Don't use with-exception-handler with (backtrace)

With with-exception-handler being called with #:unwind? #f (implicitly). This
breaks Guile internals used by (backtrace) [1], meaning you get a different
exception/backtrace when Guile itself breaks.

This should avoid the "string->number: Wrong type argument in position
1 (expecting string): #f" exception I've been haunted by for the last year.

1: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=46009

1 files changed, 12 insertions, 18 deletions

diff --git a/guix-build-coordinator/client-communication.scm b/guix-build-coordinator/client-communication.scm
index 580773b..4fdfade 100644
--- a/guix-build-coordinator/client-communication.scm
+++ b/guix-build-coordinator/client-communication.scm
@@ -380,27 +380,21 @@
 
   (with-exception-handler
       (lambda (exn)
-        (match method-and-path-components
-          ((method path-components ...)
-           (simple-format
-            (current-error-port)
-            "error: when processing client request: /~A ~A\n  ~A"
-            method (string-join path-components "/")
-            exn)))
         (render-json
-         `((error . ,(simple-format #f "~A" exn)))
+         `((error . 500))
          #:code 500))
     (lambda ()
-      (with-exception-handler
-          (lambda (exn)
-            (catch #t
-              (lambda ()
-                (backtrace))
-              (lambda (key . args)
-                (simple-format (current-error-port)
-                               "error: guile crashed printing backtrace\n")))
-            (raise-exception exn))
-        controller-thunk))
+      (with-throw-handler #t
+        controller-thunk
+        (lambda (key . args)
+          (match method-and-path-components
+            ((method path-components ...)
+             (simple-format
+              (current-error-port)
+              "error: when processing client request: /~A ~A\n  ~A ~A\n"
+              method (string-join path-components "/")
+              key args)))
+          (backtrace))))
     #:unwind? #t))
 
 (define* (render-json json #:key (extra-headers '())