Improved error reporting and handling

1 files changed, 5 insertions, 2 deletions

diff --git a/argot.lisp b/argot.lisp
index c2b3556..ec5f9b8 100644
--- a/argot.lisp
+++ b/argot.lisp
@@ -19,7 +19,9 @@
     :initform "")))
 
 (define-condition invalid-rule-def (error)
-  ((rule :reader rule :initarg :rule)))
+  ((rule :reader rule :initarg :rule))
+  (:report (lambda (e stream)
+             (format stream "The rule ~s is malformed." (car (rule e))))))
 
 (defun include-rule (grammar rule)
   (setf (gethash (rule-lhs rule) (grammar-rules grammar)) rule))
@@ -140,7 +142,8 @@ and it returns VAR in that case."
                                       :start-rule ',(first (first ruledefs))))
          ,@(loop
              :for ruledef :in ruledefs
-             :for (lhs pattern vars check action) := (parse-rule-def ruledef)
+             :for (lhs pattern vars check action) := (handler-case (parse-rule-def ruledef)
+                                                       (invalid-rule-def (e) (invoke-debugger e)))
              :for bindings := (collect-let-bindings lhs vars)
              :collect (rule-includer name lhs pattern check action bindings))