[Bug]: allOf in a request body silently drops fields for x-www-form-urlencoded requests

Start at iter_all_of_schemas in openapi_core/validation/schemas/validators.py and reproduce the form-body example with OpenAPI.from_dict and MockRequest. Verify that the allOf fields are retained and cast as expected, with no silent loss; add a regression test covering the x-www-form-urlencoded request.

Actual Behavior

If a form request body (application/x-www-form-urlencoded) uses allOf, and one of the allOf parts has a field that isn't a string (a boolean, integer,
or object), that whole allOf part gets dropped. Every field in it disappears from the result, even the string ones.

There's no error. result.errors is empty, so it looks like the request succeeded. The fields just silently go missing. A log.warning("invalid allOf schema found") is printed.

In the example below, the result is {'name': 'widget'}. Both enabled (a boolean) and label (a string) are gone, because they're in the same allOf part as the boolean.

Expected Behavior

The result should be {'name': 'widget', 'enabled': True, 'label': 'hello'}.

If I write the same fields as one plain object instead of using allOf, it works correctly and enabled is cast to True:

"schema": {
    "type": "object",
    "properties": {
        "name": {"type": "string"},
        "enabled": {"type": "boolean"},
        "label": {"type": "string"},
    },
}
# -> {'name': 'widget', 'enabled': True, 'label': 'hello'}

allOf should give the same result. And valid data should never be dropped
without an error.

Steps to Reproduce

Run this (only openapi_core is needed):

from openapi_core import OpenAPI
from openapi_core.testing import MockRequest

spec = OpenAPI.from_dict({
    "openapi": "3.0.1",
    "info": {"title": "repro", "version": "1.0.0"},
    "paths": {"/items": {"post": {
        "requestBody": {"content": {"application/x-www-form-urlencoded": {"schema": {
            "allOf": [
                {"$ref": "#/components/schemas/Flags"},
                {"type": "object", "properties": {"name": {"type": "string"}}},
            ]
        }}}},
        "responses": {"200": {"description": "ok"}},
    }}},
    "components": {"schemas": {"Flags": {
        "type": "object",
        "properties": {
            "enabled": {"type": "boolean"},
            "label": {"type": "string"},
        },
    }}},
})

request = MockRequest(
    host_url="http://example.com", method="post", path="/items",
    data=b"name=widget&label=hello&enabled=true",
    content_type="application/x-www-form-urlencoded",
)
result = spec.unmarshal_request(request)
print(result.body)     # {'name': 'widget'}
print(result.errors)   # []

Output:

invalid allOf schema found
{'name': 'widget'}
[]

OpenAPI Core Version

0.23.1

OpenAPI Core Integration

none (openapi_core.testing.MockRequest); first seen with Django

Affected Area(s)

unmarshalling, schema

References

This looks related to the older "allOf is treated as type: any" reports (#147, #149), but here the effect is different: valid data is silently dropped,
instead of just a confusing error message. It only happens for form bodies, where values arrive as strings.

It seems to come from iter_all_of_schemas in openapi_core/validation/schemas/validators.py. Each allOf part is checked against the raw value and skipped if it doesn't match. For form bodies the values are still strings at that point, so a part with enabled: {type: boolean} fails against the string "true", gets skipped, and its fields are never read.

Anything else we need to know?

No response

Would you like to implement a fix?

Yes