Re: [Json] The names within an object SHOULD be unique.

[Tatu Saloranta <[e-mail]>]

On Thu, Jun 6, 2013 at 9:40 AM, Vinny A <[e-mail]> wrote:

> On Jun 6, 2013, at 10:24 AM, Paul Hoffman <[e-mail]> wrote:
>
> The new text should use language that is already in RFC 4627; "key" is not
> such a word. To be fair to implementers, the new document also needs to
> deal with both emitters and parsers.
>
> Proposal:
>
> In Section 2.2:
> Current:
>   The names within an object SHOULD be unique.
> Proposed:
>   If the names within an object are not unique, the result of parsing the
>   object is unpredictable, and the parse may even fail completely. Thus,
>   the names within an object SHOULD be unique.
>
> In Section 4, add a new paragraph:
>   If a parser encounters an object with duplicate names, the parser MAY
>   fail to parse the JSON text; if the parser accepts objects with duplicate
>   names, it SHOULD accept only the last name/value pair that has the
>   duplicate name.
>
>
> If we have to recommend to both parsers and emitters, I'd like to make a
> slight change to your wording:
>
>
> In Section 2.2:
> Current:
>     The names within an object SHOULD be unique.
> Proposed:
>   * The names within an object SHOULD be unique. Non-unique keys have
> unpredictable effects (refer to sections 4 & 5).*
>
>
This sounds good.



> In Section 4 (Parsers) add a new paragraph:
>   *If a parser encounters an object with duplicate names, the parser
> MAY fail to parse the JSON text; if the parser accepts objects with
> duplicate names, it MUST accept only the last name/value pair that has the
> duplicate name. *
>
> In Section 5 (Generators) add a new paragraph:
> *   A JSON generator SHOULD not duplicate names. If duplicate names are
> generated, the authoritative name/value pair MUST be listed last.*
>


I find this problematic from streaming parsing perspective: if JSON content
is to be exposed as a stream of tokens, then this behavior is impractical
to implement. Even exposing just the first such key (or entry) is
problematic due to need to keep track of all seen keys. But at least it is
more practical than filtering out all but last.

Streaming parsing is the natural way to level processing, similar to XML
division of labor (SAX/Stax in Java, DOM/databind/XSLT on top), and
although more commonly used by frameworks and not end users, is an
important and common use case.

-+ Tatu +-