feat: handle default values for namedtuple params in decoder

Author: lemorage

python/cocoindex/convert.py

@@ -110,10 +110,12 @@ def _make_engine_struct_value_decoder(
     if is_dataclass:
         parameters = inspect.signature(dst_struct_type).parameters
     elif is_namedtuple:
+        defaults = getattr(dst_struct_type, '_field_defaults', {})
         parameters = {
             name: inspect.Parameter(
                 name=name,
                 kind=inspect.Parameter.POSITIONAL_OR_KEYWORD,
+                default=defaults.get(name, inspect.Parameter.empty),
                 annotation=dst_struct_type.__annotations__.get(name, inspect.Parameter.empty)
             )
             for name in dst_struct_type._fields
@@ -128,7 +130,7 @@ def make_closure_for_value(name: str, param: inspect.Parameter) -> Callable[[lis
             field_decoder = make_engine_value_decoder(
                 field_path, src_fields[src_idx]['type'], param.annotation)
             field_path.pop()
-            return lambda values: field_decoder(values[src_idx])
+            return lambda values: field_decoder(values[src_idx]) if len(values) > src_idx else param.default
 
         default_value = param.default
         if default_value is inspect.Parameter.empty:

python/cocoindex/tests/test_convert.py

@@ -146,6 +146,12 @@ def test_make_engine_value_decoder_basic_types():
         # Extra field in engine value for Customer (should ignore)
         (Customer, ["Alice", ["O1", "item1", 10.0, "default_extra"], [["vip"]], "extra"], Customer("Alice", Order("O1", "item1", 10.0, "default_extra"), [Tag("vip")])),
         (CustomerNamedTuple, ["Alice", ["O1", "item1", 10.0, "default_extra"], [["vip"]], "extra"], CustomerNamedTuple("Alice", OrderNamedTuple("O1", "item1", 10.0, "default_extra"), [Tag("vip")])),
+        # Missing optional field with default
+        (Order, ["O123", "mixed nuts", 25.0], Order("O123", "mixed nuts", 25.0, "default_extra")),
+        (OrderNamedTuple, ["O123", "mixed nuts", 25.0], OrderNamedTuple("O123", "mixed nuts", 25.0, "default_extra")),
+        # Partial optional fields
+        (Customer, ["Alice", ["O1", "item1", 10.0]], Customer("Alice", Order("O1", "item1", 10.0, "default_extra"), None)),
+        (CustomerNamedTuple, ["Alice", ["O1", "item1", 10.0]], CustomerNamedTuple("Alice", OrderNamedTuple("O1", "item1", 10.0, "default_extra"), None)),
     ]
 )
 def test_struct_decoder_cases(data_type, engine_val, expected):