Is it possible to save undo state in file and reload again?

[Jean Louis]

There must exist some "undo" state in Emacs for {C-x u} to work,
right?

Is it maybe the contents of variable `pending-undo-list'?

I have tried saving it this way:

(defun data-to-file (data file)
  "PRIN1 Emacs Lisp DATA to FILE"
  (string-to-file-force (prin1-to-string data) file))

(defun data-from-file (file)
  "Reads and returns Emacs Lisp data from FILE"
  (condition-case nil
      (car (read-from-string
            (file-to-string file)))
    (error nil)))

(data-to-file pending-undo-list "pul") ➜ "pul"

(file-to-string "pul") works and I can see what is inside.

But then my function `data-from-file' can't handle it:

(data-from-file "pul")

because I get this error

(read-from-string (file-to-string "pul")) 
eval: Invalid read syntax: "#"

How can I save it in file and read from file with that read syntax
"#"? It should be somehow possible.

When editing database objects I would try to capture the undo state
and at any new editing to reload the undo state.


--
Jean

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