That would be easier to understand, but how did you know?

The source code is (. clojure.lang.RT (keys map))…

https://github.com/clojure/clojure/blob/master/src/jvm/clojure/lang/RT.java#L620

My tests indicate me that it doesn't, but I find it very surprising.

If you have a short sequence of expressions one can type into a REPL to reproduce that, it would help.

Also, are you trying to print out (meta <some-value>) inside of your tap function, and it is returning nil? Or what other evidence are you seeing to indicate that you are not getting metadata on these values?

@U0CMVHBL2 yep:

(do
  (defn tap-internal [value]
    (println (meta value)))

  (add-tap tap-internal)
  (tap> ^{:test "meta"} (range 10)))

(prints nil)

Maybe not a good test, because

user=> (meta ^{:foo 5} (range 10))
nil

Try instead (tap> (with-meta (range 10) {:test "meta"}))

Hmm, can you explain me the reason for this? I thought that was how the ^ reader macro supposed to work

That macro does put metadata on the list (range 10), but not on the result of evaluating the expression (range 10), which is what is being passed as an argument.

oh I see, that makes sense, thank you.

I am getting results I do not know how to explain off the top of my head when using quoted literal lists, but with vectors these examples might clarify things:

user=> (def v1 ^{:foo "x"} [0 1 2 3 4])
#'user/v1
user=> v1
[0 1 2 3 4]
user=> (meta v1)
{:foo "x"}
user=> (def v2 ^{:foo "x"} (vec (range 5)))
#'user/v2
user=> v2
[0 1 2 3 4]
user=> (meta v2)
nil

The expression whose value is bound to v1 is a literal vector in the source code. The Clojure reader attaches metadata to this literal vector at read time, and when evaluated a literal expression evaluates to itself, so no change in value (or metaata)

The expressoin whose value is bound to v2 is read as a list (vec (range 5)), and I am pretty sure that the reader should attach metadata to it at read time (not sure how to clearly show this at the REPL at the moment, though -- someone else may know). When that list expression is evaluated, it constructs a vector and returns it, but the vector created by vec does not have metadata on it.

I managed to get around it by downgrading ring to 1.8.4. Somehow this error only seems to happen on 1.9.2.

Possibly due to :join? false, causing your -dev-main fn to complete, and your server to be shut down.

Based on https://github.com/ring-clojure/ring/blob/master/ring-jetty-adapter/src/ring/adapter/jetty.clj#L170 it looks like you want :join? true with this usage

I don't think that's it, as the server was still running. I'd get an empty response with curl / wget, but the server was definitely reachable