Refuse to cast str or bytes to array

openapi_core/casting/schemas/casters.py

@@ -54,6 +54,10 @@ def items_caster(self) -> BaseSchemaCaster:
         return self.casters_factory.create(self.schema / "items")
 
     def cast(self, value: Any) -> List[Any]:
+        # str and bytes are not arrays according to the OpenAPI spec
+        if isinstance(value, (str, bytes)):
+            raise CastError(value, self.schema["type"])
+
         try:
             return list(map(self.items_caster, value))
         except (ValueError, TypeError):

openapi_core/casting/schemas/exceptions.py

@@ -1,4 +1,5 @@
 from dataclasses import dataclass
+from typing import Any
 
 from openapi_core.exceptions import OpenAPIError
 
@@ -7,7 +8,7 @@
 class CastError(OpenAPIError):
     """Schema cast operation error"""
 
-    value: str
+    value: Any
     type: str
 
     def __str__(self) -> str:

tests/unit/casting/test_schema_casters.py

@@ -26,15 +26,17 @@ def test_array_invalid_type(self, caster_factory):
         with pytest.raises(CastError):
             caster_factory(schema)(value)
 
-    def test_array_invalid_value(self, caster_factory):
+    @pytest.mark.parametrize("value", [3.14, "foo", b"foo"])
+    def test_array_invalid_value(self, value, caster_factory):
         spec = {
             "type": "array",
             "items": {
-                "type": "number",
+                "oneOf": [{"type": "number"}, {"type": "string"}],
             },
         }
         schema = Spec.from_dict(spec)
-        value = 3.14
 
-        with pytest.raises(CastError):
+        with pytest.raises(
+            CastError, match=f"Failed to cast value to array type: {value}"
+        ):
             caster_factory(schema)(value)