Remove early returns from validator

to increase readability

leasing/serializers/rent.py

@@ -21,6 +21,7 @@
     RentAdjustment,
     RentDueDate,
     RentIntendedUse,
+    ServiceUnit,
 )
 from leasing.models.rent import (
     EqualizedRent,
@@ -639,62 +640,39 @@ def full_validate_override_receivable_type(
         Raises: serializers.ValidationError
         """
         rent = Rent.objects.select_related("lease__service_unit").get(pk=rent_id)
-        use_rent_override_receivable_type: bool = (
+        rents_service_unit_uses_override: bool = (
             rent.lease.service_unit.use_rent_override_receivable_type
         )
         override_receivable_type: ReceivableType | None = rent_data.get(
             "override_receivable_type"
         )
-
-        if (not use_rent_override_receivable_type) and (not override_receivable_type):
-            # This service unit does not use the override receivabletype feature,
-            # and none was supplied -> all good.
-            # For example, service unit MaKe/Tontit.
-            return
-
-        if use_rent_override_receivable_type and override_receivable_type:
-            if rent_type_uses_override:
-                # Override receivabletype is required, was supplied, and rent
-                # type is correct -> all good.
-                # For example, service units AKV and KuVa.
-                return
-            else:
-                raise serializers.ValidationError(
-                    _(
-                        f'Override receivabletype "{override_receivable_type.name}" was unexpected. '
-                        f"This rent type does not generate automatic invoices. "
-                        "Please contact MVJ developers about this error."
-                    )
-                )
-
-        if use_rent_override_receivable_type and (not override_receivable_type):
-            if not rent_type_uses_override:
-                # This rent type does not utilize rent_override_receivable_type,
-                # even if the service unit generally uses it.
-                return
-            else:
-                raise serializers.ValidationError(
-                    _(
-                        f'Override receivabletype is required for service unit "{rent.lease.service_unit.name}", '
-                        f"and for this rent type."
-                    )
-                )
-
-        if (not use_rent_override_receivable_type) and override_receivable_type:
+        if override_receivable_type and (not rents_service_unit_uses_override):
             raise serializers.ValidationError(
                 _(
-                    f'Override receivabletype "{override_receivable_type.name}" was unexpected. '
+                    f'Override receivable type "{override_receivable_type.name}" was unexpected. '
                     f'Service unit "{rent.lease.service_unit.name}" does not use this feature. '
                     "Please contact MVJ developers about this error."
                 )
             )
-
-        raise serializers.ValidationError(
-            _(
-                "Unhandled case in override receivabletype validation. Rejecting just in case. "
-                "Please contact MVJ developers about this error."
+        if override_receivable_type and (not rent_type_uses_override):
+            raise serializers.ValidationError(
+                _(
+                    f'Override receivable type "{override_receivable_type.name}" was unexpected. '
+                    f"This rent type does not generate automatic invoices. "
+                    "Please contact MVJ developers about this error."
+                )
+            )
+        if (
+            rents_service_unit_uses_override
+            and rent_type_uses_override
+            and (not override_receivable_type)
+        ):
+            raise serializers.ValidationError(
+                _(
+                    "Override receivable type is required for this rent type in service unit "
+                    f'"{rent.lease.service_unit.name}".'
+                )
             )
-        )
 
     def minimal_validate_override_receivable_type(
         self,
@@ -725,25 +703,15 @@ def minimal_validate_override_receivable_type(
             # Without it, we cannot make further validations about its properties.
             return
 
-        service_unit = override_receivable_type.service_unit
-        receivabletypes_service_unit_uses_override = (
-            service_unit.use_rent_override_receivable_type
-        )
-
-        if receivabletypes_service_unit_uses_override and rent_type_uses_override:
-            # Service unit and rent types require an override receivabletype, and it was supplied
-            # --> all good.
-            return
-
-        if not receivabletypes_service_unit_uses_override:
+        service_unit: ServiceUnit = override_receivable_type.service_unit
+        if not service_unit.use_rent_override_receivable_type:
             raise serializers.ValidationError(
                 _(
                     f'Override receivabletype "{override_receivable_type.name}" was unexpected. '
                     f'Override receivabletype is not used by service unit "{service_unit.name}". '
                     "Please contact MVJ developers about this error."
                 )
             )
-
         if not rent_type_uses_override:
             raise serializers.ValidationError(
                 _(