Discriminator property is not validated

Accordingly with the OpenAPI spec when you define a discriminator the name should be in the schema and must be required:

discriminator | string | Adds support for polymorphism. The discriminator is the schema property name that is used to differentiate between other schema that inherit this schema. The property name used MUST be defined at this schema and it MUST be in the required property list. When used, the value MUST be the name of this schema or any schema that inherits it.

Should this trigger a parse error?

Acceptance criteria

• Parser should fail (at least warn) if the above criteria is not fulfilled

The issue does not name a source file or test. Start by locating the parser's discriminator validation entry point and review the OpenAPI requirements quoted here; done means an invalid discriminator causes at least a warning or parse failure, with coverage for a missing schema property and a missing required entry.