Re: Possible bug with null document in libyaml

On Fri, Nov 20, 2009 at 8:22 PM, Osamu TAKEUCHI <[email protected]> wrote:

> Bill and Ingy,
>
> Thanks Ingy. I finally understood the importance of providing a way to
> serialize zero objects by reading your post. Before that, I was thinking as
> the same as Bill.
>
> Then, according to the spec, a YAML serializer can encode an empty string
> (in YAML 1.1 document) or a null object (in YAML 1.2 document) as an empty
> node in all the cases except for the one where the whole YAML stream becomes
> empty.
> I think an explicit warning should be given in the spec to clarify this
> point with some explanation of the
> importance of providing a way to serialize zero objects.
> It will be very much helpful.
>
> In addition, I point out that any empty string should not
> be encoded into empty nodes in YAML 1.1 document in any sense because it
> will not be compatible with YAML 1.2. In YAML 1.2 spec, an empty node
> represents a null object.
>

To put a finer point on it, an empty node parses as a plain, (unquoted)
empty string, scalar event. YAML loaders are encouraged (but not required)
to construct a null object from this event.

To be honest, I was not aware that this changed between 1.1 and 1.2. Can you
point me to the appropriate part of the spec that says this?

--Ingy


> So, anyways, all the YAML 1.1 serializers should be patched to encode all
> the empty strings in quoted styles "" or ''.
>
>
> BTW, I do not think a YAML 1.1 library will accept "x" as a valid YAML
> stream if the library strictly implements the specification. In YAML 1.1, a
> plain scalar node must be followed by s-l-comments that contains at least
> one line break. So, "x\n" is a valid document but "x" is not.
>
> This is the same problem pointed out for YAML 1.2 spec, first by Joshua
> Choi,
>
>
> http://sourceforge.net/mailarchive/forum.php?thread_name=200e06280904252219i1da33755h200bdac14058ba36%40mail.gmail.com&forum_name=yaml-core
>
> and then by me.
>
>
> http://sourceforge.net/mailarchive/forum.php?thread_name=1254356424.5043.224.camel%40nero&forum_name=yaml-core
>
> Probably, most of the real implementations ignore the spec to be compatible
> with hand-written documents possibly without a line break at the end. But,
> at least, a YAML serializer should not output a YAML document without a line
> break at the end.
>
> Best,
> Osamu Takeuchi
>
>

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