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{"@context":"https://schema.org","@type":"QAPage","mainEntity":{"@type":"Question","name":"How to deal with openapi_core.casting.schemas.exceptions.CastError: Failed to cast value to object error","text":"
Hi,
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I'm using openapi-core to validate responses against this OpenAPI schema:
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https://digital.nhs.uk/restapi/oas/573240
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The error I'm getting is this:
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    def _cast_proparties(self, value: Any, schema_only: bool = False) -> Any:\n        if not isinstance(value, dict):\n>           raise CastError(value, self.schema[\"type\"])\nE           openapi_core.casting.schemas.exceptions.CastError: Failed to cast value to object type: b'\\n    \\n        \\n        \\n        {\"entry\":[{\"fullUrl\":\"https://internal-dev.api.service.nhs.uk/validated-relationships/FHIR/R4/RelatedPerson/47CD795E\",\"resource\":{\"id\":\"47CD795E\",\"identifier\":[{\"system\":\"https://fhir.nhs.uk/Id/nhs-number\",\"value\":\"9730675929\"}],\"patient\":{\"identifier\":{\"system\":\"https://fhir.nhs.uk/Id/nhs-number\",\"value\":\"9730676399\"},\"type\":\"Patient\"},\"relationship\":[{\"coding\":[{\"code\":\"MTH\",\"display\":\"mother\",\"system\":\"http://terminology.hl7.org/CodeSystem/v3-RoleCode\"}]}],\"resourceType\":\"RelatedPerson\"},\"search\":{\"mode\":\"match\"}}],\"link\":[{\"relation\":\"self\",\"url\":\"https://internal-dev.api.service.nhs.uk/validated-relationships-service-api/FHIR/R4/RelatedPerson?identifier=9730675929&patient%3Aidentifier=9730676399\"}],\"timestamp\":\"2024-04-23T17:01:35+00:00\",\"total\":1,\"type\":\"searchset\",\"resourceType\":\"Bundle\"}\\n'\n\n../../../../../Library/Caches/pypoetry/virtualenvs/tests-puqZLLMN-py3.9/lib/python3.9/site-packages/openapi_core/casting/schemas/casters.py:114: CastError\n
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The call I am making that raises this error is:
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    openapi_response = RequestsOpenAPIResponse(api_response)\n    openapi_request = RequestsOpenAPIRequest(api_response.request)\n    openapi.validate_response(openapi_request, openapi_response)\n
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Where api_response is a requests.models.Response:
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(Pdb) type(api_response)\n<class 'requests.models.Response'>\n(Pdb) api_response.content\nb'\\n    \\n        \\n        \\n        {\"entry\":[{\"fullUrl\":\"https://internal-dev.api.service.nhs.uk/validated-relationships/FHIR/R4/RelatedPerson/47CD795E\",\"resource\":{\"id\":\"47CD795E\",\"identifier\":[{\"system\":\"https://fhir.nhs.uk/Id/nhs-number\",\"value\":\"9730675929\"}],\"patient\":{\"identifier\":{\"system\":\"https://fhir.nhs.uk/Id/nhs-number\",\"value\":\"9730676399\"},\"type\":\"Patient\"},\"relationship\":[{\"coding\":[{\"code\":\"MTH\",\"display\":\"mother\",\"system\":\"http://terminology.hl7.org/CodeSystem/v3-RoleCode\"}]}],\"resourceType\":\"RelatedPerson\"},\"search\":{\"mode\":\"match\"}}],\"link\":[{\"relation\":\"self\",\"url\":\"https://internal-dev.api.service.nhs.uk/validated-relationships-service-api/FHIR/R4/RelatedPerson?identifier=9730675929&patient%3Aidentifier=9730676399\"}],\"timestamp\":\"2024-04-24T10:05:26+00:00\",\"total\":1,\"type\":\"searchset\",\"resourceType\":\"Bundle\"}\\n'\n
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So it looks like openapi-core is expecting a dict but is getting bytes:
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\n  
\n    
\n      openapi-core/openapi_core/casting/schemas/casters.py\n    
\n    
\n        Lines 113 to 114\n      in\n      99af2d3\n    
\n  
\n  
\n    \n\n        \n          \n          \n        \n\n        \n          \n          \n        \n    
 if not isinstance(value, dict): 
     raise CastError(value, self.schema[\"type\"]) 
\n  
\n
\n
\n
(Pdb) openapi_response.data\nb'\\n    \\n        \\n        \\n        {\"entry\":[{\"fullUrl\":\"https://internal-dev.api.service.nhs.uk/validated-relationships/FHIR/R4/RelatedPerson/47CD795E\",\"resource\":{\"id\":\"47CD795E\",\"identifier\":[{\"system\":\"https://fhir.nhs.uk/Id/nhs-number\",\"value\":\"9730675929\"}],\"patient\":{\"identifier\":{\"system\":\"https://fhir.nhs.uk/Id/nhs-number\",\"value\":\"9730676399\"},\"type\":\"Patient\"},\"relationship\":[{\"coding\":[{\"code\":\"MTH\",\"display\":\"mother\",\"system\":\"http://terminology.hl7.org/CodeSystem/v3-RoleCode\"}]}],\"resourceType\":\"RelatedPerson\"},\"search\":{\"mode\":\"match\"}}],\"link\":[{\"relation\":\"self\",\"url\":\"https://internal-dev.api.service.nhs.uk/validated-relationships-service-api/FHIR/R4/RelatedPerson?identifier=9730675929&patient%3Aidentifier=9730676399\"}],\"timestamp\":\"2024-04-24T10:15:31+00:00\",\"total\":1,\"type\":\"searchset\",\"resourceType\":\"Bundle\"}\\n'\n(Pdb) type(openapi_response.data)\n<class 'bytes'>\n
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I have worked round this by subclassing RequestsOpenAPIResponse so the data attribute returns a dict which works for me but I'd like to understand why I'm seeing this issue in the first place and what, if anything, I am doing wrong.
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Thanks
","upvoteCount":2,"answerCount":1,"acceptedAnswer":{"@type":"Answer","text":"
Exactly that; you can use the same function as standard one
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from openapi_core.deserializing.media_types.util import json_loads
","upvoteCount":0,"url":"https://github.com/python-openapi/openapi-core/discussions/838#discussioncomment-9220988"}}}