Re: Syntax errors in YAML blocks

[John MacFarlane <jgm-TVLZxgkOlNX2fBVCVOL8/A@public.gmane.org>]

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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>> >>>> >> >> .
>> >>>> >> >>
>> >>>> >>
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>> >>>> >> .
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