Allow zero-euro line item amounts

src/validator.py

@@ -5,6 +5,7 @@ import time
 from typing import Any
 
 from pydantic import ValidationError
+
 from src.models import (
     ErrorDetail,
     ValidateRequest,
@@ -78,10 +79,10 @@ def validate_pflichtfelder(xml_data: XmlData) -> list[ErrorDetail]:
             if item.quantity == 0:
                 add_error(f"{field_prefix}.quantity", "critical")
 
-            if item.unit_price == 0:
+            if item.unit_price is None:
                 add_error(f"{field_prefix}.unit_price", "critical")
 
-            if item.line_total == 0:
+            if item.line_total is None:
                 add_error(f"{field_prefix}.line_total", "critical")
 
             if item.vat_rate is None:
@@ -94,7 +95,7 @@ def validate_betraege(xml_data: XmlData) -> list[ErrorDetail]:
     """Check amount calculations are correct."""
     errors = []
 
-    def add_mismatch(field: str, expected: float, actual: float) -> None:
+    def add_mismatch(field: str, expected: float, actual: float | None) -> None:
         errors.append(
             ErrorDetail(
                 check="betraege",
@@ -107,16 +108,24 @@ def validate_betraege(xml_data: XmlData) -> list[ErrorDetail]:
 
     # Check line_total = quantity × unit_price
     for idx, item in enumerate(xml_data.line_items):
-        expected_line_total = item.quantity * item.unit_price
-        if not amounts_match(item.line_total, expected_line_total):
+        unit_price = item.unit_price
+        line_total = item.line_total
+        if unit_price is None or line_total is None:
+            continue
+
+        expected_line_total = item.quantity * unit_price
+        if not amounts_match(line_total, expected_line_total):
             add_mismatch(
                 f"line_items[{idx}].line_total",
                 expected_line_total,
-                item.line_total,
+                line_total,
             )
 
     # Check totals.net = sum(line_items.line_total)
-    line_total_sum = sum(item.line_total for item in xml_data.line_items)
+    line_total_sum = 0.0
+    for item in xml_data.line_items:
+        if item.line_total is not None:
+            line_total_sum += item.line_total
     if not amounts_match(xml_data.totals.net, line_total_sum):
         add_mismatch("totals.net", line_total_sum, xml_data.totals.net)
 
@@ -280,12 +289,14 @@ def validate_invoice(request: ValidateRequest) -> ValidationResult:
         xml_data = XmlData(**request.xml_data)
     except ValidationError as e:
         # Convert Pydantic validation errors to ValidationResult
-        validation_errors = []
+        validation_errors: list[ErrorDetail] = []
         for error in e.errors():
+            loc = error["loc"]
+            field = str(loc[0]) if loc else None
             validation_errors.append(
                 ErrorDetail(
                     check="schema_validation",
-                    field=error["loc"][0] if error["loc"] else None,
+                    field=field,
                     error_code=error["type"],
                     message=error["msg"],
                     severity="critical",