The error I’m seeing is TypeError: task.call is not a function

probably https://github.com/leonoel/missionary/issues/54

ah, that looks like timeout now takes the task as first arg instead of second?

(which I guess makes sense if you think about tasks as maps and flows as seqs)

also instead of failing on timeout it succeeds with an optional value

Do you have an idea why this would never log :x

(defn- wait-until
  [doc-ref pred]
  (m/timeout
   (->> (m/observe (fn [emit!] (.onSnapshot doc-ref emit!))) ; get flow of updates to document
        (m/eduction (comp (map (fn [x] (js/console.log :x x) x))
                          (take 1)))
        (m/reduce #(do (js/console.log :wait-reduced %2) (reduced %2)))) ; return doc
   10000)) ; fail after 10s

it does log wait-reduced nil

reduce is wrong, if initial value is not provided the reducer must have zero arity

I’m not sure I understand, zero arity would mean no arguments? how would that work?

The docstring doesn’t indicate this btw.

I think it does

clojure.core/reduce does that too

e.g (reduce conj (range 10)) will call conj with no argument to get the seed

Ah, ok I think I’m getting there

it’ll call (reduced nil) if theres no initial value

A utility to return the first value of a flow and terminate after it could be nice maybe

Also interestingly the code above worked fine with b.20

I don't fully understand why. It may be due to https://github.com/leonoel/missionary/issues/13 however it looks like in clojurescript when a function is called for an undefined arity it's called for a superior arity with nil args instead of raising an exception