Common List: Use handler-case in different packages - common-lisp

Question

I've got the following lisp code :
;;; hop.lisp
(defpackage #:hop
(:use #:cl ))
(in-package :hop)
(export 'hop)
(defun hop ()
(restart-case
(error "Hop")
(hop ()
(format t "hop"))))
Where I define a dummy function that always fails but provides a restart : hop.
In another package, in this file :
;;; hip.lisp
(defpackage #:hip
(:use #:cl #:hop))
(in-package :hip)
(defun dhip ()
(hop:hop))
(defun hip ()
(handler-case
(hop:hop)
(error (e)
(declare (ignore e))
(format t "restarts: ~a~%" (compute-restarts))
(invoke-restart 'hop))))
I define the function (hip) and (dhip) that call the function (hop) from the first package.
When I call (dhip), sbcl offers me a prompt where I can choose to restart using my restart hop :
Hop
[Condition of type SIMPLE-ERROR]
Restarts:
0: [HOP] HOP
1: [RETRY] Retry SLIME REPL evaluation request.
2: [*ABORT] Return to SLIME's top level.
3: [ABORT] abort thread (#<THREAD "repl-thread" RUNNING {1009868103}>)
Backtrace:
0: (HOP)
1: (DHIP)
2: (SB-INT:SIMPLE-EVAL-IN-LEXENV (DHIP) #<NULL-LEXENV>)
3: (EVAL (DHIP))
--more--
Which is what I expected.
However, when I call (hip), my restart hop is not listed by (compute-restarts), and it fails to use it :(
No restart HOP is active.
[Condition of type SB-INT:SIMPLE-CONTROL-ERROR]
Restarts:
0: [RETRY] Retry SLIME REPL evaluation request.
1: [*ABORT] Return to SLIME's top level.
2: [ABORT] abort thread (#<THREAD "repl-thread" RUNNING {1009868103}>)
Backtrace:
0: (SB-INT:FIND-RESTART-OR-CONTROL-ERROR HOP NIL T)
1: (INVOKE-RESTART HOP)
2: ((FLET #:FUN1 :IN HIP) #<unused argument>)
3: (HIP)
4: (SB-INT:SIMPLE-EVAL-IN-LEXENV (HIP) #<NULL-LEXENV>)
5: (EVAL (HIP))
Do you know what can be done to make this works ?
Thanks,
Guillaule

Answer 1

This has nothing to do with the packages.
With HANDLER-CASE the stack is already unwound, when the handler runs. Thus the restart established in the function is gone.
Use HANDLER-BIND instead. It runs the handler in the context of the error and thus the restarts of the function are available.
Example:
(defun hip ()
(handler-bind ((error (lambda (e)
(declare (ignore e))
(format t "restarts: ~a~%" (compute-restarts))
(invoke-restart 'hop))))
(hop)))