`(:k m)` returns `nil` while `(identical? (first (keys m)) :k)` is `true` — two coexisting `Keyword` instances?

Mon, 11 May 2026 12:59:06 +0000

We're seeing what looks like a violation of the keyword-interning invariant in production. The bug is deterministic (repeats thousands of times in the same order on the same Aleph/Netty thread) and is cleared by recompiling the affected namespaces via nREPL.

(when (and (map? result) (nil? (:payload result)))   ; this WHEN fires
  (let [payload-key (->> (keys result)
                         (filter #(.contains (pr-str %) "payload"))
                         first)
        payload-via-key (when payload-key (get result payload-key))]
    (log/warn {:result-type                   (str (type result))
               :result-keys                   (pr-str (keys result))
               :payload-key-equals-literal?   (= payload-key :payload)
               :payload-key-identical?        (identical? payload-key :payload)
               :payload-via-found-key-nil?    (nil? payload-via-key)}
              "diagnostic")))

Logged values when the bug fires:

{:result-type                   clojure.lang.PersistentArrayMap
 :result-keys                   (:payload :aws-xray)
 :payload-key-equals-literal?   true
 :payload-key-identical?        true
 :payload-via-found-key-nil?    false}

So:

The (:payload result) in the when returned nil.
A few lines later, the diagnostic body proves that the first key in (keys result) IS the body-site :payload literal by identity (and therefore by =, since Keyword inherits Object.equals).
(get result that-key) returns the actual non-nil payload value.

PersistentArrayMap.indexOf uses == for Keyword keys, so the only way (:payload result) returns nil while (keys result) yields a key that is identical? to :payload at a nearby site is if the :payload literal at the WHEN site and the :payload literal at the body site are two different Keyword instances, even though they're written identically in one source-level function.

We compareed the :payload literal with the payload-key and found that both have -

identical content hashcode (-383036092)
identical name bytes [0x70 0x61 0x79 0x6C 0x6F 0x61 0x64]
identical codepoints
same classloader

so it really looks like two distinct interned Keyword instances with the same name.

Environment

Clojure 1.12.4
Eclipse Temurin JDK 25, Shenandoah GC, virtual threads enabled
ARM64 (AWS Graviton, ECS Fargate)
Aleph + Netty, transit-clj/transit-java for decoding

Questions

Could this be a bug in JVM / Clojure runtime?
Has similar behavior been seen in other cases?
What more evidence could we capture?

Add function that returns every interned keyword in the runtime

Wed, 07 Sep 2022 18:18:21 +0000

Having access to a list of every interned keyword in the runtime is useful for implementing editor auto-completion and other editor integration features.

Currently, most tooling does something like this:

user=> (let [field (.getDeclaredField clojure.lang.Keyword "table")] (.setAccessible field true) (map keyword (.keySet (.get field nil))))
(:target :clojure.main/message :clojure.spec.alpha/unknown :datafy :clojure.core.specs.alpha/prefix :dir :clojure.core.specs.alpha/binding-form :allow ...)

However, this approach relies on reflection to grab hold of a private, static field. The underlying bits are presumably (albeit unlikely) subject to change without notice.

Would it be possible to add a function into clojure.core that returns a list of all keywords in the runtime? Perhaps (all-keywords) (like (all-ns)). Or perhaps a public static method to clojure.lang.Keyword?

See also grep.app results for this pattern.

Clojure Q&A - Recent questions tagged runtime

`(:k m)` returns `nil` while `(identical? (first (keys m)) :k)` is `true` — two coexisting `Keyword` instances?

Environment

Questions

Add function that returns every interned keyword in the runtime