Fancy printed exceptions if it's an asynchronous exception

[8sync.git] / eightsync / agenda.scm

diff --git a/eightsync/agenda.scm b/eightsync/agenda.scm
index 68db42eceee7bdb981612f594eacc0b4792c3568..2a431351af99b08ca06efed0c0afc03f28375f73 100644 (file)
--- a/eightsync/agenda.scm
+++ b/eightsync/agenda.scm
@@ -65,6 +65,14 @@
 
             %port-request %run %run-at %run-delay
             
+            catch-8sync catch-%8sync
+
+            ;; used for introspecting the error, but a method for making
+            ;; is not exposed
+            wrapped-exception?
+            wrapped-exception-key wrapped-exception-args
+            wrapped-exception-stacks
+
             print-error-and-continue
 
             %current-agenda
@@ -477,7 +485,7 @@ return the wrong thing via (%8sync) and trip themselves up."
 (define-syntax-rule (propagate-%async-exceptions body)
   (let ((body-result body))
     (if (wrapped-exception? body-result)
-        (throw '%8sync-caught-error
+        (throw '8sync-caught-error
                (wrapped-exception-key body-result)
                (wrapped-exception-args body-result)
                (wrapped-exception-stacks body-result))
@@ -510,10 +518,9 @@ return the wrong thing via (%8sync) and trip themselves up."
             ;; If something bad happened and we didn't catch it,
             ;; we'll wrap it up in such a way that the continuation
             ;; can address it
-            ;; @@: For this stack to work doesn't it have to be
             (lambda (key . args)
               (cond
-               ((eq? key '%8sync-caught-error)
+               ((eq? key '8sync-caught-error)
                 (match args
                   ((orig-key orig-args orig-stacks)
                    (make-wrapped-exception
@@ -543,6 +550,22 @@ return the wrong thing via (%8sync) and trip themselves up."
        (lambda ()
          body ...)))))
 
+(define-syntax-rule (catch-8sync exp (handler-key handler) ...)
+  (catch '8sync-caught-error
+    (lambda ()
+      exp)
+    (lambda (_ orig-key orig-args orig-stacks)
+      (cond
+       ((or (eq? handler-key #t)
+            (eq? orig-key handler-key))
+        (apply handler orig-stacks orig-args)) ...
+       (else (raise '8sync-caught-error
+                    orig-key orig-args orig-stacks))))))
+
+;; Alias...?
+(define-syntax-rule (catch-%8sync rest ...)
+  (catch-8sync rest ...))
+
 
 \f
 ;;; Execution of agenda, and current agenda
@@ -675,13 +698,29 @@ return the wrong thing via (%8sync) and trip themselves up."
              (agenda-queue agenda))
             (loop agenda))))))
 
-(define (print-error-and-continue . args)
+(define (print-error-and-continue key . args)
   "Frequently used as pre-unwind-handler for agenda"
-  (format (current-error-port) "\n*** Caught exception with arguments: ~s ***\n"
-          args)
-  (display-backtrace (make-stack #t 1 0)
-                     (current-error-port))
-  (newline (current-error-port)))
+  (cond
+   ((eq? key '8sync-caught-error)
+    (match args
+      ((orig-key orig-args stacks)
+       (display "\n*** Caught async exception. ***\n")
+       (format (current-error-port)
+               "* Original key '~s and arguments: ~s *\n"
+               orig-key orig-args)
+       (display "* Caught stacks below (ending with original) *\n\n")
+       (for-each
+        (lambda (s)
+          (display-backtrace s (current-error-port))
+          (newline (current-error-port)))
+        stacks))))
+   (else
+    (format (current-error-port)
+            "\n*** Caught exception with key '~s and arguments: ~s ***\n"
+            key args)
+    (display-backtrace (make-stack #t 1 0)
+                       (current-error-port))
+    (newline (current-error-port)))))
 
 (define-syntax-rule (maybe-catch-all (catch-handler pre-unwind-handler)
                                      body ...)