Re: Last Call: <draft-ietf-appsawg-json-patch-08.txt> (JSON Patch) to Proposed Standard

[Pier-Luc Thériault <[e-mail]>]

>> Abstract
>>     JSON Patch defines the media type "application/json-patch", a JSON
>>     document structure for expressing a sequence of operations to apply
>>     to a JSON document, suitable for use with the HTTP PATCH method.
> ...
>> http://datatracker.ietf.org/doc/draft-ietf-appsawg-json-patch/
> I've reviewed JSON Patch and JSON Pointer as responsible AD, and am
> very happy with the documents -- this is good work, well written.  I
> came up with one issue that I want to discuss as part of last call:
>
>     4.1.  add
>
>     The "add" operation adds a new value at the target location.  The
>     operation object MUST contain a "value" member that specifies the
>     value to be added.
>
>     For example:
>
>     { "op": "add", "path": "/a/b/c", "value": [ "foo", "bar" ] }
>
>     When the operation is applied, the target location MUST reference one
>     of:
>
>     o  The root of the target document - whereupon the specified value
>        becomes the entire content of the target document.
>
> Now, what this means is that if we start with this:
>
> { "a": { "num": 1 } }
>
> and we apply this:
>
> { "op": "add", "path": "", "value": [ "foo", "bar" ] }
>
> we end up with this:
>
> [ "foo", "bar" ]
>
> This doesn't strike me as having any sense of an "add" operation -- it
> appears to be a special case that doesn't fit.  In any other
> situation, using any other path, the operation either adds something
> to what's already there, or it fails.  But when the path is "", it's
> anomalous.
>
> So, three questions:
>
> 1. Do I have this right, or am I mistaken about the result of that operation?
Yes, it's the good result
>
> 2. Assuming I have it right, can someone explain why it's this way?
It's the same as adding a value at any existing path
>
> 3. Can someone explain why this is the right way to specify it, rather
> than using "replace" for this?
It's not the right way, it's a right way. You can use replace to be sure 
that there's a root but there's always a root. Personally I would use 
replace
>
> Barry
>