How to execute a command on the selection (shell-command-on-region) in evil mode, without losing the selection?

Question

I'd like to use shell-command-on-region on the region, in a way that keeps the selection, even in the case the length of the output changes, and works in regular emacs and in evil mode?

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Note, I've already asked this related question which is similar, just not dealing with selection: How to use an external command to modify selected words and lines?

Answer 1

This can be done, I managed to get it working (with help from @wasamasa), notes:

• The selection needs to be stored and restored.
• It's important to run (setq deactivate-mark nil) so emacs can restore the selection.
• Special handling is needed for evil-visual-line mode,
  (evil-visual-select ...) needs to be called.

Below is a wrapper for shell-command-on-region that handles re-selection.

(defun shell-command-on-region-and-select
    (start end command
           &optional output-buffer replace
           error-buffer display-error-buffer
           region-noncontiguous-p)
  "Wrapper for 'shell-command-on-region', re-selecting the output.

Useful when called with a selection, so it can be modified in-place"
  (interactive)
  (let ((buffer-size-init (buffer-size)))
    (shell-command-on-region
     start end command output-buffer replace
     error-buffer display-error-buffer
     region-noncontiguous-p)
    (setq deactivate-mark nil)
    (setq end (+ end (- (buffer-size) buffer-size-init)))
    (set-mark start)
    (goto-char end)
    (activate-mark)
    ;; needed for evil line mode
    (when (string= evil-state "visual")
      (when (eq (evil-visual-type) evil-visual-line)
        (evil-visual-select start end 'line)))))

Example call:

(shell-command-on-region-keep-region-and-select
 (region-beginning) (region-end)
 "tr A-Za-z a-zA-Z && echo ' extra text'")