Built in JSON encoding/decoding is one of the things I’ve enjoyed about Swift. It’s nice when it’s not necessary to shop around for libraries for common needs like that.
Almost nobody is shopping around Rust JSON libraries unless they need some specific feature not provided by serde and serde_json. They are the default everyone reaches for.
The fact that a JSON parser is the sort of ecological niche where you naturally get a single best library which does basically what everyone wants it to do with minimal dependencies is exactly the argument for putting it in the stdlib, though.
That would require moving the entirety of serde and its traits (or equivalent) into the standard library. Considering how long it takes to stabilize basic things in the stdlib, I think that’s a terrible idea.
IMO Rust has the best tradeoff between stdlib and ecosystem libraries I’ve ever seen in a (compiled) language, and that includes serde/serde_json.
Based on your other reply about JSON being a "basic" feature I assume you do a lot of work with JSON.
What you need to understand is not everyone works with JSON, and for them it's a feature to not have JSON parsing code in their binaries. It's not a loss for them.
Where did you get a notion that JSON parsing code will end up in a binary if it’s not used? Or Rust compiler is so obtuse it can’t tree shake unused code?
How did you get that from what I said? JSON isn't included in Rust binaries because of its ability to bring in only what's needed, and my ability as a developer to specify that as a fine-gained level at compilation time.
Using a language where you don't bring things in as needed means they're built-in at the interpreter level or some other scheme like a large required standard library.
Maybe in those languages your compiler is smart enough to filter out unused code, maybe you don't even have a compiler and you have to distribute your code with an interpreter or a virtual machine with all the batteries. Either way, languages where libs are brought in as-needed are at an advantage when it comes to compiler tech to generate such binaries.
