Re: default :results

[Bastien <bzg@gnu.org>]

Hi Ian,

ian martins <ianxm@jhu.edu> writes:

> The doc says functional mode (=:results value=) is the default for
> most Babel libraries [1].  I haven't looked at many, but it is the
> default for ob-python and ob-shell. Scripting mode (=:results output
> =) is the default for ob-C, and the old ob-java (neither of these
> provided a functional mode).
>
> When I added functional mode to ob-java, I made it the default since
> that seemed correct.  But that change breaks anyone that relied on
> the old default (the workaround is to add a =:results output=
> header).  I will change the default in the short term to unbreak the
> experience, but what, if anything, should be done long term?

The default for ob-shell execution was to use the output, not the
value.  Then we had a long discussion, leading to this:

- The default (no :result) is to display the functional value

- For some languages, it may break expectations, so in this case we
  allow a variable that let the default (no :result) use the output
  instead of the functional value.

  This is what is being done for ob-shell.el where we have 
  `org-babel-shell-results-defaults-to-output' set to `t'.

See https://orgmode.org/list/877dt5trjr.fsf@bzg.fr/ for the conclusion
of the discussion.

Also see `org-babel-shell-results-defaults-to-output' docstring:

  Let shell execution defaults to ":results output".
  
  When set to t, use ":results output" when no :results setting
  is set.  This is especially useful for inline source blocks.
  
  When set to nil, stick to the convention of using :results value
  as the default setting when no :results is set, the "value" of
  a shell execution being its exit code.
  
> And is this inconsistent behavior across languages something that
> should be fixed? or is it intentional or at least not worth doing
> anything about?

What was suggested is to have a page on Worg listing the behavior of
various packages regarding block execution.

I started a section on https://orgmode.org/worg/library-of-babel.html
with a table -- feel free to add more to this table.

Thanks,

-- 
 Bastien