Re: Syntax errors in YAML blocks

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

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Thanks very much.

On Tue, 22 Jun 2021 at 17:56, John MacFarlane <jgm-TVLZxgkOlNX2fBVCVOL8/A@public.gmane.org> wrote:

> Fixed!
>
> William Lupton <wlupton-QSt+ys/nuMyEUIsrzH9SikB+6BGkLq7r@public.gmane.org> writes:
>
> > Thanks. https://github.com/jgm/pandoc/issues/7400
> >
> > On Mon, 21 Jun 2021 at 23:01, John MacFarlane <jgm-TVLZxgkOlNX2fBVCVOL8/A@public.gmane.org> wrote:
> >
> >>
> >> Yes, this definitely used to work.  Maybe due to the change to
> >> HsYAML? I will look into it, but an issue on the tracker will
> >> help ensure it doesn't get forgotten.
> >>
> >> BPJ <bpj-J3H7GcXPSITLoDKTGw+V6w@public.gmane.org> writes:
> >>
> >> > It used to work.
> >> >
> >> > Den mån 21 juni 2021 15:44William Lupton <wlupton@broadband-forum.org
> >
> >> > skrev:
> >> >
> >> >> All,
> >> >>
> >> >> I don't know how I missed this before, but I have noticed that this
> >> isn't
> >> >> treated as a valid YAML block (at least not with pandoc 2.11.4).
> >> >>
> >> >> *% *cat comment.md
> >> >>
> >> >> ---
> >> >>
> >> >> # comment
> >> >>
> >> >> ...
> >> >>
> >> >> *% *pandoc comment.md
> >> >>
> >> >> <hr />
> >> >>
> >> >> <h1 id="comment">comment</h1>
> >> >>
> >> >> <p>…</p>
> >> >>
> >> >> Inserting some YAML works:
> >> >>
> >> >> *% *cat comment-plus-variable.md
> >> >>
> >> >> ---
> >> >>
> >> >> # comment
> >> >>
> >> >> variable: 42
> >> >>
> >> >> ...
> >> >>
> >> >> *% *pandoc comment-plus-variable.md
> >> >>
> >> >>
> >> >>
> >> >> I realise that this is an abuse, and that I could have used an HTML
> >> >> comment (for example), but I believe that this is valid YAML, so
> should
> >> it
> >> >> have worked?
> >> >>
> >> >> *% *yq eval comment.md
> >> >>
> >> >>
> >> >>
> >> >> # comment
> >> >>
> >> >>
> >> >>
> >> >> *% *yq eval comment-plus-variable.md
> >> >>
> >> >> # comment
> >> >>
> >> >> variable: 42
> >> >>
> >> >> Apologies if this behaviour has changed in the latest pandoc...
> >> >>
> >> >> Thanks,
> >> >> William
> >> >>
> >> >> On Thu, 3 Jun 2021 at 09:10, William Lupton <
> >> wlupton-QSt+ys/nuMyEUIsrzH9SikB+6BGkLq7r@public.gmane.org>
> >> >> wrote:
> >> >>
> >> >>> 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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> >> >>>> .
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> >> >> <
> >>
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> >> >
> >> >> .
> >> >>
> >> >
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> >> .
> >>
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