Re: Syntax errors in YAML blocks

[BPJ <bpj-J3H7GcXPSITLoDKTGw+V6w@public.gmane.org>]

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It used to work.

Den mån 21 juni 2021 15:44William Lupton <wlupton-QSt+ys/nuMyEUIsrzH9SikB+6BGkLq7r@public.gmane.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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