Date: Sun, 9 Sep 2018 18:13:04 +0200 From: Stefan Esser <se@freebsd.org> To: Matt Churchyard <churchers@gmail.com>, freebsd-hackers@freebsd.org Subject: Re: Getting valid JSON output with xo(1) Message-ID: <228b2a88-6134-c8c2-a28d-cb09cbc03ef6@freebsd.org> In-Reply-To: <CANV9Nznba3ua_W17BnGOpiEcsW5pp-Jk4vFOcJxYnzVbUfWQ6w@mail.gmail.com> References: <CANV9Nz=3aOd5RM9KyTfz-1_%2BEnffKEOVQbYZxJY=i9_x0gorpA@mail.gmail.com> <ef40f50a-3a80-cc8d-5e9e-4bf40f8ff604@freebsd.org> <CANV9NzmyPoDk6qN19wW0SvzPu4aN9Ypsj9a_ttS2gp1EmqHUwQ@mail.gmail.com> <CANV9Nznba3ua_W17BnGOpiEcsW5pp-Jk4vFOcJxYnzVbUfWQ6w@mail.gmail.com>
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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
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