middleware.refresh: elide a lock for the "refresh-clear" op

Closes clojure-emacs/cider#3652
clojure-emacs · May 5, 2024 · c2a4fcb · c2a4fcb
1 parent b7aace8
commit c2a4fcb
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -16,6 +16,7 @@
 * Add `inspect-set-max-nested-depth` op that customizes how many nested levels the Inspector will print before abridging.
 * [#826](https://github.com/clojure-emacs/cider-nrepl/pull/826): Remove broken `inspect-get-path` middleware op, return path in every inspector middleware op instead.
 * Reduce the print length of values that CIDER debugger produces for overlay.
+* [cider#3652](https://github.com/clojure-emacs/cider/issues/3652) `middleware.refresh`: elide a lock for the `"refresh-clear"` op.
 
 ## 0.47.1 (2024-03-24)
 

diff --git a/src/cider/nrepl/middleware/refresh.clj b/src/cider/nrepl/middleware/refresh.clj
@@ -76,12 +76,18 @@
    msg]
   (reload-utils/after-reply error msg))
 
+(def ^{:added "0.48.0"} user-indicated-clear?
+  "Whether the user indicated that a `clear` is desired."
+  (atom false))
+
 (defn- refresh-reply
   [{:keys [dirs transport session id] :as msg}]
   (let [{:keys [exec]} (meta session)]
     (exec id
           (fn []
             (locking refresh-tracker
+              (when @user-indicated-clear?
+                (vreset! refresh-tracker (track/tracker)))
               (vswap! refresh-tracker
                       (fn [tracker]
                         (try
@@ -98,7 +104,10 @@
 
                           (catch Throwable e
                             (reload-utils/error-reply {:error e} msg)
-                            tracker))))))
+                            tracker)
+
+                          (finally
+                            (reset! user-indicated-clear? false)))))))
           (fn []
             (transport/send transport (response-for msg {:status :done}))))))
 
@@ -107,8 +116,10 @@
   (let [{:keys [exec]} (meta session)]
     (exec id
           (fn []
-            (locking refresh-tracker
-              (vreset! refresh-tracker (track/tracker))))
+            ;; This used to be a `locking`-based call to our `clear` implementation
+            ;; Now it merely "enqueues" a clearing, because the "refresh-clear" op is called synchronously by CIDER,
+            ;; so the `locking` could cause timeouts (https://github.com/clojure-emacs/cider/issues/3652 )
+            (reset! user-indicated-clear? true))
           (fn []
             (transport/send transport (response-for msg {:status :done}))))))