Handler and transient dependency middleware

[zalky]

I have a component that has its own middleware:

(defrecord SenteHandler [respond-to middleware]
  component/Lifecycle
  (start [component]
    (assoc component :handler
      (if middleware
        ((apply comp (reverse middleware)) respond-to)
        respond-to)))

  (stop [component]
    (dissoc component :handler)))

I am also using the system.component.handler/Handler component. My SenteHandler is a transient dependency of the system.components.handler/Handler:

{...
 :sente             [:sente-handler]
 :private-endpoints [:sente]
 :handler           [:public-endpoints
                     :private-endpoints
                     :middleware]}

When :middleware in SenteHandler is nil, Handler is throwing a NullPointerException on L37. If I change :middleware key in SenteHandler to anything else, such as :mw, Handler does not throw an exception. Handler seems to be searching for middleware in transient dependencies by checking for the :middleware key.

While this is fairly easy to work around, would it make things more robust to check the type of the component instead or checking for keywords that are not namespaced? Something like (instance? Middleware component)? I've thrown together a simple PR and it seems to work.

[danielsz]

Yes, that sounds like a good idea. Thank for the PR.
I'll take a closer look as soon as possible.