Cannot add swagger ui to a flask blueprint

[SpoonMeiser]

A blueprint should, for most purposes be indistinguishable from an application, and I think it makes perfect sense to have, say, a flask blueprint for an API, and add a swagger UI to that.

However, the flask handler contains this check:

    import flask
    if isinstance(doc.app, flask.Flask):
        return handler

Which fails, because flask.Blueprint is not a subclass of flask.Flask.

Perhaps the test should be:

    import flask.scaffold import Scaffold
    if isinstance(doc.app, Scaffold):
        return handler

Or perhaps it's safer like this as scaffold doesn't appear to be a documented part of the API:

    import flask
    if isinstance(doc.app, (flask.Flask, flask.Blueprint)):
        return handler