Pulp

The issue happens with fields with choices that are nullable

metadata_checksum_type = models.CharField(null=True, choices=CHECKSUM_CHOICES, max_length=10)
package_checksum_type = models.CharField(null=True, choices=CHECKSUM_CHOICES, max_length=10)

drf_spectacular uses oneOf to distinguish the options null/choice

"metadata_checksum_type": {
    "nullable": true,
    "description": "The checksum type for metadata.",
    "oneOf": [
        {
            "$ref": "#/components/schemas/MetadataChecksumTypeEnum"
        },
        {
            "$ref": "#/components/schemas/NullEnum"
        }
    ]
},
"package_checksum_type": {
    "nullable": true,
    "description": "The checksum type for packages.",
    "oneOf": [
        {
            "$ref": "#/components/schemas/PackageChecksumTypeEnum"
        },
        {
        "$ref": "#/components/schemas/NullEnum"
        }
    ]
},

pulp-openapi-generator creates these models:

MetadataChecksumTypeEnum, PackageChecksumTypeEnum and NullEnum

The issue happens when declaring the types:

openapi_types = {
    'pulp_labels': 'object',
    'name': 'str',
    'description': 'str',
    'retain_repo_versions': 'int',
    'remote': 'str',
    'autopublish': 'bool',
    'metadata_signing_service': 'str',
    'retain_package_versions': 'int',
    'metadata_checksum_type': 'OneOfMetadataChecksumTypeEnumNullEnum',
    'package_checksum_type': 'OneOfPackageChecksumTypeEnumNullEnum',
    'gpgcheck': 'int',
    'repo_gpgcheck': 'int',
    'sqlite_metadata': 'bool'
}

what would be type PackageChecksumTypeEnum or NullEnum is declared as OneOfPackageChecksumTypeEnumNullEnum

PR: https://github.com/pulp/pulpcore/pull/1561