1. Keep 1.0 as a special case to maintain the int/float distinction (it's a float; calling it a fraction is kinda-of-a-lie).
2. Refuse to handle floats at all, at which point people can pass [ <mantissa>, <exponent> ] for reals or [ <numerator>, <denominator> ] for rationals.
There is of course (3), "build a compliance suite and claim the parsers that toss out information are Incorrect", but that doesn't seem compatible with your postel-ish goals.
This happens not to be correct. By specification JSON numbers are just a series of characters, arranged in a certain way: https://tools.ietf.org/html/rfc7159#section-6
In practice though many JSON parsers will parse non-integer numbers to floats.
> 2. Refuse to handle floats at all, at which point people can pass [ <mantissa>, <exponent> ] for reals or [ <numerator>, <denominator> ] for rationals.
This is a really interesting idea. If you're writing something that's super important like medical software it would probably be worth considering. However, my goals are just to make minimal changes that improve JSON some while still keeping it fairly readable, so I think that means I should stick with allowing `123.456` or whatever. I'd like to try to keep an open mind on this though.
I think all the parsers I've used inflate 1 to an int and 1.0 to a float ... that or they don't, and I just thought they did.
Either way, many thanks for the correction.