[print] Add custom print-method for throwables

Author: alexander-yakushev

src/orchard/print.clj

@@ -163,8 +163,20 @@
 (defmethod print TaggedLiteral [x w]
   (print-method x w))
 
-(defmethod print Throwable [x w]
-  (print-method x w))
+(defmethod print Throwable [^Throwable x, ^TruncatingStringWriter w]
+  (.write w "#Error[")
+  (.write w (str (.getName (class x)) " "))
+  (loop [cause x, msg nil]
+    (if cause
+      (recur (.getCause cause) (str msg (when msg ": ") (.getMessage cause)))
+      (print msg w)))
+  (when-let [data (not-empty (ex-data x))]
+    (.write w " ")
+    (print data w))
+  (when-let [first-frame (first (.getStackTrace x))]
+    (.write w " ")
+    (print (str first-frame) w))
+  (.write w "]"))
 
 (defmethod print :default [^Object x, ^TruncatingStringWriter w]
   (.write w (.toString x)))

test/orchard/print_test.clj

@@ -87,6 +87,11 @@
     "#Delay[<pending>]" (delay 1)
     "#Delay[1]" (doto (delay 1) deref)
     "#Delay[<failed>]" (let [d (delay (/ 1 0))] (try @d (catch Exception _)) d)
+    #"#Error\[clojure.lang.ExceptionInfo \"Boom\" \"orchard.print_test.+\"\]" (ex-info "Boom" {})
+    #"#Error\[clojure.lang.ExceptionInfo \"Boom\" \{:a 1\} \"orchard.print_test.+\"\]" (ex-info "Boom" {:a 1})
+    #"#Error\[java.lang.RuntimeException \"Runtime!\" \"orchard.print_test.+\"\]" (RuntimeException. "Runtime!")
+    #"#Error\[java.lang.RuntimeException \"Outer: Inner\" \"orchard.print_test.+\"\]" (RuntimeException. "Outer"
+                                                                                                         (RuntimeException. "Inner"))
     "#function[clojure.core/str]" str))
 
 (deftest print-writer-limits