Getting valid JSON output with xo(1)

[Matt Churchyard]

Thanks Stefan

For now I’ve altered my code to output the extra characters when needed,
and switch {} to [] using tr.

I may raise an issue with the libxo guys and see what happens, as it seems
to be a bit of a pain that I have to go through all this to generate a
fairly simple JSON document.

Matt
On Sun, 9 Sep 2018 at 17:13, Stefan Esser <se at freebsd.org> wrote:

> Am 09.09.18 um 16:10 schrieb Matt Churchyard:
> > Hi Stefan,
> >
> > I did include the commands used to generate the sample output in my first
> > message. I am using the xo(1) utility, not libxo directly. I did mention
> > this might not be the right list (you've obviously assumed I'm directly
> > using libxo), but it does seem to me this is more an issue with the xo
> > utility, rather than just a usage error.
>
> Hi Matt,
>
> I'm sorry - you are of course right and there was everything required to
> reproduce the effect in your previous mail ...
>
> > I've since looked further into the libxo documentation, and as you
> suggest,
> > it does seem that I need to be using the xo_open_list/xo_close_list
> > functions to generate the right output. However, these are not exposed
> via
> > xo(1). The documentation for xo_open_list describes how it is used to
> > create lists of individual entities, whereas the "l" modifier (which is
> all
> > I can access via xo(1)) creates "leaf lists", which are only for single
> > values. As such, it seems there's a big hole in the functionality of
> xo(1),
> > meaning it can only really be used to create very simple JSON documents.
>
> The following code fragment in libxo.c does suppress the terminating
> new-line
> character on purpose if depth != 0:
>
>     case XO_STYLE_JSON:
>         pre_nl = XOF_ISSET(xop, XOF_PRETTY) ? "\n" : "";
>         ppn = (xop->xo_depth <= 1) ? "\n" : "";
>
>         xo_depth_change(xop, name, -1, -1, XSS_CLOSE_CONTAINER, 0);
>         rc = xo_printf(xop, "%s%*s}%s", pre_nl, xo_indent(xop), "", ppn);
>         xop->xo_stack[xop->xo_depth].xs_flags |= XSF_NOT_FIRST;
>         break;
>
> The reason appears to be, that closing the outer level construct will print
> a new-line before other text. If you omit the second "xo --wrap",
> everything
> will look OK. And if you test with --depth 0, you'll see that the output is
> actually terminated with a new-line.
>
> > As I mentioned in my first message, it looks like xo(1) could do with
> some
> > way to open/close lists, similar to the --open/--close options, and a way
> > to specify that a single call should be output as a part of a list.
>
> I do not see a better solution than adding an "echo" command between calls
> to "xo --wrap", as you already mentioned as a work-around. This is simpler
> than adding list_open/close functions and it has the same effect, if you
> know that you are emitting JSON.
>
> Best regards, STefan
>