Re: : in the flow context for PyYAML and SnakeYAML

On 08/25/2010 04:11 PM, William Spitzak wrote:
> Kirill Simonov wrote:
>> Hi William,
>>
>> If you take a look at the function yaml_parser_scan_plain_scalar, lines
>> 3424-3433, you'll see:
>>
>> /* Check for 'x:x' in the flow context. TODO: Fix the test "spec-08-13". */
>>
>> if (parser->flow_level
>>          &&  CHECK(parser->buffer, ':')
>>          &&  !IS_BLANKZ_AT(parser->buffer, 1)) {
>>      yaml_parser_set_scanner_error(parser, "while scanning a plain scalar",
>>              start_mark, "found unexpected ':'");
>>      goto error;
>> }
>>
>> This condition is only checked in the flow context and it produces an
>> error if there is a colon followed by a non-whitespace character.
>
> You are right, my compiled version has that line commented out, as I had
> to fix it to read some JSON text. My personal opinion is that this MUST
> be changed. I had to fix it to read JSON output and I can't be the only
> one. There are VAST amounts of "unquoted" JSON out there, probably the
> majority! If YAML has any intention of being JSON-compatible it must fix
> this.

By unquoted JSON, do you mean something like:
     {foo:"bar"}

This is definitely not a valid JSON and I'm certain most of the JSON 
parsers will fail to parse it.  I'd say that an ability to parse this 
expression has nothing to do with JSON-compatibility, though you could 
claim it is Javascript-compatibility.

I believe both YAML 1.1 and 1.2 interpret this document as
     {'foo:"bar"': null}
PyYAML and libyaml producing an error is a stub; I intended to replace 
it with one interpretation or the other once I make up my mind. 
Producing an error allows me to choose the interpretation without 
breaking existing valid YAML documents.

> I have unfortunatly drifted away from YAML. I am using my patched
> version of the parser, but am not using any code for emitting it.
> Instead I wrote a much faster one which outputs YAML with "flow" turned
> on all the time, and with the ability to put newlines between the "flow"
> items. I quote everything containing any characters other than
> alphanumeric, period, underscore, +, or -.
>
> I am increasingly of the belief that a correct format would be more like
> JSON with optional quoting, with the addition of "type" and the addition
> of cross-references. Currently I am persuing this, though I am following
> the YAML discussion in case something interesting comes up.

Well, YAML is JSON with optional quoting, types, cross-references, and 
also block styles.


Thanks,
Kirill

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