Re: [Pyparsing] jsonParser.py patch

[Paul M. <pt...@au...>]

Yes, I was too quick to read that part of the RFC, I was working just off
the content of json.org, which is a bit squishier on the format then the RFC
is.

If what we will get is JSON-text, then let's just call it jsonText, and
define it as:

jsonText = jsonObject | jsonArray
jsonText.ignore(jsonComment)

print jsonText.parseString(testdata)

And we should be confident now that jsonText matches the JSON-Text from the
RFC.

-- Paul


-----Original Message-----
From: pyp...@li...
[mailto:pyp...@li...] On Behalf Of thomas_h
Sent: Tuesday, April 22, 2008 4:47 PM
To: Paul McGuire
Cc: pyp...@li...
Subject: Re: [Pyparsing] jsonParser.py patch

Paul,

>  Hrm, well, I can see that this works, but I'm not sold.  A jsonObject 
> really
>  *isn't* a choice between a jsonDict and a jsonArray.  It really is a '{'
>  members '}', as per the BNF.  I think the real problem is elsewhere.

Yes, I wasn't very happy with my naming but I'm not very good at naming
anyway and I thought it would do. 'jsonObject' should probably be reserved
for what I named 'jsonDict', and what I named 'jsonObject'
should be called something else.

>  The RFC link you gave was very helpful.  It states that the content 
> of the  JSON string can be any JSON value, which you tripped over 
> because you  encountered a JSON array when we were parsing for a JSON
object.

I read this too, but wasn't sure I could trust my understanding.
Especially after I ran my current "reference implementation" (demjson) on a
file containing just "this is a value", which was dismissed as illegal.

The RFC defines (if I get it right) 'JSON-text' as the start symbol and says
"A JSON text is a serialized object or array.

      JSON-text = object / array".

That might speak in favor of my approach. I think the BNF (I presume you are
referring to the sidebar of json.org) supports your understanding as well
since there is no dedicated start symbol.
(Actually, I can't find that text again where it says JSON is just a JSON
value ...).

>
>  The solution is not to change the definition of jsonObject.  The 
> solution is  that we should have been invoking this:
>
>  jsonValue.parseString(testdata)

Fair enough. It might be overgenerating, though.

>  jsonValue already encompasses checking for all the different JSON 
> value  types - not just object and array, but also number, true, 
> false, etc.  Try  reverting to the original jsonParser.py, but change 
> this statement instead  and see if you get successful parsing.

I'm sure this will work, I'll give it a try.

Keep up,
Thomas

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