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It's the type data that makes this hard: JSON has no support for encoding new types into the serialization. This is a blessing and a curse: it makes JSON simple, but also inflexible.

Take this parting remark:

> So, here’s another thing I wanna add to my suggestion: consider adapting ISO 8601 for a default JSON serialization of DateTime, so the following just works:

> var dt = DateTime.parse("2014-01-26T11:38:17");

> print(JSON.encode(dt));

Ignoring the fact that it's a simple value you're attempting to encode to JSON, let's say this works. Do you get:

Now do to the reverse: what does that decode to? Either it decodes to a string, and you've lost the type information, or it decodes to a date, in which case, what does `JSON.encode("2014-01-26T11:38:17")` decode to? i.e., do strings sometimes decode to dates? What if someone uses what should be a string to cause the decoder to decode it as a date? Now anywhere you have a string, it might decode to a date!

YAML has support for this sort of thing, with a syntax like `!!date "2014-01-26T11:38:17"`. (If you want a literal `!!`, it's always `"!!"`.) Notably, the Python library for YAML can do what the author asks: encode and decode arbitrary objects. (but it turns out to be a security risk to do so on untrusted data.)

> The Dart editor should be able to display a JSON serialization of anything the mouse pointer touches.

If my class contains a file handle, what's the JSON representation of a file handle? Further, if I send that serialization across the wire, how do you deserialize it? I mention this because you can't, at least, not really. Python's `repr` is a good example here. When it can, it gives you close-to Python syntax for the object, such as strings (`"hello world"`), ints (`1`), decimals (`Decimal(3)`), etc. Perfect for debugging. For things it can't, you get something like `<file object "~/foo.txt" at 0xdeadbeef>` — which doesn't parse (on purpose) as Python.

I'd venture to say that what you really want is the ability to introspect. Take your customer example: if you could introspect it, and see what member variables were present, you could build a function that might output:

  {"type": "Customer", {"Id": 1, "Name": "Joe Bob"}}
Again, note the explicit serialization of the type here, in JSON. This is something I made up, of course, and not JSON. Of course, some language feature can make introspection interesting. (Can you even get a list of members? Some languages allow objects to make up members on-the-fly.)

Hopefully, I've convinced you language design is hard. :-)

With enough static typing, or some sort of schema, none of this is a problem: all you need to do is to specify the type you're deserializing to. That said, it sounds like Dart is in trouble here due to other problems with its design (inheritance).

Well, there is a language that's perfectly suited to JSON serialization, and it has inheritance but not static-typing.

The point here is that designing a language around the current fashion in serialization is a bad idea. The problem as laid out in the article is unsolvable. A serialization format can automatically capture the semantics of a given language's native data structures, or it can easily interoperate with other languages, but not both.

JSON hits a sweet spot on the web because it captures a large subset of Javascript's data structures, while being simple and inflexible enough that other languages can work with it via libraries.

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