It could be if go had a more powerful type system.

This isn’t a type system problem. It’s a data origin problem. Ie it could be any random JSON blob a user entered. The compiler doesn’t know this ahead of time.

If you wanted type safety with JSON in Go then don’t use the marshal interface. Period.

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thayne 5 hours ago | parent [-]

For unmarshalling, but the original complaint was about marshalling. And for that the type system could help if the marshal API only allowed you to marshal objects of types that supported marshalling.

And even for unmarshalling you could get a compile time error if you try to unmarshall to a type that doesn't support it.

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hnlmorg 4 hours ago | parent | next [-]

I’d already addressed that when I said the marshal API is an interface that’s meant to be reusable across generalise use cases. it can be used for a variety of data formats and not just JSON.

Go has this concept baked into the language. For example read and write interfaces so you can write data to an endpoint without having to worry about whether it’s a file system object, TCP/UDP socket, gzip achieve, and a plethora of other options too.

It’s a nice convenience feature and makes up considerably for the restrictions that the Go type system places.

And if you need higher performance code, or compile time safety, or have any other constraints that limit your ability to use these generalised interfaces, then you can use different APIs from the Go standard library to achieve the same thing.

You don’t need to call json.Marshal() if you don’t want to. It’s an option, but it’s just one API into the JSON toolbox.

	▲	thayne 3 hours ago \| parent [-]
		First of all, the json2 Marshall API is json specific. Secondly, other languages like rust, haskell, scala, etc. Have json APIs that are typesafe and give you compile time errors if you try to use a type that doesn't support (de) serialization . In the case of rust at least, the API is also general and can be used for other data types as well. Even in go, you could have some more type safety if Marshall took an interface (such as MarshallerTo) rather than `any`. Although then you have the problem of how you implement that interface. So I guess you probably want some kind of "derive" functionality, or macros that can approximate it for a convenient and type-safe API. P.S. gophers like to talk about how explicit being better than implicit, but using reflection for marshalling is very implicit.

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awesome_dude 40 minutes ago | parent | prev [-]

I'm confused by this - you're saying that a "type system" would address this, even though there are two (incompatible) type systems at play here - Go's and JSON's

Compile time cannot check for runtime values (not even in Rust) - is your position that fields can only be populated at compile time?