Re: org-src--contents-for-write-back : preserve original major-mode, and avoid mixing tabs and spaces in org-mode buffers

[Brent Goodrick <bgoodr@gmail.com>]

On Sat, Apr 29, 2017 at 2:59 AM, Nicolas Goaziou <mail@nicolasgoaziou.fr> wrote:
> Hello,
>
> Brent Goodrick <bgoodr@gmail.com> writes:
>
>> I do not understand what is meant by "tailored for the source" which
>> is the Org buffer. All of the indentation changes being made here are
>> within the temporary buffer created by with-temp-buffer, which is
>> using fundamental-mode which is not the same as either emacs-lisp-mode
>> or org-mode. That is the wrong mode to be in when running `indent-line-to`
>> function since it is that particular editing mode that the user has
>> control over the `indent-tabs-mode` variable (typically from mode hook
>> functions). So I conclude that the temporary buffer, at that point in
>> execution, has to be in the mode of the language used when indenting.
>
> This is not necessary. `org-src--contents-for-write-back' merely adds up
> indentation to the existing one.

Agreed.

> In particular, it doesn't re-indent
> lines. The indentation being added depends on Org mode (was the block in
> a list? Is it a src block where special indentation rules apply...), not
> on the major mode from the edit buffer.
>
> However, you have a point, as we need to somehow retain the values of
> `indent-tabs-mode' and `tab-width' from Org source buffer, since those
> may differ from the ones used in the temporary buffer.
>
> Also, calling `org-mode' again in the temporary buffer, in addition to
> being slow,

Yes, I wondered about the performance impact. Agreed.

> wouldn't preserve, e.g., local values from the source
> buffer. So I think the best thing to do is to store `indent-tabs-mode'
> and `tab-width' from source buffer and apply them back into the
> temporary buffer.
>
> I committed a change along those lines, along with tests, in the maint
> branch. Does it fix the issues you were encountering?

It works splendidly!

Thanks Nicolas.
--Brent