabilitt

tariff_fetch/urdb/arcadia/fixedcharge.py

@@ -44,6 +44,7 @@ def get_fixed_charge_at_dt(scenario: Scenario, library: Library, dt: datetime) -
     master_tariff_id = scenario.master_tariff_id
     tariff = library.tariffs.get_tariff_at_date(master_tariff_id, dt.date())
     rates = ru.tariff_iter_rates_for_dt(tariff, scenario, library, dt)
+    rates = list(rates)
     return sum(get_rate_fixed_charge_at_dt(scenario, library, rate, dt) for rate in rates)
 
 
@@ -53,14 +54,14 @@ def get_rate_fixed_charge_at_dt(scenario: Scenario, library: Library, rate: Tari
     bands = ru.rate_filter_bands(rate, scenario, library)
     if rate["charge_type"] != "FIXED_PRICE":
         return 0
+    if not bands:
+        return 0
     if (variable_factor_key := rate.get("variable_factor_key")) is not None and not (
         rate["charge_period"] == "MONTHLY" and variable_factor_key == "billingPeriodProrationFactor"
     ):
         raise RateConversionError(rate, "Fixed charges cannot have variable factors")
     if rate.get("quantity_key") is not None:
         raise RateConversionError(rate, "Rates with quantity_key are not supported for fixed charge conversion")
-    if not bands:
-        return 0
     band_rate_units = {band["rate_unit"] for band in bands}
     if (transaction_type := rate["transaction_type"]) != "BUY":
         raise RateConversionError(

tests/test_arcadia_urdb_fixedcharge.py

@@ -3,21 +3,60 @@
 from tariff_fetch.arcadia.schema.tariff import TariffExtended
 from tariff_fetch.urdb.arcadia.exception import RateConversionError
 from tariff_fetch.urdb.arcadia.fixedcharge import build_fixed_charge
-from tariff_fetch.urdb.arcadia.library import Library, TariffLibrary, VariablePropertyLibrary
+from tariff_fetch.urdb.arcadia.library import Library, PropertyValue, TariffLibrary, VariablePropertyLibrary
 from tariff_fetch.urdb.arcadia.scenario import Scenario
 from tests.arcadia_urdb_fixtures import BAND, RATE, TARIFF
 
 
-def make_stub_library(tariffs: list[TariffExtended]) -> Library:
+def make_stub_library(tariffs: list[TariffExtended], properties: dict[str, PropertyValue] | None = None) -> Library:
     tariff_library = TariffLibrary(None, None, tariffs)
     variables_library = VariablePropertyLibrary(None, None, None)
-    return Library(None, None, None, tariff_library=tariff_library, variables_library=variables_library)
+    return Library(None, properties, None, tariff_library=tariff_library, variables_library=variables_library)
 
 
 def make_stub_scenario(tariff: TariffExtended) -> Scenario:
     return Scenario(tariff["master_tariff_id"], 2025, False)
 
 
+def test_build_fixed_charge_inapplicable_bands_does_not_fail():
+    tariff: TariffExtended = {
+        **TARIFF,
+        "rates": [
+            {
+                **RATE,
+                "charge_type": "FIXED_PRICE",
+                "applicability_key": "APPLICABLE",
+                "charge_period": "MONTHLY",
+                "rate_bands": [
+                    {
+                        **BAND,
+                        "applicability_value": "true",
+                        "rate_amount": 2.0,
+                    }
+                ],
+                "quantity_key": "some_key",
+            }
+        ],
+        "properties": [
+            {
+                "key_name": "APPLICABLE",
+                "display_name": "applicable",
+                "data_type": "BOOLEAN",
+                "operator": "=",
+                "keyspace": "tariff",
+                "family": "service",
+                "description": "applicability",
+                "property_types": "APPLICABILITY",
+                "is_default": False,
+            }
+        ],
+    }
+    scenario = make_stub_scenario(tariff)
+    library = make_stub_library([tariff], properties={"APPLICABLE": "false"})
+    result = build_fixed_charge(scenario, library)
+    assert result.get("fixedchargefirstmeter") == 0
+
+
 def test_build_fixed_charge_returns_zero_when_no_fixed_rates_apply():
     tariff: TariffExtended = {
         **TARIFF,