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json encoding of a map - order of members in an object #6244

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gopherbot opened this issue Aug 25, 2013 · 7 comments
Closed

json encoding of a map - order of members in an object #6244

gopherbot opened this issue Aug 25, 2013 · 7 comments
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@gopherbot
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by janh4lfar:

Object members should not be ordered:

From http://www.ietf.org/rfc/rfc4627.txt?number=4627

"... An object is an unordered collection of zero or more name/value
pairs, where a name is a string and a value is a string, number,
boolean, null, object, or array. ..."

In other words - do not object members by their names.

Expected behaviour as implemented in nodejs, php, chrome and firefox as reference:

> var test = {"BBB":"b", "AAA" : "a",
"CCC" : "c"}
undefined
> test
{ BBB: 'b', AAA: 'a', CCC: 'c' }
> JSON.stringify(test)
'{"BBB":"b","AAA":"a","CCC":"c"}'

A little go snippet:

testMap := make(map[string]string)
originalJsonBytes := []byte(`{"BBB":"b", "AAA" :
"a", "CCC" : "c"}`)
json.Unmarshal(originalJsonBytes, &testMap)
jsonBytes, _ := json.Marshal(testMap)
fmt.Println(testMap, string(jsonBytes))

// current output: json members are sorted by their name:
map[BBB:b AAA:a CCC:c]
{"AAA":"a","BBB":"b","CCC":"c"}

// right output to ensure interoperability - imho it should look like this:
map[BBB:b AAA:a CCC:c]
{"BBB":"b","AAA":"a","CCC":"c"}

The solution of the bug seems to be very simple - just remove sort.Sort(sv) in
src/pkg/encoding/json/encode.go in mapEncoder.encode() - obviously that might not be the
only place to look for ;)

Just by the way - I love this package!
@cznic
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cznic commented Aug 25, 2013

Comment 1:

IMO you've get the meaning of the word "unordered", as used in the referenced RFC,
wrong. The 'unordered' property of (a Javascript) object simply means that the below two
JSONs represent same object _values_:
        {"A": 1, "B": 2}
and
        {"B": 2, "A": 1}
IOW, proper interoperability IMO _must not_ depend on the order of the name/value pairs
in the JSON representation.

@bradfitz
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Comment 2:

Status changed to WorkingAsIntended.

@gopherbot
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Comment 3 by janh4lfar:

@0xj...
The honourable Douglas Crockford for sure could have been more precise. 
Assuming the order of your objects members is preserved - this is all you need to have
your top contributors of this week.
var topContributorsThisWeek = {
  "xxx@bar.com" : "For doing this",
  "aaa@foo.org"   : "Did that"
}
If not, you have to preserve the order in an extra object
var topContributorsThisWeek = {
  "contributors" : {
    "aaa@foo.org"   : "Did that",
    "xxx@bar.com" : "For doing this"
  },
  "order" : [
    "xxx@bar.com",
    "aaa@foo.org"
  ]
}
the "unordered" order of object members is like an implicit list - it is like buy two
get one for free ;)
Nazdar - Honza

@gopherbot
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Comment 4 by janh4lfar:

@bradfitz - that is sad to see please take a look at my last comment. Even if the JSON
spec is a little unspecific on this please consider, that JSON is there for
interoperability.

@gopherbot
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Comment 5 by janh4lfar:

The order of members in a JSON object matters - you can not just sort them
alphabetically. Just think of a list of country codes.

@gopherbot
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Comment 6 by janh4lfar:

http://play.golang.org/p/LL4euXjM7a

@bradfitz
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Comment 7:

Sorry, but you're just wrong here. JSON objects are unordered, just like Go maps.  If
you're depending on the order that a specific implementation serializes your JSON
objects in, you have a bug.

@golang golang locked and limited conversation to collaborators Jun 25, 2016
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@bradfitz @cznic @gopherbot