[PATCH] Add new debug meta-command ,error

[Jose A. Ortega Ruiz]

* module/system/repl/debug.scm: <debug> stores the error string in a
  new field.
* module/system/repl/error-handling.scm: use the error string to
  construct the <debug> instance.
* module/system/repl/command.scm: new debug command `error' that
  extracts the new <debug> field.

Signed-off-by: Jose A. Ortega Ruiz <address@hidden>
---
 module/system/repl/command.scm        |   12 +++++++++---
 module/system/repl/debug.scm          |    4 ++--
 module/system/repl/error-handling.scm |   26 ++++++++++++++++----------
 3 files changed, 27 insertions(+), 15 deletions(-)

diff --git a/module/system/repl/command.scm b/module/system/repl/command.scm
index 8a62a16..52b0708 100644
--- a/module/system/repl/command.scm
+++ b/module/system/repl/command.scm
@@ -6,12 +6,12 @@
 ;; modify it under the terms of the GNU Lesser General Public
 ;; License as published by the Free Software Foundation; either
 ;; version 3 of the License, or (at your option) any later version.
-;; 
+;;
 ;; This library is distributed in the hope that it will be useful,
 ;; but WITHOUT ANY WARRANTY; without even the implied warranty of
 ;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 ;; Lesser General Public License for more details.
-;; 
+;;
 ;; You should have received a copy of the GNU Lesser General Public
 ;; License along with this library; if not, write to the Free Software
 ;; Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
@@ -55,7 +55,7 @@
              (disassemble x) (disassemble-file xx))
     (profile  (time t) (profile pr) (trace tr))
     (debug    (backtrace bt) (up) (down) (frame fr)
-              (procedure proc) (locals))
+              (procedure proc) (locals) (error e))
     (inspect  (inspect i) (pretty-print pp))
     (system   (gc) (statistics stat) (option o)
               (quit q continue cont))))
@@ -474,6 +474,12 @@ Trace execution."
                    body body* ...)
                  (format #t "Nothing to debug.~%"))))))))
 
+(define-meta-command (error repl)
+  "error
+Display the original error message."
+  (let ((debug (repl-debug repl)))
+     (format #t "~a~%" (if debug (debug-error-message debug) ""))))
+
 (define-stack-command (backtrace repl #:optional count
                                  #:key (width 72) full?)
   "backtrace [COUNT] [#:width W] [#:full? F]
diff --git a/module/system/repl/debug.scm b/module/system/repl/debug.scm
index 293b790..1876d31 100644
--- a/module/system/repl/debug.scm
+++ b/module/system/repl/debug.scm
@@ -30,7 +30,7 @@
   #:use-module ((system vm inspect) #:select ((inspect . %inspect)))
   #:use-module (system vm program)
   #:export (<debug>
-            make-debug debug? debug-frames debug-index
+            make-debug debug? debug-frames debug-index debug-error-message
             print-locals print-frame print-frames frame->module
             stack->vector narrow-stack->vector))
 
@@ -66,7 +66,7 @@
 ;;; accessors, and provides some helper functions.
 ;;;
 
-(define-record <debug> frames index)
+(define-record <debug> frames index error-message)
 
 
 
diff --git a/module/system/repl/error-handling.scm 
b/module/system/repl/error-handling.scm
index db0beeb..e77ea96 100644
--- a/module/system/repl/error-handling.scm
+++ b/module/system/repl/error-handling.scm
@@ -32,6 +32,16 @@
 ;;; Error handling via repl debugging
 ;;;
 
+(define (error-string stack key args)
+  (with-output-to-string
+    (lambda ()
+      (pmatch args
+        ((,subr ,msg ,args . ,rest)
+         (display-error (vector-ref stack 0) (current-output-port)
+                        subr msg args rest))
+        (else
+         (format #t "Throw to key `~a' with args `~s'." key args))))))
+
 (define* (call-with-error-handling thunk #:key
                                    (on-error 'debug) (post-error 'catch)
                                    (pass-keys '(quit)))
@@ -45,7 +55,7 @@
             (lambda ()
               (with-error-to-port err
                 thunk))))))
-    
+
     (catch #t
       (lambda () (%start-stack #t thunk))
 
@@ -75,7 +85,7 @@
          (if (procedure? post-error)
              post-error ; a handler proc
              (error "Unknown post-error strategy" post-error))))
-    
+
       (case on-error
         ((debug)
          (lambda (key . args)
@@ -85,22 +95,18 @@
                           (make-stack #t)
                           ;; Cut three frames from the top of the stack:
                           ;; make-stack, this one, and the throw handler.
-                          3 
+                          3
                           ;; Narrow the end of the stack to the most recent
                           ;; start-stack.
                           tag
                           ;; And one more frame, because %start-stack invoking
                           ;; the start-stack thunk has its own frame too.
                           0 (and tag 1)))
-                  (debug (make-debug stack 0)))
+                  (error-msg (error-string stack key args))
+                  (debug (make-debug stack 0 error-msg)))
              (with-saved-ports
               (lambda ()
-                (pmatch args
-                  ((,subr ,msg ,args . ,rest)
-                   (display-error (vector-ref stack 0) (current-output-port)
-                                  subr msg args rest))
-                  (else
-                   (format #t "Throw to key `~a' with args `~s'." key args)))
+                (format #t error-msg)
                 (format #t "Entering a new prompt.  ")
                 (format #t "Type `,bt' for a backtrace or `,q' to continue.\n")
                 ((@ (system repl repl) start-repl) #:debug debug))))))
-- 
1.7.1