fix(generator): nullable inline object schema crashes on nil value (DataDog#3976)

When a BDD scenario sends null for a nullable field whose schema is an
inline object (no \$ref), reference_to_value raised NotImplementedError
because it tried to look up a NewNullableXxx function that doesn't exist
for anonymous types. Since nil doesn't need wrapping, return it directly.

Co-authored-by: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

Author: MintsInc

.generator/src/generator/formatter.py

@@ -268,6 +268,8 @@ def reference_to_value(schema, value, print_nullable=True, **kwargs):
     if nullable:
         function_name = schema_name(schema)
         if function_name is None:
+            if value == "nil":
+                return "nil"
             raise NotImplementedError(f"nullable {schema} is not supported")
         return formatter.format(prefix=prefix, function_name=function_name, value=value)
     return f"&{value}"

.generator/tests/test_formatter.py

@@ -83,3 +83,15 @@ def test_named_typed_additional_properties_as_array_item_generates_typed_map_sli
         result = format_data_with_schema([{"k": "v"}], array_schema)
         assert "StringMapItem" not in result
         assert "map[string]string" in result
+
+
+class TestNullableInlineObjectWithNullValue:
+    """Nullable inline (anonymous) object schemas must return 'nil' when data is None."""
+
+    def test_nullable_inline_object_returns_nil(self):
+        schema = {"type": "object", "nullable": True}
+        assert format_data_with_schema(None, schema) == "nil"
+
+    def test_nullable_inline_object_with_additional_properties_returns_nil(self):
+        schema = {"type": "object", "nullable": True, "additionalProperties": {}}
+        assert format_data_with_schema(None, schema) == "nil"