indent-region is an act of editing a buffer. So before attempting to do that, it should be checked if the buffer is editable.
Bug#22819 raises that point.
The proposal is to call (barf-if-buffer-read-only) before attempting to do the indent.
Motive for this change:
The act of indenting is an editing action. So the buffer should be checked
if it's editable before attempting an indent. If the buffer is read-only
and no indentation change is required, then good. But what if indentation
change is required? Here's what's will happen:
1. User: Try indentation (C-x h M-x indent-region)
2. User: Could take several seconds or few minutes (depending on major mode
and file size)
3. Emacs: "Bummer, couldn't save all that indentation because the buffer is
4. User: Make buffer editable. It's not a simple act of chmod. In my case,
the buffer was read-only because the file is part of a centralized version
control system (Cliosoft SOS). In "checked in" state, the file is just a
symlink to the cached version in server, and thus read-only. To make it
editable, I need to "check out" the file. That act replaces the symlink
link with a physical file copy.
5. User: Re-do that several seconds/minutes long indentation.
So the motive is to save time and alert user of their pilot error before attempting to do an operation that would go to waste (in this case, doing indent, and then waste all those CPU cycles because the changes couldn't get saved to the file).
Question to the list:
- Are there any objections to doing the buffer read-only check before doing the indent?
(PS: If user's still want to do indentation on read-only buffers, then can always do C-x C-q (toggle read-only-mode) and then proceed to indent the buffer.)