Bug in definition of callbacks

[ThomasR]

I'm talking about the callbacks field callbacks :== Map[string, Callback Object | Reference Object]

The key value used to identify the callback object is an expression, evaluated at runtime, that identifies a URL to use for the callback operation.

both defined in
https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#operationObject
and
https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#callbackObject

This means that this is a valid callbacks map:

callbacks:
  "$request.query.queryUrl": # key value used to identify the callback object
    <CallbackObject>
  "$url":  # key value used to identify the callback object
    <CallbackObject>

Now, by definition of a Callback Object:

The key that identifies the Path Item Object is a runtime expression that can be evaluated in the context of a runtime HTTP request/response to identify the URL to be used for the callback request.

https://github.com/OAI/OpenAPI-Specification/blob/master/versions/3.0.2.md#key-expression

so we end up with some mess like this:

callbacks:
  "$request.query.queryUrl": # key value used to identify the callback object
    "$request.query.queryUrl": # key that identifies the Path Item Object
      <PathItemObject>
    "$url": # key that identifies the Path Item Object
      <PathItemObject>
  "$url":  # key value used to identify the callback object
    "$request.query.queryUrl":  # key that identifies the Path Item Object
      <PathItemObject>
    "$url": # key that identifies the Path Item Object
      <PathItemObject>

This makes no sense to me and I'm assuming it's a bug. Reading through #1141, I think that the intention was to make this example valid

callbacks:
  "foo":
    <CallbackObject>
  "bar":
    <CallbackObject>

but it's not, because the literals "foo", "bar" are not runtime expressions.

[ahl]

You might check out these docs:
https://swagger.io/docs/specification/callbacks/

[MikeRalphson]

Think this can be closed as #1899 was merged.