Re: Syntax errors in YAML blocks

[William Lupton <wlupton-QSt+ys/nuMyEUIsrzH9SikB+6BGkLq7r@public.gmane.org>]

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Thanks!

On Thu, 3 Jun 2021 at 05:49, John MacFarlane <jgm-TVLZxgkOlNX2fBVCVOL8/A@public.gmane.org> wrote:

>
> These are good suggestions.  I've revised the manual accordingly.
>
> BPJ <melroch-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> writes:
>
> > Perhaps it should be pointed out that the body of YAML block scalars must
> > be indented relative to the line with the `|` or `>`. Not doing so is
> > indeed a YAML syntax error, so Pandoc does the right thing when not
> > considering it valid YAML, however unfortunate it is that Pandoc may
> think
> > it is something else.
> >
> > The overview of YAML syntax on Wikipedia is quite good. Perhaps the
> manual
> > could link to (some specific version of) it.
> >
> > https://en.m.wikipedia.org/wiki/YAML#Syntax
> >
> > Den ons 2 juni 2021 21:21John MacFarlane <jgm-TVLZxgkOlNX2fBVCVOL8/A@public.gmane.org> skrev:
> >
> >>
> >> The problem is that basically anything is valid Markdown,
> >> it's just a matter of how it is interpreted.  It does seem
> >> to me that in the second case we might want to at least emit
> >> a warning -- if not downright fail.  It's just so unlikely
> >> that someone would write a block beginning with `---`
> >> and ending with `...` and intend it to be something other
> >> than YAML metadata.  If you'd like, you could submit an
> >> issue for this.  I'd rather not suggest avoiding complex
> >> YAML blocks -- sometimes they're fine, if the syntax is
> >> correct!
> >>
> >> William Lupton <wlupton-QSt+ys/nuMyEUIsrzH9SikB+6BGkLq7r@public.gmane.org> writes:
> >>
> >> > Thanks. Yes, I guess I realised it had something to do with ambiguous
> >> > grammars, but I hadn't really considered that my input was a valid
> table
> >> > (mea culpa).
> >> >
> >> > So I thought aha! I'll change the terminating "---" to "..." (in the
> hope
> >> > of an error), but this of course gives the output shown below.
> >> >
> >> > I wonder whether there could be a warning in the manual (or maybe
> there
> >> is
> >> > and I've missed it?) and/or perhaps a suggestion that it might be a
> good
> >> > idea to avoid complex YAML metadata blocks (in favour of metadata
> files)?
> >> > I'd be happy to create an issue and/or a MANUAL.md pull request.
> >> >
> >> > % cat bad.md
> >> > ---
> >> > history:
> >> > - number: Release 1.2
> >> >   changes: |
> >> >   - TBD
> >> > ...
> >> >
> >> > % pandoc bad.md
> >> > <hr />
> >> > <p>history: - number: Release 1.2 changes: | - TBD …</p>
> >> >
> >> >
> >> > On Wed, 2 Jun 2021 at 17:47, John MacFarlane <jgm-TVLZxgkOlNX2fBVCVOL8/A@public.gmane.org>
> wrote:
> >> >
> >> >>
> >> >> Well, this actually IS a valid "simple table".  So how is
> >> >> pandoc to know that you intended it as a YAML metadata block?
> >> >> Pandoc tries first to parse things as YAML blocks, and then as
> >> >> tables, if either works, the parse succeeds with no error.
> >> >>
> >> >> William Lupton <wlupton-QSt+ys/nuMyEUIsrzH9SikB+6BGkLq7r@public.gmane.org> writes:
> >> >>
> >> >> > Should I expect syntax errors in YAML blocks to be detected and
> >> reported?
> >> >> >
> >> >> > This has a syntax error in the YAML block:
> >> >> >
> >> >> > % cat bad.md
> >> >> > ---
> >> >> > history:
> >> >> > - number: Release 1.2
> >> >> >   changes: |
> >> >> >   - TBD
> >> >> > ---
> >> >> >
> >> >> > This fixes it:
> >> >> >
> >> >> > % diff bad.md good.md
> >> >> > 5c5
> >> >> > <   - TBD
> >> >> > ---
> >> >> >>     - TBD
> >> >> >
> >> >> > The latest pandoc:
> >> >> >
> >> >> > % ~/Downloads/pandoc-2.14.0.1/bin/pandoc -v
> >> >> > pandoc 2.14.0.1
> >> >> > ...
> >> >> >
> >> >> > Pandoc thinks the bad YAML is a table:
> >> >> >
> >> >> > % ~/Downloads/pandoc-2.14.0.1/bin/pandoc bad.md
> >> >> > <table>
> >> >> > <tbody>
> >> >> > <tr class="odd">
> >> >> > <td>history:</td>
> >> >> > </tr>
> >> >> > <tr class="even">
> >> >> > <td>- number: Release 1.2</td>
> >> >> > </tr>
> >> >> > <tr class="odd">
> >> >> > <td>changes: |</td>
> >> >> > </tr>
> >> >> > <tr class="even">
> >> >> > <td>- TBD</td>
> >> >> > </tr>
> >> >> > </tbody>
> >> >> > </table>
> >> >> >
> >> >> > But it's OK with the good YAML:
> >> >> >
> >> >> > % ~/Downloads/pandoc-2.14.0.1/bin/pandoc good.md
> >> >> >
> >> >> > Parsing the file as YAML reports the error:
> >> >> >
> >> >> > % ~/Downloads/pandoc-2.14.0.1/bin/pandoc --metadata-file bad.md
> >> >> > Error at "bad.md" (line 5, column 0):
> >> >> > Unexpected ' '
> >> >> >
> >> >> > % ~/Downloads/pandoc-2.14.0.1/bin/pandoc --metadata-file good.md
> >> >> > ^C
> >> >> >
> >> >> > --
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> >> >>
> >>
> https://groups.google.com/d/msgid/pandoc-discuss/CAEe_xxjF3Un2J-xg5UOs7uReZ5cO27TATA%2BfDY%2BAtghAsVhShA%40mail.gmail.com
> >> >> .
> >> >>
> >>
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> https://groups.google.com/d/msgid/pandoc-discuss/m2a6o8ul91.fsf%40johnmacfarlane.net
> >> .
> >>
> >
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