core-async 2022-08-03 | Slack Archive

Think I’ve found a bug in core.async tests, the following test for mult working seems purely coincidental:

;; ASYNC-127
    (let [ch (to-chan! [1 2 3])
          m (mult ch)
          t-1 (chan)
          t-2 (chan)
          t-3 (chan)]
      (tap m t-1)
      (tap m t-2)
      (tap m t-3)
      (close! t-3)
      (is (= 1 (<!! t-1)))
      (is (= nil (a/poll! t-1))) ;; t-2 hasn't taken yet
      (is (= 1 (<!! t-2)))
      (is (= 2 (<!! t-1))) ;; now available
      (is (= nil (a/poll! t-1)))))

The docstring of core.async/mult states that: Items received when there are no taps get dropped. Following this statement, the 3 items put by to-chan! should be dropped, as when the mult is created, it would start consuming them without taps yet on the http://mult.My suspicion is that it passes because the go’s created inside mult and to-chan! might be slow enough to create so that the taps get executed before the mult starts consuming. Does this make sense? Am I missing something?

bortexz17:08:07

Logged in https://ask.clojure.org/index.php/12100/core-async-mult-test-is-passing-accidentally

ghadi17:08:19

#Also sent to the channel

answered over there @bertofer

👍 1

Alex Miller (Clojure team)16:08:53

possibly. I don't have time to look at it right now, but if you want to put it on https://ask.clojure.org, I will look at it eventually

👍 1

ghadi17:08:19

replied to a thread:Think I’ve found a bug in core.async tests, the following test for `mult` working seems purely coincidental: ;; ASYNC-127 (let [ch (to-chan! [1 2 3]) m (mult ch) t-1 (chan) t-2 (chan) t-3 (chan)] (tap m t-1) (tap m t-2) (tap m t-3) (close! t-3) (is (= 1 (<!! t-1))) (is (= nil (a/poll! t-1))) ;; t-2 hasn't taken yet (is (= 1 (<!! t-2))) (is (= 2 (<!! t-1))) ;; now available (is (= nil (a/poll! t-1))))) The docstring of core.async/mult states that: `Items received when there are no taps get dropped.` Following this statement, the 3 items put by to-chan! should be dropped, as when the mult is created, it would start consuming them without taps yet on the http://mult.My suspicion is that it passes because the go’s created inside `mult` and `to-chan!` might be slow enough to create so that the taps get executed before the mult starts consuming. Does this make sense? Am I missing something?

answered over there @bertofer

👍 1

2022-08-03

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