Re: [RFC] Do indent-region only on editable buffers

[Kaushal Modi <kaushal.modi@gmail.com>]

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On Mon, Aug 7, 2017 at 1:47 PM Drew Adams <drew.adams@oracle.com> wrote:

> > - Are there any objections to doing the buffer read-only check before
> >   doing the indent?
>
> Dunno what the right approach/solution is in this particular case.
>
> But note that we don't do what you suggest in general - we don't do it
> for most other editing operations: insert or delete a character, yank
> a string, kill the region,...  Instead, we let an error be raised,
> telling the user that the buffer is read-only.
>

This case feels a bit different because the operation can be very
expensive.. a few seconds or couple of minutes long indentation, based on
the major mode and file size. So a user would find it tremendously helpful
to know that the operation is useless on a read-only buffer before spending
that amount of time.

With the cases of insert/delete char, yank string, kill region, I have
never noticed any tangible delay (read: even a second).. so in those, it do
not matter if you "do and then flag error" or "flag an error and then do".

Also there are many cases of commands meant for buffer editing (like
keep-lines, flush-lines, etc.) where barf-if-buffer-read-only is used for
the same purpose.

The purpose of this email thread is to understand if there's a workflow
someone uses that would break if this read-only check were done at the
beginning of the indentation operation. As Eli states his concern in the
Bug#22819, do people rely on side-effects other than the actual
buffer-editing indentation operation?
-- 

Kaushal Modi

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