(error "End after end of buffer") while replacing strings in a region inside buffer

Question

I need to prepare org files like this

* firsth things
...

compress files

#+begin_src shell
tar cfzv {migration-date}/{client-id}from{start-date}to{finish-date}.tar.gz 1/{soc-id}/{client-id}/
#+end_src

more things

...

And i created this elisp function in porder to replace this strings "{strings}"

(defun fullfill-client-template (start end)
  "Adapt migration template in REGION START END to client."
  (interactive "r")
  (let ((tenant-id (read-from-minibuffer "tenant id: "))
        (soc-id (read-from-minibuffer "soc id: "))
        (client-id (read-from-minibuffer "client id: "))
        (migration-date (read-from-minibuffer "migration date: "))
        (start-date (read-from-minibuffer "start date: "))
        (finish-date (read-from-minibuffer "finish date: ")))
    (replace-string-in-region "{tenant-id}" tenant-id start end)
    (replace-string-in-region "{soc-id}" soc-id start end)
    (replace-string-in-region "{client-id}" client-id start end)
    (replace-string-in-region "{migration-date}" migration-date start end)
    (replace-string-in-region "{start-date}" start-date start end)
    (replace-string-in-region "{finish-date}" finish-date start end)
    (message (format "Migrate client: %s/%s/%s from: %s to %s at %s"
                    tenant-id soc-id client-id start-date finish-date migration-date))))

I get the following error:

Selecting only the section compress files

(error "End after end of buffer")

but when I use edebug the variables start and end are always the same:

    Result: "1"
Result: "2"

Result: "3"

Result: "4"

Result: "5"

Result: "6"

Result: "1"

Result: 23 (#o27, #x17, ?\C-w)

Result: 178 (#o262, #xb2, ?²)

Result: 1 (#o1, #x1, ?\C-a)

Result: "2"

Result: 23 (#o27, #x17, ?\C-w)

Result: 178 (#o262, #xb2, ?²)

Result: 1 (#o1, #x1, ?\C-a)

Result: "3"

Result: 23 (#o27, #x17, ?\C-w)

Result: 178 (#o262, #xb2, ?²)

Result: 2 (#o2, #x2, ?\C-b)

Result: "4"

Result: 23 (#o27, #x17, ?\C-w)

Result: 178 (#o262, #xb2, ?²)

error: "End after end of buffer"

file-truename: End after end of buffer

Answer 1

I think I see the problem. As you are making substitutions, the end of the region (178) does not correspond to a fixed place in the buffer, it moves about depending on the length of the replacement. As long as the buffer end is at point 178 or greater, the replacement succeeds. At some point, the buffer end becomes less than 178 and the replacement barfs.

A workaround is to add a bunch of text at the end of the buffer, so that never happens (which is why I didn't see it in my first attempt).

[This solution is wrong (although it would "work" in the case above, but it is not general enough) - see the EDIT for a correct solution, as suggested in the comment] A better solution is to recalculate the effective end of the region for every replacement to be the lesser of the two values end and the position at the end of the buffer. If the end of the buffer ever becomes less than end, we will only attempt to do the replacement within the restricted region:

  (defun fullfill-client-template (start end)
    "Adapt migration template in REGION START END to client."
    (interactive "r")
    (let ((tenant-id (read-from-minibuffer "tenant id: "))
          (soc-id (read-from-minibuffer "soc id: "))
          (client-id (read-from-minibuffer "client id: "))
          (migration-date (read-from-minibuffer "migration date: "))
          (start-date (read-from-minibuffer "start date: "))
          (finish-date (read-from-minibuffer "finish date: ")))
      (replace-string-in-region "{tenant-id}" tenant-id start (min end (buffer-end 1)))
      (replace-string-in-region "{soc-id}" soc-id start (min end (buffer-end 1)))
      (replace-string-in-region "{client-id}" client-id start (min end (buffer-end 1)))
      (replace-string-in-region "{migration-date}" migration-date start (min end (buffer-end 1)))
      (replace-string-in-region "{start-date}" start-date start (min end (buffer-end 1)))
      (replace-string-in-region "{finish-date}" finish-date start (min end (buffer-end 1)))
  (message (format "Migrate client: %s/%s/%s from: %s to %s at %s"
                  tenant-id soc-id client-id start-date finish-date migration-date))))

An even better way perhaps is to use a marker instead of an absolute position, but I have not gone down that path yet.

EDIT: As a comment points out, the above solution is incorrect. A marker solution could probably be made to work, but as the comment also points out, there is a better solution:

  (defun fullfill-client-template (start end)
    "Adapt migration template in REGION START END to client."
    (interactive "r")
    (let ((tenant-id (read-from-minibuffer "tenant id: "))
          (soc-id (read-from-minibuffer "soc id: "))
          (client-id (read-from-minibuffer "client id: "))
          (migration-date (read-from-minibuffer "migration date: "))
          (start-date (read-from-minibuffer "start date: "))
          (finish-date (read-from-minibuffer "finish date: ")))
      (save-restriction
        (narrow-to-region start end)
        (replace-string-in-region "{tenant-id}" tenant-id (point-min) (point-max))
        (replace-string-in-region "{soc-id}" soc-id (point-min) (point-max))
        (replace-string-in-region "{client-id}" client-id (point-min) (point-max))
        (replace-string-in-region "{migration-date}" migration-date (point-min) (point-max))
        (replace-string-in-region "{start-date}" start-date (point-min) (point-max))
        (replace-string-in-region "{finish-date}" finish-date (point-min) (point-max)))
  (message (format "Migrate client: %s/%s/%s from: %s to %s at %s"
                  tenant-id soc-id client-id start-date finish-date migration-date))))

Thanks to @Gilles 'SO- stop being evil' for the solution.