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by MobiusHorizons 325 days ago
Like it or not, but json data types are inherently linked to the primatives available in JavaScript. You can, of course write JSON that can’t be handled with the native types available in JavaScript, but the native parser will always deserialize to a native type. Until very recently all numbers were iee754 doubles in JavaScript, although arbitrary precision bignums do exist now. So the defacto precision limit of a number in JSON that needs to be compatible is an IEE754. If you control your clients you can do whatever you want though.
2 comments
jameshart 325 days ago
The standard definitely limits what precision you should expect to be handled.

But how JSON numbers are handled by different parsers might surprise you. This blog post actually does a good job of detailing the subtleties and the choices made in a few standard languages and libraries: https://github.com/bterlson/blog/blob/main/content/blog/what...

I think one particular surprise is that C# and Java standard parsers both use openAPI schema hints that a piece of data is of type ‘number’ to map the value to a decimal floating point type, not a binary one.

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xxs 324 days ago
>C# and Java standard parsers

Not sure which parser you consider standard, as Java doesn't have one at all (in the standard libraries). Other than that the existing ones just take the target type (not json) when they deserialize into, e.g. int, long, etc.

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jameshart 324 days ago
That blog post treats Jackson as the de facto standard Java JSON parser/formatter which seems reasonable.
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xxs 324 days ago
That's bit much - (unfortunately) the codebase uses at least 4 different json libraries (perhaps 5 if I consider one non-general purpose, personally written). gson is generally very popular as well. The blog post mentions BigDecimal and at that point, I'd not dare to trust it much.

The de-facto standard is similar to the expectation everyone uses spring boot.

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MangoToupe 324 days ago
> Like it or not, but json data types are inherently linked to the primatives available in JavaScript.

Presumably this is dependent on runtime. You certainly don't need to respect javascript (or any runtime's) parsers if you don't use javascript.

For instance, my current position explicitly uses arbitrary-precision decimals to deserialize json numbers.

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