Re: Bug or not a bug? dot expansion in ob-shell

[Bastien <bzg@gnu.org>]

Hi Eric,

note that the previous behavior only _seemed_ right by chance: there
is no notion of getting the exit code of the shell command in
ob-shell.el, and returning "0" is just a hazard here, just because
(org-babel--string-to-number ".") returns "0", while it should return
nil.

"Fraga, Eric" <e.fraga@ucl.ac.uk> writes:

> On Wednesday, 19 Feb 2020 at 12:38, Bastien wrote:
>> "0" is the _exit code_ of the successful echo command, not the value
>> returned by the echo command.
>
> But echo does not "return" the string as a value.  It outputs the
> string.
>
> To quote the man page for bash, "the return value of a simple command is
> its status".  Further, a function does not actually return any value
> beyond the status of the last command or a value given on a =return=
> statement.

Then we need to fix ob-shell.el to return the exit code of the last
command when :results is not set or explicitely set to "value".  Is
this something you want to look at?

Maybe by adding a "echo $?" instruction at the end of shell blocks
or by wrapping the code into something that returns the result?

I think it will come as a surprise for many users, since the natural
expectation seems to get the "output", disregarding bash notion of a
"return value".

I don't know.

> I disagree.  I think the current behaviour (i.e. before your attempt to
> "correct"" this) is correct given the documentation you quoted!

Yes, I see how it seems correct, but this was random...

>> Was it common to expect the exit code when executing shell code?
>
> Common?  I have no idea.  *I* did expect this.  But that's maybe because
> I do use the shell a lot.

I won't release 9.4 until we properly fix this, it's important.

> I think there's a clear distinction between value and output for src
> blocks and blurring this distinction for shell src blocks would be
> misleading.

Agreed.

> The option to request the output as the outcome of the src block is
> already there.

Yes, agreed again.

If you or someone else can look at ob-shell.el and see what can be
done to get the proper value (in bash's terms) of the last command in
the block, that'd be great.

Thanks!

-- 
 Bastien