[swift-evolution] [Proposal] Foundation Swift Encoders

[Itai Ferber]

The sorted order of keys is an implementation detail of 
`PropertyListSerialization` which `JSONSerialization` does not share.
This would require a change in `JSONSerialization`, which is possible, 
but out of scope for this work specifically. It would have to go through 
review.

[FWIW, the key ordering isn’t changing at random; `JSONSerialization` 
writes keys in the order that it receives them (sorted in the order that 
`NSDictionary` stores them, based on hash). If you want this to not 
interfere with your Git repo (on a more immediate timescale), you can 
probably do something like adding a pre-commit Git hook to lint the file 
as needed. But I digress, this is totally off-topic.]

On 16 Mar 2017, at 14:57, Ben Rimmington wrote:

> Sorry, I actually meant that keys would be ordered **alphabetically** 
> (as they are with PropertyListSerialization).
>
> I'm storing output from JSONSerialization in a git repository, and 
> when I add/remove a single key-value the entire file changes, due to 
> keys being reordered (seemingly at random).
>
> -- Ben
>
>> Itai Ferber wrote:
>>
>> By stable ordering, you mean dictionaries with keys being output in 
>> the order that they were encoded?
>> Potentially, but this would require additional work as neither Swift 
>> dictionaries nor NSMutableDictionary support this (reasonable seeing 
>> as dictionaries are by definition not sorted), and the current 
>> implementation uses JSONSerialization as the concrete serializer. 
>> Certainly not impossible, though.
>>
>>> On 16 Mar 2017, at 8:49, Ben Rimmington wrote:
>>>
>>> <https://github.com/apple/swift-evolution/pull/640>
>>>
>>> Could the `JSONEncoder.OutputFormatting.prettyPrinted` case include 
>>> the **stable ordering** of keys?
>>>
>>> -- Ben
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