OpenAPIParser is resolving the wrong schema for an operation

See the following repo for a minimal reproduction of this issue:

• https://github.com/simondean/swagger-request-validator-filename-issue
• https://github.com/simondean/swagger-request-validator-filename-issue/blob/main/src/test/java/IssueDemoTest.java
• https://github.com/simondean/swagger-request-validator-filename-issue/blob/main/example-openapi.yaml

Here's an example OpenAPI spec that demonstrates the issue:

https://github.com/simondean/swagger-request-validator-filename-issue/blob/main/example-openapi.yaml

openapi: 3.0.1
info:
  title: Example OpenAPI spec
  version: 0.0.1
paths:
  '/example':
    post:
      requestBody:
        content:
          application/json:
            schema:
              $ref: '#/components/schemas/ExamplePost'
      responses:
        204:
          description: No content
components:
  schemas:
    # Renaming this key from `Example` to `ExampleGet` stops the issue from occurring
    # Removing this key stops the issue from occurring
    Example:
      $ref: example.get.yaml
    ExamplePost:
      $ref: example.post.yaml

The comments in the code snippet show how the issue only happens when the unused schema is called Example. Rename it to ExampleGet or delete it, and the issue stops. The word Example is unimportant, other than it seems to need to be similar to the other schema that is used. Both schemes could be renamed to Anything and AnythingPost and you would still get the issue

Expected Behaviour

The following assertion should pass:

        assertEquals("POST Example", api.getPaths()
                .get("/example")
                .getPost()
                .getRequestBody()
                .getContent()
                .get("application/json")
                .getSchema()
                .getTitle());

Actual Behaviour

Swagger Parser loads the wrong request body schema for the POST operation. It's request body description is set to GET Example when it should be POST Example:

expected: <POST Example> but was: <GET Example>

Start with the linked IssueDemoTest.java and example-openapi.yaml to reproduce the incorrect POST schema resolution. Trace how OpenAPIParser resolves the referenced schemas, then confirm the assertion expects "POST Example" rather than "GET Example" when the unused Example schema is present.