awwx · May 4, 2024 11:19
diff --git a/mobserve.cljc b/mobserve.cljc
 ;; Newer version at https://gist.github.com/awwx/6d02e6ea702bdc499bcf847e9b9bb98f

 (ns mobserve
  (:require
   [missionary.core :as m]))

 ;; Encapsulate differences between Clojure and ClojureScript
 ;; on how IFn and IDeref are implemented.

 #?(:clj
   (deftype FlowIterator [transfer cancel]
     clojure.lang.IDeref
     (deref [_this]
       (transfer))

     clojure.lang.IFn
     (invoke [_this]
       (cancel)))

   :cljs
   (deftype FlowIterator [transfer cancel]
     IDeref
     (-deref [_this]
       (transfer))

     IFn
     (-invoke [_this]
       (cancel))))

 (defn println-reporter [description msg & args]
  ;; Lazy evaluation interacts badly with dynamic binding;
  ;; evaluate the pr-str before println changes the print mode.
  (let [pr-args (mapv pr-str args)]
    (apply println description msg pr-args)))

 (defn observe-task
  ([description task]
   (observe-task println-reporter description task))

  ([report description task]
   (fn [s f]
     (let [cancel! (task
                    (fn [v]
                      (report description :succeeded v)
                      (s v))
                    (fn [e]
                      (report description :failed e)
                      (f e)))]
       (report description :instantiated)
       (fn []
         (report description :canceled)
         (cancel!))))))

 (defn hook-call [thunk successful-call call-threw]
  (try
    (let [v (thunk)]
      ;; This isn't quite right: we catch errors thrown by
      ;; `successful-call`, not just `thunk`.
      (successful-call v)
      v)
    (catch #?(:clj Throwable, :cljs :default) e
      (call-threw e)
      (throw e))))

 (defn observe-flow
  ([description flow]
   (observe-flow println-reporter description flow))

  ([report description flow]
   (fn [notifier terminator]
     (let [child-iterator
           (flow
            (fn notify []
              (report description :notified)
              (notifier))
            (fn terminate []
              (report description :terminated)
              (terminator)))]
       (report description :instantiated)
       (FlowIterator.
        (fn transfer []
          (hook-call
           (fn [] @child-iterator)
           (fn [v]
             (report description :transferred-value v))
           (fn [e]
             (report description :transferred-error e))))
       (fn cancel []
         (report description :cancel-signaled)
         (child-iterator)))))))
	;; Newer version at https://gist.github.com/awwx/6d02e6ea702bdc499bcf847e9b9bb98f

	(ns mobserve
	(:require
	[missionary.core :as m]))

	;; Encapsulate differences between Clojure and ClojureScript
	;; on how IFn and IDeref are implemented.

	#?(:clj
	(deftype FlowIterator [transfer cancel]
	clojure.lang.IDeref
	(deref [_this]
	(transfer))

	clojure.lang.IFn
	(invoke [_this]
	(cancel)))

	:cljs
	(deftype FlowIterator [transfer cancel]
	IDeref
	(-deref [_this]
	(transfer))

	IFn
	(-invoke [_this]
	(cancel))))

	(defn println-reporter [description msg & args]
	;; Lazy evaluation interacts badly with dynamic binding;
	;; evaluate the pr-str before println changes the print mode.
	(let [pr-args (mapv pr-str args)]
	(apply println description msg pr-args)))

	(defn observe-task
	([description task]
	(observe-task println-reporter description task))

	([report description task]
	(fn [s f]
	(let [cancel! (task
	(fn [v]
	(report description :succeeded v)
	(s v))
	(fn [e]
	(report description :failed e)
	(f e)))]
	(report description :instantiated)
	(fn []
	(report description :canceled)
	(cancel!))))))

	(defn hook-call [thunk successful-call call-threw]
	(try
	(let [v (thunk)]
	;; This isn't quite right: we catch errors thrown by
	;; `successful-call`, not just `thunk`.
	(successful-call v)
	v)
	(catch #?(:clj Throwable, :cljs :default) e
	(call-threw e)
	(throw e))))

	(defn observe-flow
	([description flow]
	(observe-flow println-reporter description flow))

	([report description flow]
	(fn [notifier terminator]
	(let [child-iterator
	(flow
	(fn notify []
	(report description :notified)
	(notifier))
	(fn terminate []
	(report description :terminated)
	(terminator)))]
	(report description :instantiated)
	(FlowIterator.
	(fn transfer []
	(hook-call
	(fn [] @child-iterator)
	(fn [v]
	(report description :transferred-value v))
	(fn [e]
	(report description :transferred-error e))))
	(fn cancel []
	(report description :cancel-signaled)
	(child-iterator)))))))