Restart muffle-warning

Data Arguments Required:

None.

Description:

This restart is established by warn so that handlers of warning conditions have a way to tell warn that a warning has already been dealt with and that no further action is warranted.

Examples:

 (defvar *all-quiet* nil) → *ALL-QUIET*
 (defvar *saved-warnings* '()) → *SAVED-WARNINGS*
 (defun quiet-warning-handler (c)
   (when *all-quiet*
     (let ((r (find-restart 'muffle-warning c)))
       (when r 
         (push c *saved-warnings*)
         (invoke-restart r)))))
→ CUSTOM-WARNING-HANDLER
 (defmacro with-quiet-warnings (&body forms)
   `(let ((*all-quiet* t)
          (*saved-warnings* '()))
      (handler-bind ((warning #'quiet-warning-handler))
        ,@forms
        *saved-warnings*)))
→ WITH-QUIET-WARNINGS
 (setq saved
   (with-quiet-warnings
     (warn "Situation #1.")
     (let ((*all-quiet* nil))
       (warn "Situation #2."))
     (warn "Situation #3.")))
⊳ Warning: Situation #2.
→ (#<SIMPLE-WARNING 42744421> #<SIMPLE-WARNING 42744365>)
 (dolist (s saved) (format t "~&~A~%" s))
⊳ Situation #3.
⊳ Situation #1.
→ NIL

See Also:

Section 9.1.4.2 (Restarts), Section 9.1.4.2.2 (Interfaces to Restarts), invoke-restart, muffle-warning (function), warn