Re: [boost] [review][JSON] json::value as a vocabulary type

On Sep 24, 2020, at 7:06 AM, Mike via Boost wrote:

Whether c++ is in need of a JSON vocabulary type and if Boost.JSON does provide a good one is a question I unfortunately can't answer yet (otherwise I'd have written a review), but imho the worth of that library should not just be measured by whether it is suited as a general vocabulary type for the whole c++ eco system, but if it provides a sound (doesn't necessarily need to be optimal) basis for building higher level libs on top of it in the future (inside and outside of boost). (e.g. implementing JSON based internet protocols).

This is anecdotal, of course, but within my company’s codebase the equivalent JSON-based variant structure is indeed used as a vocabulary type and passed between libraries - although of course they’re our own libraries, so it’s not really what you mean. It’s extremely convenient and its usage has become somewhat viral. We use Facebook’s `folly::dynamic` for that variant type today, and out of an average size (1M+ LOC) code base, the string “folly::dynamic” appears over 7,600 times. A lot of that usage is in unit test code+libraries, where we use the type for various purposes, but a lot of it is also in production code. It is *not* only used for when we need parsing or serialization to/from JSON, although certainly that’s a big usage too; and makes it even more convenient as a value type because we can serialize it to logs for debugging, or parse from strings/files for unit testing library APIs. Of course the downside with using such a dynamically-typed structure as a vocab type is it it won’t be as efficient as statically-typed ones, and if you put the wrong stuff in it you won’t get compile-time failures. But that’s an acceptable trade-off for some people/use-cases. -hadriel