Can not get eager-pre-hook to run?

[lkrubner]

I have an odd problem. I have hooked to vars in other namespaces before, but now I seem to be not matching, perhaps because of my use of Slingshot.

I have namespace which starts as:

(ns loupi.persistence-queue
(:require
 [loupi.persistence :as persistence]
 [slingshot.slingshot :as slingshot]
 [clojure.pprint :as pp]
 [lamina.core :as lamina]))

 (defn persist-this-item [context-wrapper-for-database-call]
   {:pre [(map? context-wrapper-for-database-call)]}
   (lamina/enqueue persistence-channel
              (fn []
                (pp/pprint context-wrapper-for-database-call)
                (persistence/make-consistent context-wrapper-for-database-call)
                )))

And then I have another namespace where I want to add an eager pre-hook. I tried linking to the other var in these ways:

 (dire/with-eager-pre-hook! #'loupi.persistence-queue/persist-this-item
   "An optional docstring."
   (fn [a b] (println "Logging something before preconditions are evaluated.")))

and I also tried:

 (:require
      [loupi.persistence-queue :as pq]

 (dire/with-eager-pre-hook! #'pq/persist-this-item
   "An optional docstring."
   (fn [a b] (println "Logging something before preconditions are evaluated.")))

or just:

 (:use 
 [loupi.persistence-queue]) 

 (dire/with-eager-pre-hook! #'persist-this-item
   "An optional docstring."
   (fn [a b] (println "Logging something before preconditions are evaluated.")))

None of these seem to work.

This line runs and prints to stdout so I can see it in the terminal:

                (pp/pprint context-wrapper-for-database-call)

but I can not get the pre-hook to work. Any suggestions?

If I look at RobertHooke:

https://github.com/technomancy/robert-hooke/

They offer this example:

(add-hook #'some.ns/target-var #'hook-function)

And I feel like what I'm doing is similar, so I am unsure what I am doing wrong.

[lkrubner]

I guess this would happen if there had already been an exception on that thread, which had gone uncaught?

[MichaelDrogalis]

That's definitely plausible. I don't see anything wrong with your usage of the library. Does it work when used within the same namespace?

[lkrubner]

Strangely, if I do this:

   (ns loupi.persistence-queue
   (:require
    [loupi.persistence :as persistence]
    [slingshot.slingshot :as slingshot]
    [lamina.core :as lamina]
    [dire.core :as dr]))

 (def ^:private persistence-channel (lamina/channel))

 (defn persist-this-item [context-wrapper-for-database-call]
   (lamina/enqueue persistence-channel
                   (fn []
                     (persistence/make-consistent context-wrapper-for-database-call))))

 (dr/with-eager-pre-hook! #'persist-this-item
   "An optional docstring."
   (fn [a] (println "Logging something before preconditions are evaluated." )
     (println (str a))))

Then the "Logging something before preconditions are evaluated." shows up in my terminal. But if move the pre-hook to its own namespace:

(ns loupi.supervisor
  (:require
   [loupi.perpetual :as perpetual]
   [loupi.startup :as startup]
   [loupi.server :as server]
   [loupi.dates :as dt]
   [clojure.string :as st]
   [clj-stacktrace.core :as stack]
   [dire.core :as dire]
   [taoensso.timbre :as timbre]))

(dire/with-eager-pre-hook! #'loupi.persistence-queue/persist-this-item
  "An optional docstring."
  (fn [a b] (println "Logging something before preconditions are evaluated.")))

Then this does not appear in my terminal output: "Logging something before preconditions are evaluated.")

And it makes no difference if I use :use to include the namespace:

(ns loupi.supervisor
  (:require
   [loupi.perpetual :as perpetual]
   [loupi.startup :as startup]
   [loupi.server :as server]
   [loupi.dates :as dt]
   [clojure.string :as st]
   [clj-stacktrace.core :as stack]
   [dire.core :as dire]
   [taoensso.timbre :as timbre]
   (:use
    [loupi.persistence-queue])))

(dire/with-eager-pre-hook! #'loupi.persistence-queue/persist-this-item
  "An optional docstring."
  (fn [a b] (println "Logging something before preconditions are evaluated.")))

[MichaelDrogalis]

That's really weird. Are you sure the namespace containing the hooks is getting required before the function call?

[lkrubner]

Damn, that was obvious. I'd changed the order of things being required, and I'd left out a crucial one.

[MichaelDrogalis]

No problem, happens all the time! Closing unless anything else arises.