Properties that are a reference are not expandable

[niknetniko]

When a property of a model is a reference to another model, the property is not expandable.

---

Example spec:

openapi: "3.0.0"
info:
  version: 1.0.0
  title: Example API
  description: Hello
paths:
  /examples/{id}:
    parameters:
      - in: path
        name: id
        schema:
          type: string
        description: The ID of the customer.
        required: true
    put:
      tags: [Examples]
      summary: Get an Example
      requestBody:
        content:
            application/json:
              schema:
                $ref: '#/components/schemas/Example'
      responses:
        '200':
          description: OK
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Example'
            application/xml:
              schema:
                $ref: '#/components/schemas/Example'

components:
  schemas:
    Metadata:
      description: About the entity.
      readOnly: true
      properties:
        createdBy:
          type: string
          description: Who made it.
        createdAt:
          type: string
          description: When they made it.
          format: date-time
    Example:
      description: An example model.
      required: [test, meta]
      properties:
        test:
          type: string
          description: A test field.
        meta:
          $ref: '#/components/schemas/Metadata'
tags:
- name: Examples
  description: |
    A small example demonstrating the issue.

See the result here: https://rebilly.github.io/ReDoc/?url=https://gist.githubusercontent.com/niknetniko/ebdd032f6e4e132c0864b32181bfaef1/raw/61fe049675904795b9b45adaacffa7acbaa3800a/sample.yaml#tag/Examples

As you can, the meta field of the Example model is not expandable in the documentation.

---

I think I have found where the bug is:
https://github.com/Rebilly/ReDoc/blob/597688e7208159864c0d5964237df6fb3445e2b7/src/services/models/Schema.ts#L96
At this line, the schema's type is used or type detection happens. However, for references, the type of the schema is undefined. This is no problem; the type detections correctly determines that it is in fact an object. The problem lies later: multiple functions rely on the schema's type, which is undefined.
I believe this could be fixed by:

1. Finding out why (if this is a problem, not sure) a property with referenced model has an undefined type
2. Set the type of the schema to the one returned by detectType (I'm not sure if this breaks things)

[RomanHotsiy]

Thanks for the detailed issue report and for digging into source code 🙌.
I will fix this.

For now, you can easily workaround the issue:

Finding out why (if this is a problem, not sure) a property with referenced model has an undefined type

Just add type: object to the referenced model:

Metadata:
  type: object # <--- here
  description: About the entity.
  readOnly: true
  # ...

[niknetniko]

Thanks for the quick fix and the workaround 👍