Maps and Sets are entirely irrelevant when it comes to serialization. You may as well store or transmit that information as an array (of pairs, in case of Map). The point of a Map or Set (O(1) insertion / removal / contains) don't matter when you're talking about serialization.

Do you want remote code execution? Because that's how you get remote code execution. http://docs.couchdb.org/en/2.1.1/cve/2017-12635.html

Map and set values are important for many applications. The fact that JSON doesn't have a way of denoting a map or set value (or anything else, but that's another issue) is a problem: it means there's no understanding common to all JSON consumers about what syntax denotes a map or a set. Shortcuts are taken, consumers disagree on the details, and the linked CVE is the result. Being able to reliably convey "this is intended to be a map", or "this is intended to be a set" is crucial for secure and robust interoperability.

> Do you want remote code execution? Because that's how you get remote code execution.

It's fundamentally not the case that any data serialization format without support for map and set values allows for remote code execution. This CVE was CouchDB's auth code not handling some edge cases in the JSON standard.

Your argument that edge cases like this lead to problems is definitely a good one though. I'm more inclined to say that a lot of these kinds of issues are due to people thinking JSON is a simple, straightforward format when it definitely isn't -- and that's due to mostly two things:

- It fits on a business card!

- You can serialize/deserialize in one line in most implementations

Serialization/Deserialization is something you should always pay careful attention to. Making it a one-liner and advertising it as such was pretty irresponsible.

That's really weird - why didn't they parse it into a map in the first place, immediately removing duplicate keys? This seems like more of an argument for automatic deserializer generation than it does for adding undue complexity to a serialization format.

Even that's not enough to save you in general. JSON deliberately (!) permits duplicate keys. It leaves it up to the implementation to decide how to handle them.

And there are two (sensible) ways to add key/value pairs to a map: either keep the first occurrence of key X, or the last occurrence of key X.

Some JSON libraries pick one way; others pick the other.

Getting the two to interoperate is, as we see, not easy.

It would have been better for JSON to forbid duplicate keys, or to specify a mandatory first-wins or last-wins policy. Then there'd be no room for error.

Well, unlees you're using something like capnp, where O(1) contains is meaningful when O(n) deserialise is not acceptable.

And really, if you have consumers/producers in different languages/codebases, built-in support for these things is a great convenience. You wouldn't say that objects/dicts in JSON are irrelevant, would you?

> You wouldn't say that objects/dicts in JSON are irrelevant, would you?

I kind of would. Coming from Erlang, I don't see a point to there being a whole separate syntax for encoding object/map types. Just encode objects/maps as arrays of pairs (2-Tuples, or just length-2 arrays).

Then, if you want ser-des type fidelity, stick an annotation onto the array (like in YAML) to say what type it should decode to.

E.g., something like:

    [1, 2, 3] # array
    [['a', 1], ['b', 2], ['c', 3]] # array of pairs
    [@object, ['a', 1], ['b', 2], ['c', 3]] # array of pairs hinted so it should decode to an Object
    [@map, ['a', 1], ['b', 2], ['c', 3]] # array of pairs hinted so it should decode to a Map

The nice thing about this approach is that JSON libraries could do as much or as little work in parsing out the annotations as they want: they could recognize the annotations and construct the referred-to type; or they could just pass back the array with the annotation expressed as an Annotation value.

Do you know of Transit? https://github.com/cognitect/transit-format

Arbitrary precision integers is a JavaScript implementation detail; JSON standard doesn't specify number precision.

In theory, that is true. In practice, if the consuming client is javascript, it is really hard to map the numbers into an arbitrary precision number upon decoding (which would come from some library like big.js), rather than a pure double.

Which means, in practice, you are stuck passing numbers as strings (and on the javascript side, pass that string into the arbitrary precision number library)

Huh good to know:

  $ node
  > JSON.parse('1231231231231231231231231123123123123')
  1.2312312312312312e+36

I've heard of JSON implementations in other languages making bigger JSON numbers than javascript supports; but I didn't realise JSON.parse would quietly parse them and throw away precision in the process. I wonder what the plan is for JSON serialization support of bigints. I assume there is no plan - Chrome stable 67 supports bigints, but JSON.serialize(2n) throws a TypeError.

You might be interested in Zish https://github.com/tlocke/zish which has support for maps, timestamps, binary data and decimal types.

No need to extend json itself. But the libraries would need to be extended.

maps can be implemented with 1 array and 1 map, with the keys being the hash of the object. the hash function should probably be written in the Json itself for completeness.

embedded beinary blobs already work. lookup GLB for an example on how to embed binary blobs in Json.

as others said, json already supports arbitrary precision.

> embedded beinary blobs already work. lookup GLB for an example on how to embed binary blobs in Json.

Those aren't embedded binary blobs, those are string representations of base64-encoded binary blobs. Unless they come out of the JSON decoder as a byte array, they're not "working" as part of JSON; they're another standard on top of JSON.

(Also, the GP commenter probably wants them to be transmitted with 0 encoding overhead. Which can't really work while JSON is still JSON. But you can always use an alternative format which handles a superset of JSON's types, and which is binary, e.g. BSON or CBOR.)

> maps can be implemented with 1 array and 1 map, with the keys being the hash of the object. the hash function should probably be written in the Json itself for completeness.

I think you're fundamentally misunderstanding the thrust of the GP poster's request, here? They don't want to serialize a map in a way that is cheap to deserialize—different languages have different hashtable implementations so there's no way it could really work. What the GP poster (and many other people) want, is just to have something that encodes similarly to existing "object maps" (the ones with curly braces), but with a slight syntactic alteration so that they come out of the decoder as Maps, rather than as Objects.

I'm not talking about data URIs. You can write binary data in the same file as the json. Most parsers don't care what comes after the last curly brace.

I'm not an expert, just a bio-data-scientist learning every day... But wouldn't Yaml be what you are looking for?

Json is for machines, yaml is for humans, as a general rule. They’re mostly compatible feature-wise.

Yaml is well readable by a human but it's much to tightly defined to be "for humans". It's for machines but readable by humans I'd say. Plus it's got sets and you can embed csv's (just 2 things of the top of my head).

And if I remember correctly, YAML is a superset of JSON.

Obligatory link to the "YAML sucks" repo:

https://github.com/cblp/yaml-sucks

If you ignore the flame-inducing title, it's just a table showing how different implementations parse YAML input in very different ways.

you want to use protobufs

Another couple of missings:

- NaN/inf floats

- Comments

protobufs already support all these