From be6d8e95d1afd03ec7b43f3dc8c2338bcaaecf15 Mon Sep 17 00:00:00 2001
From: davidnolen <david.nolen@gmail.com>
Date: Sun, 6 Jul 2025 13:32:30 -0400
Subject: [PATCH] CLJS-3439: REPL doc support for externs * break out ->pre *
 add cljs.analyzer.api/resolve-extern * new doc lookup path in repl for js/foo
 symbols

---
 src/main/clojure/cljs/analyzer.cljc     | 5 ++++-
 src/main/clojure/cljs/analyzer/api.cljc | 9 +++++++++
 src/main/clojure/cljs/repl.cljc         | 5 +++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/src/main/clojure/cljs/analyzer.cljc b/src/main/clojure/cljs/analyzer.cljc
index 2a6364c8c..ac521fa78 100644
--- a/src/main/clojure/cljs/analyzer.cljc
+++ b/src/main/clojure/cljs/analyzer.cljc
@@ -977,10 +977,13 @@
        (or (= 'js x)
            (= "js" (namespace x)))))
 
+(defn ->pre [x]
+  (->> (string/split (name x) #"\.") (map symbol)))
+
 (defn normalize-js-tag [x]
   ;; if not 'js, assume constructor
   (if-not (= 'js x)
-    (let [props  (->> (string/split (name x) #"\.") (map symbol))
+    (let [props  (->pre x)
           [xs y] ((juxt butlast last) props)]
       (with-meta 'js
         {:prefix (vec (concat xs [(with-meta y {:ctor true})]))}))
diff --git a/src/main/clojure/cljs/analyzer/api.cljc b/src/main/clojure/cljs/analyzer/api.cljc
index 2d143a42b..2fa4f2a13 100644
--- a/src/main/clojure/cljs/analyzer/api.cljc
+++ b/src/main/clojure/cljs/analyzer/api.cljc
@@ -218,6 +218,15 @@
   ([state]
    (keys (get @state ::ana/namespaces))))
 
+(defn resolve-extern
+  "Given a symbol attempt to look it up in the provided externs"
+  ([sym]
+   (resolve-extern env/*compiler* sym))
+  ([state sym]
+   (let [pre (ana/->pre sym)]
+     (env/with-compiler-env state
+       (:info (ana/resolve-extern pre))))))
+
 (defn find-ns
   "Given a namespace return the corresponding namespace analysis map. Analagous
   to clojure.core/find-ns."
diff --git a/src/main/clojure/cljs/repl.cljc b/src/main/clojure/cljs/repl.cljc
index b5c53738a..b685a62e5 100644
--- a/src/main/clojure/cljs/repl.cljc
+++ b/src/main/clojure/cljs/repl.cljc
@@ -1447,6 +1447,11 @@ itself (not its value) is returned. The reader macro #'x expands to (var x)."}})
               (keyword? name)
               `(cljs.repl/print-doc {:spec ~name :doc (cljs.spec.alpha/describe ~name)})
 
+              (= "js" (namespace name))
+              `(cljs.repl/print-doc
+                 (quote ~(merge (select-keys (ana-api/resolve-extern name) [:doc :arglists])
+                           {:name name})))
+
               (ana-api/find-ns name)
               `(cljs.repl/print-doc
                  (quote ~(select-keys (ana-api/find-ns name) [:name :doc])))