monkeypatching

monkeypatching.el

(defun su/monkeypatch/nil-fun (&rest args))
(defvar su/monkeypatch/nil-var nil)

(defun su/monkeypatch/mangle-name (symbol prefix)
  (concat "su/monkeypatches/" prefix (symbol-name symbol))
  )
(defun su/monkeypatch/copy-values (source-symbol dest-symbol)
  "This function copies values from source to dest. It does not keep any
  backups. I f you want that you want to use 'su/monkeypatch' instead"
  (ignore-errors
        (set dest-symbol (symbol-value source-symbol)))
  (ignore-errors
        (setplist dest-symbol (symbol-plist source-symbol)))
  (ignore-errors
        (fset dest-symbol (symbol-function source-symbol)))
  )

(defun su/monkeypatch (original-symbol substitute-symbol &optional prefix)
  "Monkey patch original with substitute. Uses the 'su/monkeypatches/' prefix to
save original binding"
  ;; Ok. Let's see how we'll go about this. We can use 'symbol-name' to convert
  ;; the quoted arguments into strings representing the symbols. Note that this
  ;; step will work even for bogus args. Then we can use intern-soft on those
  ;; strings to determine if they actually correspond to real names or not.
  (let* (
                 (cache-name (su/monkeypatch/mangle-name original-symbol prefix))
                 (cache-symbol (intern-soft cache-name))
                 (substitute-name (symbol-name substitute-symbol))
                 (substitute-symbol (intern-soft substitute-name))
                 )
        (if cache-symbol
                (su/debugging/print (format "Monkey-patch duplication detected in '%s'"
                                                                        cache-name) t)
          (if (not substitute-symbol)
                  (su/debugging/print (format "Unable to resolve substitute '%s' while \
  monkey-patching" substitute-name) t)
                (let ((cache-symbol (intern cache-name)))
                  ;; Checked conditions and are nowin a position to start caching old
                  ;; bindings
                  (su/monkeypatch/copy-values original-symbol cache-symbol)
                  ;; Now plug in new bindings
                  (su/monkeypatch/copy-values substitute-symbol original-symbol)
                ))
          )
        )
  )

(defun su/monkeypatch-undo (original-symbol &optional prefix)
  "Undo the monkey patching on original-symbol. Uses the 'su/monkeypatches/'
  prefix to save original binding"
  (let* (
                 (cache-name (su/monkeypatch/mangle-name original-symbol prefix))
                 (cache-symbol (intern-soft cache-name))
                 (original-name (symbol-name original-symbol))
                 (original-symbol (intern-soft original-symbol))
                 )
        (if (not (and cache-symbol original-symbol))
                (su/debugging/print (format "Unable to undo Monkey-patch on '%s'" original-name) t)
          (su/monkeypatch/copy-values cache-symbol original-symbol)
          (unintern cache-symbol nil)
          )
        )
  )