From 229ea0e75b859fb33c8b71276112a625b941f734 Mon Sep 17 00:00:00 2001
From: Oleksandr Yakushev <alex@bytopia.org>
Date: Wed, 9 Apr 2025 19:47:45 +0300
Subject: [PATCH] [stacktrace] Add support for directly inspecting ex-data

---
 CHANGELOG.md                              |  1 +
 doc/modules/ROOT/pages/nrepl-api/ops.adoc |  3 ++-
 src/cider/nrepl.clj                       |  1 +
 src/cider/nrepl/middleware/stacktrace.clj | 28 +++++++++++++++--------
 4 files changed, 22 insertions(+), 11 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index c0663666f..bc06e9ec2 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,7 @@
 
 * Bump `orchard` to [0.33.0](https://github.com/clojure-emacs/orchard/blob/master/CHANGELOG.md#0330-2025-04-08).
 * [#929](https://github.com/clojure-emacs/cider-nrepl/pull/929): Migrate profiling middleware to orchard.profile.
+* [#930](https://github.com/clojure-emacs/cider-nrepl/pull/930): Stacktrace: add support for directly inspecting ex-data
 
 ## 0.54.0 (2025-04-05)
 
diff --git a/doc/modules/ROOT/pages/nrepl-api/ops.adoc b/doc/modules/ROOT/pages/nrepl-api/ops.adoc
index a4e220ad1..7fdc2da7b 100644
--- a/doc/modules/ROOT/pages/nrepl-api/ops.adoc
+++ b/doc/modules/ROOT/pages/nrepl-api/ops.adoc
@@ -475,7 +475,8 @@ Required parameters::
 
 
 Optional parameters::
-{blank}
+* `:ex-data` When equal to "true", inspect ex-data of the exception instead of full exception.
+
 
 Returns::
 * `:status` "done", or "no-error" if ``analyze-last-stacktrace`` wasn't called beforehand (or the ``index`` was out of bounds).
diff --git a/src/cider/nrepl.clj b/src/cider/nrepl.clj
index 3fd9c65ff..8ac05afc5 100644
--- a/src/cider/nrepl.clj
+++ b/src/cider/nrepl.clj
@@ -686,6 +686,7 @@ those configured directories will be honored."
               "inspect-last-exception" {:doc "Returns an Inspector response for the last exception that has been processed through `analyze-last-stacktrace` for the current nrepl session.
 Assumes that `analyze-last-stacktrace` has been called first, returning \"no-error\" otherwise."
                                         :requires {"index" "0 for inspecting the top-level exception, 1 for its ex-cause, 2 for its ex-cause's ex-cause, and so on."}
+                                        :optional {"ex-data" "When equal to \"true\", inspect ex-data of the exception instead of full exception."}
                                         :returns {"status" "\"done\", or \"no-error\" if `analyze-last-stacktrace` wasn't called beforehand (or the `index` was out of bounds)."
                                                   "value" "A value, as produced by the Inspector middleware."}}
               "stacktrace" {:doc "Return messages describing each cause and
diff --git a/src/cider/nrepl/middleware/stacktrace.clj b/src/cider/nrepl/middleware/stacktrace.clj
index 34d1bf3e0..d2341b609 100644
--- a/src/cider/nrepl/middleware/stacktrace.clj
+++ b/src/cider/nrepl/middleware/stacktrace.clj
@@ -17,13 +17,13 @@
 
 ;; Analyze the last stacktrace
 
-(def ^:dynamic *last-exception* nil)
-
 (defn- analyze-last-stacktrace
   "Analyze the last exception."
   [{:keys [session] :as msg}]
   (let [last-exception (@session #'*e)]
-    (swap! session assoc #'*last-exception* last-exception) ;; note that *e can change later, so this entry isn't redundant
+    ;; We need to remember the analyzed exception separately because we need to
+    ;; provide a way to inspect it while *e can change.
+    (alter-meta! session assoc ::analyzed-exception last-exception)
     (send-analysis msg (stacktrace/analyze last-exception))))
 
 (defn- handle-analyze-last-stacktrace-op
@@ -42,14 +42,22 @@
   (handle-analyze-last-stacktrace-op msg)
   (notify-client msg "The `stacktrace` op is deprecated, please use `analyze-last-stacktrace` instead." :warning))
 
+(defn- get-last-exception-cause [{:keys [session index] :as msg}]
+  (when index
+    (let [last-exception (::analyzed-exception (meta session))
+          causes (when last-exception
+                   (->> (iterate #(.getCause ^Throwable %) last-exception)
+                        (take-while some?)))]
+      (nth causes index nil))))
+
 (defn handle-inspect-last-exception-op [{:keys [session index transport] :as msg}]
-  (let [last-exception (@session #'*last-exception*)
-        causes (->> (iterate #(.getCause ^Throwable %) last-exception)
-                    (take-while some?))
-        cause (when index
-                (nth causes index nil))]
-    (if cause
-      (t/send transport (middleware.inspect/inspect-reply* msg cause))
+  (let [inspect-ex-data? (= (:ex-data msg) "true")
+        cause (get-last-exception-cause msg)
+        object (if inspect-ex-data?
+                 (ex-data cause)
+                 cause)]
+    (if object
+      (t/send transport (middleware.inspect/inspect-reply* msg object))
       (respond-to msg :status :no-error))
     (respond-to msg :status :done)))