Cannot reference YAML files, treated as JSONs

Environment:

• MacOSX
• Chrome, Firefox
• swagger-ui version: 3.22.1
• installation: dist
• OAS version: 3.0.2

Problem description:

I have a simple openapi file, which references other files using $ref. Both the main spec and the included files are in YAML format. However, it looks like the browser expects the included files to be formatted as JSONs only.

Main file:

openapi: 3.0.2
info:
  title: tile
  description: description
paths:
  /services:
    get:
      summary: summary
      description: description
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                $ref: schemas/payload.yaml

Included file, schemas/payload.yaml:

type: object
properties:
  property:
    type: string
    description: description

When the main file is explored, swagger UI displays an error "Could not render this component, see the console", and JavaScript console shows the following warning:

TypeError: Cannot read property 'toJS' of undefined
    at t.value (response.jsx:104)
    at t.render (root-injects.jsx:93)
    at s._renderValidatedComponentWithoutOwnerOrContext (ReactCompositeComponent.js:796)
    at s._renderValidatedComponent (ReactCompositeComponent.js:819)
    at s.performInitialMount (ReactCompositeComponent.js:359)
    at s.mountComponent (ReactCompositeComponent.js:255)
    at Object.mountComponent (ReactReconciler.js:43)
    at X.mountChildren (ReactMultiChild.js:234)
    at X._createInitialChildren (ReactDOMComponent.js:701)
    at X.mountComponent (ReactDOMComponent.js:520)

This is not specific to responses, same issue observed, for example, if I try to $ref a path. Note, however, if I change the referenced file from YAML to JSON, adding curled brackets, commas, and quotes, it's handled by swagger UI correctly.

All files are served from the same server, Content-Type is application/json. If I change my server code to return application/yaml (which hasn't been accepted as a standard mime type yet, but still), UI is broken with 406 errors, as it sends "Accept: application/json" only.

Start by reproducing the referenced YAML case in the dist installation and inspect the response.jsx stack-trace location in the browser console. Done means Swagger UI renders responses and paths that use YAML $ref files, including when the server serves them with an appropriate YAML content type.