On Mon, Aug 7, 2017 at 3:55 PM Stefan Monnier <monnier@iro.umontreal.ca>
wrote:

> > The proposal is to call (barf-if-buffer-read-only) before attempting to
> do
> > the indent.
>
> No objection here.
>

Thanks.


> > 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 read-only". 4. User: Make
>
> Indentation of a region isn't done by computing the complete result and
> then "saving" it into the buffer.  So the error will be signaled as soon
> as the indent-region finds a line whose indentation should be changed.
> Usually that's almost instantaneous, but indeed in some cases it can
> take a while (e.g. in large regions that are already indented except for
> the last few lines).
>

Thanks for explaining the behavior. That explains why the read-only buffer
error is not thrown if the buffer is already indented.
-- 

Kaushal Modi