Propagate dispatcher signal

svn: r12683

collects/web-server/dispatchers/dispatch-servlets.ss

@@ -66,6 +66,7 @@
       (define response
         (with-handlers ([exn:fail:filesystem:exists?
                          (lambda (the-exn) (next-dispatcher))]
+                        [exn:dispatcher? raise]
                         [(lambda (x) #t)
                          (lambda (the-exn) (responders-servlet-loading uri the-exn))])
           (define the-servlet (url->servlet uri))
@@ -73,7 +74,8 @@
                          [current-custodian (servlet-custodian the-servlet)]
                          [current-directory (servlet-directory the-servlet)]
                          [current-namespace (servlet-namespace the-servlet)])
-            (with-handlers ([(lambda (x) #t)
+            (with-handlers ([exn:dispatcher? raise]
+                            [(lambda (x) #t)
                              (lambda (exn) (responders-servlet uri exn))])
               (call-with-continuation-barrier 
                (lambda ()

collects/web-server/scribblings/dispatchers.scrbl

@@ -368,7 +368,7 @@ a URL that refreshes the password file, servlet cache, etc.}
          dispatcher/c]{
  This dispatcher runs Scheme servlets, using @scheme[url->servlet] to resolve URLs to the underlying servlets.
  If servlets have errors loading, then @scheme[responders-servlet-loading] is used. Other errors are handled with
- @scheme[responders-servlet].
+ @scheme[responders-servlet]. If a servlet raises calls @scheme[next-dispatcher], then the signal is propagated by this dispatcher.
 }
                       
 }