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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Failure to correctly validate required in allOf","articleBody":"Having one spec with optional properties and creating a derived spec using `allOf` that makes a property required fails. This should be supported according to json schema itself (e.g. [here](https://github.com/OAI/OpenAPI-Specification/issues/1870#issuecomment-478653692))\r\n\r\nTo reproduce (with 0.1.5):\r\n\r\n```python\r\nfrom openapi_schema_validator import validate\r\n\r\n\r\nschema = {\r\n    \"allOf\": [\r\n        {\"type\": \"object\", \"properties\": {\"some_prop\": {\"type\": \"string\"}}},\r\n        {\"type\": \"object\", \"required\": [\"some_prop\"]},\r\n    ]\r\n}\r\n\r\nvalidate({\"another_prop\": \"bla\"}, schema)\r\n```\r\n\r\nExpected behaviour: an error that the required property `some_prop` is missing. The code actually correctly figures that out, but when it tries to check whether it is ok to have that property missing because it is e.g. a `readOnly` missing in a write operation a \"runtime\" error is produced instead of a validation exception:\r\n\r\n```python\r\n~/venvs/py39/lib/python3.9/site-packages/openapi_schema_validator/_validators.py in required(validator, required, instance, schema)\r\n     41     for property in required:\r\n     42         if property not in instance:\r\n---> 43             prop_schema = schema['properties'][property]\r\n     44             read_only = prop_schema.get('readOnly', False)\r\n     45             write_only = prop_schema.get('writeOnly', False)\r\n\r\nKeyError: 'properties'\r\n```\r\n\r\nThe problem is that here `schema` is only the second schema with the `required` - but the property can come from any schema in the `allOf`.","author":{"url":"https://github.com/sebastianmika","@type":"Person","name":"sebastianmika"},"datePublished":"2021-06-24T16:39:06Z","url":"https://github.com/python-openapi/openapi-schema-validator/issues/15"}