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eval-print-last-sexp: "Selecting deleted buffer" error when the current
eval-print-last-sexp: "Selecting deleted buffer" error when the current buffer is killed evaluating the expression
Fri, 30 Jul 2021 00:55:51 +0200
I tumbled on the error in the subject, "Selecting deleted buffer",
evaluating the following line in the "*scratch*" buffer with C-j:
When the other buffer isn't read-only, suppose "*foo*" is selected
after killing the current buffer "*scratch*", the error "Selecting
deleted buffer" appears into the echo area and the return value of
the evaluation is printed into the other buffer "*foo*".
If the other buffer is "*Messages*", which is read-only, the error
"Buffer is read-only: #<buffer *Messages*>" will appear instead.
I'd like to discuss the possibility to enforce printing the output
either to the initial current buffer when eval-print-last-sexp has
been called, or to the echo area when the prefix '-' is given. If
the initial current buffer (aka standard-output) is killed, during
the evaluation of the expression, we fall back to the echo area as
the output medium.
I attach a patch as proof of concept.
Below there's a version of the current eval-print-last-sexp, as of
commit 7e8d1b08e3e23bc783cad10e620c2ebe6536965c, well commented:
(defun eval-print-last-sexp (&optional eval-last-sexp-arg-internal)
(let ((standard-output (current-buffer)))
;; This prints to `standard-output', aka `current-buffer'.
;; Since `eval-last-sexp-arg-internal' is always replaced with t
;; when nil, the expression's return value is printed to what is
;; the actual `current-buffer' after the evaluation is done. If
;; the initial buffer is killed, the current buffer is something
;; else after the evaluation. "Buffer is read-only" is given if
;; the `current-buffer' is read-only, otherwise the return value
;; is printed at whatever is the actual `current-buffer' cursor.
(eval-last-sexp (or eval-last-sexp-arg-internal t))
;; This prints to `standard-output', aka `current-buffer' before
;; the expression is evaluated. If the `standard-output' buffer
;; has been killed evaluating the expression, the PRINTPREPARE C
;; macro will trigger an error trying to `set-buffer' the killed
;; buffer: "Selecting deleted buffer".
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- eval-print-last-sexp: "Selecting deleted buffer" error when the current buffer is killed evaluating the expression,
Matthew White <=