[inspect] Add dedicated inspector overload for exceptions

Author: alexander-yakushev

CHANGELOG.md

@@ -9,6 +9,7 @@
 * [#318](https://github.com/clojure-emacs/orchard/pull/318): **BREAKING:** Remove no longer used functions: `orchard.misc/lazy-seq?`, `orchard.misc/safe-count`, `orchard.misc/normalize-subclass`, `orchard.misc/remove-type-param`.
 * [#320](https://github.com/clojure-emacs/orchard/pull/320): Info: recognize printed Java classes/methods and munged Clojure functions in stacktrace outputs.
 * [#322](https://github.com/clojure-emacs/orchard/pull/322): Stacktrace: bring back `orchard.stacktrace` for stacktrace analysis (copied from `haystack.analyzer` and improved).
+* [#324](https://github.com/clojure-emacs/orchard/pull/324): Add dedicated renderers for exceptions to `orchard.print` and `orchard.inspect`.
 
 ## 0.30.1 (2025-02-24)
 

src/orchard/inspect.clj

@@ -62,6 +62,8 @@
     (instance? Class obj) :class
     (instance? clojure.lang.Namespace obj) :namespace
     (instance? clojure.lang.ARef obj) :aref
+    (instance? Throwable obj) :throwable
+    (instance? StackTraceElement obj) :stack-trace-element
     (.isArray (class obj)) :array
     :else (or (:inspector-tag (meta obj))
               (type obj))))
@@ -704,6 +706,50 @@
                                        (.toGenericString ^Method %)))
         (render-datafy))))
 
+(defn- render-stacktrace-cause [inspector ^Throwable cause]
+  (as-> inspector ins
+    (render-indent ins (.getMessage cause))
+    (render-ln ins)
+    (render-indent ins)
+    (render-value ins (class cause))
+    (if-let [first-frame (first (.getStackTrace cause))]
+      (-> ins
+          (render " at ")
+          (render-value first-frame))
+      ins)
+    (render-ln ins)
+    (if-let [data (not-empty (ex-data cause))]
+      (-> ins
+          (indent)
+          (render-value-maybe-expand data)
+          (unindent))
+      ins)))
+
+(defmethod inspect :throwable [inspector ^Throwable obj]
+  (let [causes (vec (take-while some? (iterate #(.getCause ^Throwable %) obj)))
+        root-cause ^Throwable (peek causes)]
+    (as-> inspector ins
+      (render-labeled-value ins "Class" (class obj))
+      (render-indent ins "Message: " (.getMessage obj))
+      (render-ln ins)
+      (render-section-header ins "Causes")
+      (indent ins)
+      (render-stacktrace-cause ins (first causes))
+      (reduce #(render-stacktrace-cause (render-ln %1) %2) ins (rest causes))
+      (unindent ins)
+      (render-section-header ins "Trace")
+      (indent ins)
+      (render-items ins (.getStackTrace root-cause) false 0 false)
+      (unindent ins)
+      (render-datafy ins))))
+
+(defmethod inspect :stack-trace-element [inspector ^StackTraceElement obj]
+  (-> inspector
+      (render-labeled-value "Class" (class obj))
+      (render-section-header "Contents")
+      (indent)
+      (render-items (StackTraceElement->vec obj) false 0 false)))
+
 (defmethod inspect :aref [inspector ^clojure.lang.ARef obj]
   (let [val (deref obj)]
     (-> (render-class-name inspector obj)

test/orchard/inspect_test.clj

@@ -1277,13 +1277,17 @@
         (is (match? '("Class: "
                       (:value "clojure.lang.ExceptionInfo" 0)
                       (:newline)
-                      "Value: "
-                      (:value
-                       "#error {\n :cause \"BOOM\"\n :data {}\n :via\n [{:type clojure.lang.ExceptionInfo\n   :message \"BOOM\"\n   :data {}}]\n :trace\n []}"
-                       1)
+                      "Message: " "BOOM"
                       (:newline)
                       (:newline))
                     (header rendered))))
+      (testing "renders a causes section"
+        (is (match? '("--- Causes:"
+                      (:newline)
+                      "  " "BOOM" (:newline)
+                      "  " (:value "clojure.lang.ExceptionInfo" 1) (:newline)
+                      (:newline))
+                    (section "Causes" rendered))))
       (testing "renders the datafy section"
         (is (match? (resolve-syms
                      (if (> java-api-version 8)
@@ -1321,7 +1325,33 @@
                          (:newline)
                          "  " (:value ":data" number?) " = " (:value "{}" number?)
                          (:newline))))
-                    (datafy-section rendered)))))))
+                    (datafy-section rendered))))))
+
+  (testing "exception with multiple causes"
+    (let [rendered (-> (ex-info "Outer" {} (RuntimeException. "Inner"))
+                       inspect render)]
+      (is (match? (resolve-syms
+                   '("--- Causes:"
+                     (:newline)
+                     "  " "Outer" (:newline)
+                     "  " (:value "clojure.lang.ExceptionInfo" number?) " at "
+                     (:value #"orchard.inspect_test\$fn" number?) (:newline)
+                     (:newline)
+                     "  " "Inner" (:newline) "  " (:value "java.lang.RuntimeException" number?) " at "
+                     (:value #"orchard.inspect_test\$fn" number?) (:newline)
+                     (:newline)))
+                  (section "Causes" rendered)))
+      (testing "trace is rendered"
+        (is (match? (matchers/prefix
+                     (resolve-syms
+                      '("--- Trace:"
+                        (:newline)
+                        "  " " 0" ". " (:value #"orchard.inspect_test\$fn" number?) (:newline)
+                        "  " " 1" ". " (:value #"orchard.inspect_test\$fn" number?) (:newline)
+                        "  " " 2" ". " (:value string? number?) (:newline)
+                        "  " " 3" ". " (:value string? number?) (:newline)
+                        "  " " 4" ". " (:value string? number?) (:newline))))
+                    (section "Trace" rendered)))))))
 
 (deftest inspect-eduction-test
   (testing "inspecting eduction shows its object fields"