I just ran our full suite of a few thousand unit tests with GOEXPERIMENT=jsonv2 and they all passed. (well, one test failed because an error message was changed, but that's on us)
I'm especially a fan of breaking out the syntactic part into into its own jsontext package. It makes a ton of sense, and I could see us implementing a couple parsers on top of that to get better performance where it really matters.
I wish they would take this chance to ditch omitempty in favor of just the newly-added omitzero (which is customizable with IsZero()), to which we'll be switching all our code over Real Soon Now. The two tags are so similar that it takes effort to decide between them.
I think the "omitempty" tag name might be too tarnished to keep around, but I think the distinction made between its redefined meaning and the new "omitzero" tag in v2 is quite useful:
- "omitempty" will omit an object field after encoding it, according to its JSON value
- "omitzero" will omit an object field before encoding it, according to its Go value
The former is particularly useful when you are dealing with foreign types that don't implement IsZero (yet) or implement it in an inappropriate way for how you're using it. You could, of course, write a wrapper type, but even when you can use struct embedding to make the wrapper less painful, you still have to duplicate all of the constructors/factories for that type, and you have to write the tedious code to do the conversions somewhere.
Those numbers look similar to goccy. I used to use it in the past, even Kubernetes uses it as direct dependency, but the amount of issues have been stockpiling for quite some time so I no longer trust it.
So it seems both are operating at the edge of Go's capabilities.
Personally, I think JSON should be in Go's core and highly optimised simd c code and not in the Go's std library as standard Go code. As JSON is such an important part of the web nowadays, it deserves to be treated with more care.
Previously Go team has been vocal about sacrificing performance to keep stdlib idiomatic and readable. Guess the crypto packages are the exception because they are used heavily by Google internally and json and some others (like say image/jpeg which had crap performance last time i checked) are not.
sonic uses a clang-generated ASM, built from C (transformed from normal clang-generated ASM to "weird" go ASM via python script)... I don't think this will be in standard library.
I think when it's introduced it might be worth discussing that again. Otherwise providing assembly for JSON of all packages seems like a huge maintenance burden for very little benefit for end users (since faster alternatives are readily available)
Agreed. goccy has better performance most times but absolutely appalling worst-case performance which renders it unacceptable for many use cases - in my case even with trusted input it took effectively eternity to decode it. It's literally a quadratic worst case, what's the point of having a bunch of super clever optimisations if the big-O performance is that bad.
Sonic may be different but I'm feeling once bitten twice shy on "faster" JSON parsers at this point. A highly optimised SIMD version might be nice but the stdlib json package needs to work for everything out there, not just the cases the author decided to test on, and I'd be a lot more nervous about something like that being sufficiently well tested given the extra complexity.
I don't recall either CORBA or SOAP ever seeing enough penetration to look "eternal" as mainstream tech goes (obviously, and especially with SOAP, there's still plenty of enterprise use). Unlike XML and JSON.
I hear you, but I am not aware of anyone that tried XMLHttpRequest.send('<s:Envelope xmlns:s...') or its '<methodCall>' friend from the browser. I think that's why they cited "of the web" and not "of RPC frameworks"
Eternal or not, right now JSON is used everywhere which means the performance gains of a more optimized Stalin would be significant. Just because we don’t know if JSON is around in 10 years doesn’t mean we should settle for burning extra compute on it.
The fact that JSON is used so commonly for web stuff seems like an argument against wasting your time optimizing it. Network round trip is almost always going to dominate.
If you're pushing data around on disk where the serialization library is your bottleneck, pick a better format.
You’re assuming request-response round trip between each call to encode/decode. Streaming large objects/NDJSON would still have serialization bottleneck. (See elasticsearch/opensearch for a real life use case)
But in that case your last point still stands: pick a better format
There is no better human-readable format. I looked. The only alternative i considered was Amazon Ion but it proved to bring no additional value compared to json.
This is an interesting perversion of Amdahl's law.
Yes, if you are looking at a single request-response interaction over the Internet in isolation and observing against wall clock time, the time spent on JSON (de-)serialization (unless egregiously atrocious) will usually be insignificant.
But that's just one perspective. If we look at CPU time instead of wall clock time, the JSON may dominate over the network calls. Moreover, in a language like Go, which can easily handle tens to hundreds of thousands of parked green threads waiting for network activity, the time spent on JSON can actually be a significant factor in request throughput. Even "just" doubling RPS from 10k to 20k would mean using half as much energy (or half as much cloud compute spend etc.) per request.
Changing formats (esp to a low-overhead binary one) might yield better performance still, but it will also have costs, both in time spent making the change (which could take months) and adapting to it (new tools, new log formats, new training, etc.).
IIRC, sonic does JIT, has inline assembly (github says 41%), and it's huge. There's no way you can audit it. If you don't need to squeeze every cpu cycle out of your json parser (and most of us don't; go wouldn't be the first choice for such performance anyway), I'd stick with a simpler implementation.
And Sonic with its "cutting edge" optimization is still slower than std Json on arm64 with basic use cases. It shows that JIT, simd, low level code comes at cost of maintenance for all platform.
first of all, that doesn't exercise JSON v2 at all, afaict
second of all, sonic apparently uses unsafe to (unsafe-ly) cast byte slices to strings, which of course is gonna be faster than doing things correctly, but is also of course incomparable to doing things correctly
like almost all benchmark data posted to hn -- unsound, ignore
Just using the GOEXPERIMENT=jsonv2 compiler flag changes the underlying implementation if you don't change any code. You're still using the less correct and efficient API though.
A bad design doesn't invalidate the sentence you have quoted.
Over time, it became evident that the JSON package didn't meet the needs of its users, and the package has evolved as a result. The size of the evolution doesn't matter.
"Becoming evident it doesn't meet the needs of its users" is not the same as "packages evolve with the needs of their users".
The latter is a weasely way to put the blame on changing needs - as if initially it was fine, but user needs grew and it's not covering them anymore. Truth is, user needs are the same, we havent had any magical change in JSON use patterns over the last 10 years. The design was just flawed to begin with.
I'd argue it didn't "become evident over time" either. It was evident on day one, and many people pointed it out 10 and 13 years ago.
It's true that packages (generally) evolve with the needs of their users.
It's also true that a json IO built-in lib typically wouldn't be so poorly designed in the first release of a language, that it would immediately be in need of maintenance.
Please don't use the "troll" accusation to something because you disagree with it. It's weasely.
Obviously encoding/json doesn't "work perfectly", the TFA lists several problems it has, and the need for a new version, and that's directly by the horse's mouth. Is the Go team "trolling" as well?
Second, we're not talking whether it "does the job", which is what you might mean by "works perfectly great".
We're talking about whether it's a good design for the problem domain, or whether it has footguns, bad API choices, performance problems, and other such issues.
Well mostly I have seem people learn shortcomings of software by using or creating it and come up with new version when possible. In your case it seems v1 are perfect each time.
I will say this and I feel it's true. Dealing with JSON in Go is a pain. You should be able to write json and not have to care about the marshalling and the unmarshalling. It's the way that serde rust behaves and more or less every other language I've had to deal with and it makes managing this behavior when there's multiple writers complicated.
The lack of tagged unions of some sort in go makes things like polymorphic json difficult to handle. It's possible, but requires a ton of overhead. Rust with enums mixed with serde makes this trivial. Insanely trivial.
Are you referring to the json macro that allows variable interpolation? Doing that will void type safety. Might be useful in dynamic languages like Python but I wouldn’t want to trade type safety for some syntactic sugar in Go
Please do run this on your own workloads! It's fairly easy to set up and run. I tried it a few weeks ago against a large test suite and saw huge perf benefits, but also found a memory allocation regression. In order for this v2 to be a polished release in 1.26, it needs a bit more testing.
I had a back and forth with someone who really didn't want to change that behavior and their reasoning was that since you can create and provide an empty map or slice.. having the marshaler do that for you, and then also needing a way to disable that behavior, was unnecessary complexity.
Not sure what you mean here by "most JavaScript parser rejects null" - did you mean "JSON parsers"? And why would they reject null, which is a valid JSON value?
It's more that when building an API that adheres to a specification, whether formal or informal, if the field is supposed to be a JSON array then it should be a JSON array. Not _sometimes_ a JSON array and _sometimes_ null, but always an array. That way clients consuming the JSON output can write code consuming that array without needing to be overly defensive
Well those are different things, aren't they? Empty slice/map is different from nil. So it makes a lot of sense that nil = null and []string{} = [], and you have an option to use both. That being said, it starts to make less sense if you work with go where the API mostly treats it as equivalent (append, len, []). So that would be my guess how it ended up the way it did.
Also, now that nil map is an empty object, shouldn't that extend to every nil struct that doesn't have a custom marshaller? It would be an object if it wasn't nil after all...
It is different from nil, but then again a nil map in Go behaves like an empty map when reading from it. If you consider serialization to be "reading", therefore, it makes sense to interpret it accordingly.
To be precise.. empty slices and maps sometimes behave like nil (len, range etc) and sometimes not (inserting into a nil map). The former is a neat convenience, and I think extending that to JSON marshaling makes sense.
Could somebody give a high level overview of this for me, as not a godev? It looks like Go JSON lib has support to encode native go structures in JSON, which is cool, but maybe it was bad, which is not as cool. Do I have that right?
Go already has a JSON parser and serializer. It kind of resembles the JS api where you push some objects into JSON.stringify and it serializes them. Or you push some string and get an object (or string etc) from JSON.parse.
The types themselves have a way to customize their own JSON conversion code. You could have a struct serialize itself to a string, an array, do weird gymnastics, whatever. The JSON module calls these custom implementations when available.
The current way of doing it is shit though. If you want to customize serialization, you need to return a json string basically. Then the serializer has to check if you actually managed to return something sane. You also have no idea if there were some JSON options. Maybe there is an indentation setting or whatever. No, you return a byte array.
Deserialization is also shit because a) again, no options. b) the parser has to send you a byte array to parse. Hey, I have this JSON string, parse it. If that JSON string is 100MB long, too bad, it has to be read completely and allocated again for you to work on because you can only accept a byte array to parse.
New API fixes these. They provide a Decoder or Encoder to you. These carry any options from top. And they also can stream data. So you can serialize your 10GB array value by value while the underlying writer writes it into disk for example. Instead of allocating all on memory first, as the older API forces you to.
There are other improvements too but the post mainly focuses on these so thats what I got from it (I havent tried the new api btw, this is all from the post so maybe I’m wrong on some points)
> If that JSON string is 100MB long, too bad, it has to be read completely and allocated again for you to work on because you can only accept a byte array to parse.
I was not sure whether this was the case, as `json.NewEncoder(io.Writer)` and `json.NewDecoder(io.Reader)` exist in v1, so I had checked, and guess what, you're right! Decode() actually reads the value to internal buffer before doing any marshalling in the first place. I had always assumed that it kept internal stack of some kind, for matching-parenthesis and type safety stuff within streaming context, but no, it doesn't do any of that stuff! Come think of it: it does make sense, as partial-unmarshal would be potentially devastating for incrementally-updated data structures as it would leave them to inconsistent state.
The largest problem were around behavior around nil in golang and what to convert into json and vice versa.
* The v2 will now throw an error for invalid characters outside of ut8 (before silently accepted it) which meant one had to preprocess or process again the json before sending it off to the server
* the golang nil will be converted to json empty array or map (for each type). previously it was converted to json null.
* json field names will be converted to golang names with case sensitivity. before it was case-insentitive and would be lowercased. this kinda caused lots of problems if the field collided. (say there's bankName and bankname in json)
* omitempty was problematic as it was used for say golang amount: nil would mean omit the field in json as {} instead of { amount: null}. however it also meant that the golang amount: 0 would also be omitted as { amount: 0 } which surprising. the new omitempty will only do so for nil and empty arrays/hashmaps but no longer for 0 or false. there's a new omitzero tag for that.
Nah, the existing implementation is pretty decent, actually, but doesn’t address every use case and has some flaws that are hard or impossible to fix. But for lots of use cases it works great.
Now here’s a new implantation that addresses some of the architectural problems that made the old library structurally problematic for some use cases (streaming large JSON docs being the main one).
I'm coming in a little hot and contrarian. I've been working with the Go JSON library for well over a decade at this point, since before Go 1.0, and I think v1 is basically fine.
I have two complaints. Its decoder is a little slow, PHP's decoder blows it out of the water. I also wish there was an easy "catch all" map you could add to a struct for items you didn't define but were passed.
None of the other things it "solves" have ever been a problem for me - and the "solution" here is a drastically more complicated API.
I frankly feel like doing a v2 is silly. Most of the things people want could be resolved with struct tags varying the behavior of the existing system while maintaining backwards compatibility.
My thoughts are basically as follows
The struct/slice merge issue? I don't think you should be decoding into a dirty struct or slice to begin with. Just declare it unsupported, undefined behavior and move on.
Durations as strings? Why? That's just gross.
Case sensitivity by default? Meh. Just add a case sensitivity struct tag. Easy to fix in v1
Partial decoding? This seems so niche it should just be a third party libraries job.
Basically everything could've been done in a backwards compatible way. I feel like Rob Pike would not be a fan of this at all, and it feels very un-Go.
I like the "does the problem justify the solution's complexity" question. The deserialization performance improvement seems like an actually important benefit though.
It is good to see some partial solutions to this issue. It plagues most languages and introduces a nice little ambiguity that is just trouble waiting to happen.
Ironically, JavaScript with its hilarious `null` and `undefined` does not have this problem.
Most JSON parsers and emitters in most languages should use a special value for "JSON null".
Null and undefined are fine imho with a sort of empty/missing semantics (especially since you mostly just care to == them) I have bigger issues to how similar yet different it is to have an undefined key and a not-defined key, I would almost prefer if
obj['key']=undefined
was the same as
delete obj['key']
Both v1 packages continue work; both are maintained. They get security updates, and were both improved by implementing them on top of v2 to the extent possible without breaking their respective APIs.
More importantly: the Go authors remain responsible for both the v1 and v2 packages.
What most people want to avoid with a "batteries included standard library" (and few additional dependencies) is the debacle we had just today with NPM.
Well maintained packages, from a handful of reputable sources, with predictable release schedules, a responsive security team and well specified security process.
You can't get that with 100s of independently developed dependencies.
It's not like this is new. Look at Java and .NET collection APIs, for example - both languages have the OG 1.0 versions, and then the more modern ones. In a similar vein, .NET has four different ways to deal with XML, of which three (XmlDocument, XPathDocument, and XDocument) are basically redundant representations of XML trees, each one doing things differently based on lessons learned.
I'm not sure how this is a problem, and I'm very sure that even in the presence of this "problem" it is far better for a language to have a batteries-included stdlib than to not
This V2 is still pushing forward the retarded behavior from v1 when it comes to handling nil for maps, slices and pointers. I am so sick and tired of this crap. I had to fork the v1 to make it behave properly and they still manage to fuck up completely new version just as well(by pushing omitempty and ignoring omitnil behavior as a standalone case) which means I will be stuck with the snale-pace slow v1 for ever.
"In v1, a nil Go slice or Go map is marshaled as a JSON null. In contrast, v2 marshals a nil Go slice or Go map as an empty JSON array or JSON object, respectively. The jsonv2.FormatNilSliceAsNull and jsonv2.FormatNilMapAsNull options control this behavior difference. To explicitly specify a Go struct field to use a particular representation for nil, either the `format:emitempty` or `format:emitnull` field option can be specified. Field-specified options take precedence over caller-specified options."
When you are unmarshaling json, empty map/slice is something completely different than a null or no value present, as you are losing intent of the sender, in case of JSON REST.
For example, if my intent is to keep the present value, I will send {"foo": 1} or {"foo": 1, "bar": null} as null and no value has the same meaning. On the other hand, I might want to change the existing value to empty one and send {"foo": 1, "bar": []}.
The server must understand case when I am not mutating the field and when I am mutating the field and setting it to be empty.
On the other side, I never want to be sending json out with null values as that is waste of traffic and provides no information to the client, ie {"foo": 1, "bar": null} is the same as {"foo": 1}.
Protocol buffers have the exact same problem but they tackle it in even dumber way by requiring you to list fields from the request, in the request's special field, which you are mutating as they are unable to distinguish null and no value present and will default to empty value otherwise, like {} or [], which is not the intent of the sender and causes all sort of data corruption.
PS: obviosly this applies to pointers as a whole, so if i have type Request struct { Number *int `json:"number"} then sending {} and {"number": null} must behave the same and result in Result{Number nil}
I still don't get how a common thing like JSON is not solved in go.
How convoluted it is to just get a payload from an api call compared to all languages is baffling
Love seeing meaningful stdlib improvements.
I just ran our full suite of a few thousand unit tests with GOEXPERIMENT=jsonv2 and they all passed. (well, one test failed because an error message was changed, but that's on us)
I'm especially a fan of breaking out the syntactic part into into its own jsontext package. It makes a ton of sense, and I could see us implementing a couple parsers on top of that to get better performance where it really matters.
I wish they would take this chance to ditch omitempty in favor of just the newly-added omitzero (which is customizable with IsZero()), to which we'll be switching all our code over Real Soon Now. The two tags are so similar that it takes effort to decide between them.
I think the "omitempty" tag name might be too tarnished to keep around, but I think the distinction made between its redefined meaning and the new "omitzero" tag in v2 is quite useful:
- "omitempty" will omit an object field after encoding it, according to its JSON value
- "omitzero" will omit an object field before encoding it, according to its Go value
The former is particularly useful when you are dealing with foreign types that don't implement IsZero (yet) or implement it in an inappropriate way for how you're using it. You could, of course, write a wrapper type, but even when you can use struct embedding to make the wrapper less painful, you still have to duplicate all of the constructors/factories for that type, and you have to write the tedious code to do the conversions somewhere.
Benchmark Analysis: Sonic vs Standard JSON vs JSON v2 in Go
https://github.com/centralci/go-benchmarks/tree/b647c45272c7...
Those numbers look similar to goccy. I used to use it in the past, even Kubernetes uses it as direct dependency, but the amount of issues have been stockpiling for quite some time so I no longer trust it.
So it seems both are operating at the edge of Go's capabilities.
Personally, I think JSON should be in Go's core and highly optimised simd c code and not in the Go's std library as standard Go code. As JSON is such an important part of the web nowadays, it deserves to be treated with more care.
What does "highly optimized" have to do with whether it's in the standard library? Highly-optimized cryptography is in the standard library.
Previously Go team has been vocal about sacrificing performance to keep stdlib idiomatic and readable. Guess the crypto packages are the exception because they are used heavily by Google internally and json and some others (like say image/jpeg which had crap performance last time i checked) are not.
Edit: See: https://go.dev/wiki/AssemblyPolicy
Not to mention that Go is never going to put C code in the standard library for anything portable. It's all Go or assembly now.
Which is the right approach, and one of the areas I actually appreciate the work of Go authors.
There is nothing special about C, other that its historical availability after UNIX's free beer came to be.
Any combination of high level + Assembly is enough.
It's amusing to see assembly considered more portable than C.
No, portable code is written in Go, not C. Platform specific code is written in ASM.
sonic uses a clang-generated ASM, built from C (transformed from normal clang-generated ASM to "weird" go ASM via python script)... I don't think this will be in standard library.
Go doesn't yet have native SIMD support, but it actually might in the future: https://github.com/golang/go/issues/73787
I think when it's introduced it might be worth discussing that again. Otherwise providing assembly for JSON of all packages seems like a huge maintenance burden for very little benefit for end users (since faster alternatives are readily available)
Agreed. goccy has better performance most times but absolutely appalling worst-case performance which renders it unacceptable for many use cases - in my case even with trusted input it took effectively eternity to decode it. It's literally a quadratic worst case, what's the point of having a bunch of super clever optimisations if the big-O performance is that bad.
Sonic may be different but I'm feeling once bitten twice shy on "faster" JSON parsers at this point. A highly optimised SIMD version might be nice but the stdlib json package needs to work for everything out there, not just the cases the author decided to test on, and I'd be a lot more nervous about something like that being sufficiently well tested given the extra complexity.
> As JSON is such an important part of the web nowadays, it deserves to be treated with more care.
There is a case to be made here but Corba, SOAP and XML-RPC likely looked similarly sticky and eternal in the past
I don't recall either CORBA or SOAP ever seeing enough penetration to look "eternal" as mainstream tech goes (obviously, and especially with SOAP, there's still plenty of enterprise use). Unlike XML and JSON.
They surely were, for anyone doing enterprise during the 2000's.
We had no plans to change to something else.
I hear you, but I am not aware of anyone that tried XMLHttpRequest.send('<s:Envelope xmlns:s...') or its '<methodCall>' friend from the browser. I think that's why they cited "of the web" and not "of RPC frameworks"
No, because that was server's job on the endpoint.
Eternal or not, right now JSON is used everywhere which means the performance gains of a more optimized Stalin would be significant. Just because we don’t know if JSON is around in 10 years doesn’t mean we should settle for burning extra compute on it.
The fact that JSON is used so commonly for web stuff seems like an argument against wasting your time optimizing it. Network round trip is almost always going to dominate.
If you're pushing data around on disk where the serialization library is your bottleneck, pick a better format.
You’re assuming request-response round trip between each call to encode/decode. Streaming large objects/NDJSON would still have serialization bottleneck. (See elasticsearch/opensearch for a real life use case)
But in that case your last point still stands: pick a better format
There is no better human-readable format. I looked. The only alternative i considered was Amazon Ion but it proved to bring no additional value compared to json.
This is an interesting perversion of Amdahl's law.
Yes, if you are looking at a single request-response interaction over the Internet in isolation and observing against wall clock time, the time spent on JSON (de-)serialization (unless egregiously atrocious) will usually be insignificant.
But that's just one perspective. If we look at CPU time instead of wall clock time, the JSON may dominate over the network calls. Moreover, in a language like Go, which can easily handle tens to hundreds of thousands of parked green threads waiting for network activity, the time spent on JSON can actually be a significant factor in request throughput. Even "just" doubling RPS from 10k to 20k would mean using half as much energy (or half as much cloud compute spend etc.) per request.
Changing formats (esp to a low-overhead binary one) might yield better performance still, but it will also have costs, both in time spent making the change (which could take months) and adapting to it (new tools, new log formats, new training, etc.).
If you're optimizing for energy wasted serving your website you could stop sending 10 megs of garbage javascript on page load.
IIRC, sonic does JIT, has inline assembly (github says 41%), and it's huge. There's no way you can audit it. If you don't need to squeeze every cpu cycle out of your json parser (and most of us don't; go wouldn't be the first choice for such performance anyway), I'd stick with a simpler implementation.
It also seems to need 4x the memory
And Sonic with its "cutting edge" optimization is still slower than std Json on arm64 with basic use cases. It shows that JIT, simd, low level code comes at cost of maintenance for all platform.
https://github.com/bytedance/sonic/issues/785
first of all, that doesn't exercise JSON v2 at all, afaict
second of all, sonic apparently uses unsafe to (unsafe-ly) cast byte slices to strings, which of course is gonna be faster than doing things correctly, but is also of course incomparable to doing things correctly
like almost all benchmark data posted to hn -- unsound, ignore
Just using the GOEXPERIMENT=jsonv2 compiler flag changes the underlying implementation if you don't change any code. You're still using the less correct and efficient API though.
>Over time, packages evolve with the needs of their users, and encoding/json is no exception
No, it's an exception. It was badly designed from the start - it's not just that people's json needs (which hardly changed) outgrew it.
A bad design doesn't invalidate the sentence you have quoted.
Over time, it became evident that the JSON package didn't meet the needs of its users, and the package has evolved as a result. The size of the evolution doesn't matter.
"Becoming evident it doesn't meet the needs of its users" is not the same as "packages evolve with the needs of their users".
The latter is a weasely way to put the blame on changing needs - as if initially it was fine, but user needs grew and it's not covering them anymore. Truth is, user needs are the same, we havent had any magical change in JSON use patterns over the last 10 years. The design was just flawed to begin with.
I'd argue it didn't "become evident over time" either. It was evident on day one, and many people pointed it out 10 and 13 years ago.
It's true that packages (generally) evolve with the needs of their users.
It's also true that a json IO built-in lib typically wouldn't be so poorly designed in the first release of a language, that it would immediately be in need of maintenance.
> immediately
JSON library released with Go 1, in 2012. This makes the library 13 years old [0].
If that's immediate, I'm fine with that kind of immediate.
[0]: https://pkg.go.dev/encoding/json@go1
"immediately be in need of maintenance" means it needed this update 13 years ago.
encoding/json works perfectly great even today, please troll somewhere else
Please don't use the "troll" accusation to something because you disagree with it. It's weasely.
Obviously encoding/json doesn't "work perfectly", the TFA lists several problems it has, and the need for a new version, and that's directly by the horse's mouth. Is the Go team "trolling" as well?
Second, we're not talking whether it "does the job", which is what you might mean by "works perfectly great".
We're talking about whether it's a good design for the problem domain, or whether it has footguns, bad API choices, performance problems, and other such issues.
It works well enough, despite being clunky, but it has a few issues, including significant performance-related ones.
In need of maintenance and having received maintenance are two different things
Well mostly I have seem people learn shortcomings of software by using or creating it and come up with new version when possible. In your case it seems v1 are perfect each time.
I will say this and I feel it's true. Dealing with JSON in Go is a pain. You should be able to write json and not have to care about the marshalling and the unmarshalling. It's the way that serde rust behaves and more or less every other language I've had to deal with and it makes managing this behavior when there's multiple writers complicated.
> serde rust
That does look a lot cleaner. I was just grumbling about this in golang yesterday (yaml, not json, but effectively the same problem).
I work in go every day and generally enjoy it.
The lack of tagged unions of some sort in go makes things like polymorphic json difficult to handle. It's possible, but requires a ton of overhead. Rust with enums mixed with serde makes this trivial. Insanely trivial.
Are you referring to the json macro that allows variable interpolation? Doing that will void type safety. Might be useful in dynamic languages like Python but I wouldn’t want to trade type safety for some syntactic sugar in Go
Please do run this on your own workloads! It's fairly easy to set up and run. I tried it a few weeks ago against a large test suite and saw huge perf benefits, but also found a memory allocation regression. In order for this v2 to be a polished release in 1.26, it needs a bit more testing.
> Since encoding/json marshals a nil slice or map as a JSON null
How did that make it into the v1 design?
I had a back and forth with someone who really didn't want to change that behavior and their reasoning was that since you can create and provide an empty map or slice.. having the marshaler do that for you, and then also needing a way to disable that behavior, was unnecessary complexity.
how is a nil map not null? It certainly isn’t a zero-valued map, that would be {}.
The zero value of a map is indeed nil in Go: This prints true (https://go.dev/play/p/8dXgo8y2KTh):
Ok, true!
It should be marshaled into {} by default, with a opt-out for special use cases.
There’s a simple reason: most JavaScript parsers reject null. At least in the slice case.
Not sure what you mean here by "most JavaScript parser rejects null" - did you mean "JSON parsers"? And why would they reject null, which is a valid JSON value?
It's more that when building an API that adheres to a specification, whether formal or informal, if the field is supposed to be a JSON array then it should be a JSON array. Not _sometimes_ a JSON array and _sometimes_ null, but always an array. That way clients consuming the JSON output can write code consuming that array without needing to be overly defensive
Well those are different things, aren't they? Empty slice/map is different from nil. So it makes a lot of sense that nil = null and []string{} = [], and you have an option to use both. That being said, it starts to make less sense if you work with go where the API mostly treats it as equivalent (append, len, []). So that would be my guess how it ended up the way it did.
Also, now that nil map is an empty object, shouldn't that extend to every nil struct that doesn't have a custom marshaller? It would be an object if it wasn't nil after all...
It is different from nil, but then again a nil map in Go behaves like an empty map when reading from it. If you consider serialization to be "reading", therefore, it makes sense to interpret it accordingly.
That is not true, though. Reading from a nil map panics, and reading from an empty map does not.
Why shouldn't it be? The nil is null and empty array is an empty array, they are completely different objects.
Not in Go. Empty slices and empty maps are nil, so it's ambiguous.
To be precise.. empty slices and maps sometimes behave like nil (len, range etc) and sometimes not (inserting into a nil map). The former is a neat convenience, and I think extending that to JSON marshaling makes sense.
No, empty slices and empty maps in Go are not nil.
This is the idiomatic way of declaring empty slices in Go, and it prints true:
This is indeed a nil slice, and it does have len() == 0, but Go also has a concept of empty slices separate from nil slices
The language just has a bad habit of confusing them some of the time, but not consistently, so you can still occasionally get bit by the difference
As someone who uses Go a lot, it's just one of those things...
Whether to judge the line below idiomatic, or not, is a question I leave to the authorities -- but it is highly convenient, and prints "false".
Yes because it's nil. You declared it but not created. Same for map. Same for var something *string
Could somebody give a high level overview of this for me, as not a godev? It looks like Go JSON lib has support to encode native go structures in JSON, which is cool, but maybe it was bad, which is not as cool. Do I have that right?
Go already has a JSON parser and serializer. It kind of resembles the JS api where you push some objects into JSON.stringify and it serializes them. Or you push some string and get an object (or string etc) from JSON.parse.
The types themselves have a way to customize their own JSON conversion code. You could have a struct serialize itself to a string, an array, do weird gymnastics, whatever. The JSON module calls these custom implementations when available.
The current way of doing it is shit though. If you want to customize serialization, you need to return a json string basically. Then the serializer has to check if you actually managed to return something sane. You also have no idea if there were some JSON options. Maybe there is an indentation setting or whatever. No, you return a byte array.
Deserialization is also shit because a) again, no options. b) the parser has to send you a byte array to parse. Hey, I have this JSON string, parse it. If that JSON string is 100MB long, too bad, it has to be read completely and allocated again for you to work on because you can only accept a byte array to parse.
New API fixes these. They provide a Decoder or Encoder to you. These carry any options from top. And they also can stream data. So you can serialize your 10GB array value by value while the underlying writer writes it into disk for example. Instead of allocating all on memory first, as the older API forces you to.
There are other improvements too but the post mainly focuses on these so thats what I got from it (I havent tried the new api btw, this is all from the post so maybe I’m wrong on some points)
gjson/sjson is probably for you if you need to work with 100MB JSONs.
This is cool. I wouldn't have thought to use Go for stuff that size.
> If that JSON string is 100MB long, too bad, it has to be read completely and allocated again for you to work on because you can only accept a byte array to parse.
I was not sure whether this was the case, as `json.NewEncoder(io.Writer)` and `json.NewDecoder(io.Reader)` exist in v1, so I had checked, and guess what, you're right! Decode() actually reads the value to internal buffer before doing any marshalling in the first place. I had always assumed that it kept internal stack of some kind, for matching-parenthesis and type safety stuff within streaming context, but no, it doesn't do any of that stuff! Come think of it: it does make sense, as partial-unmarshal would be potentially devastating for incrementally-updated data structures as it would leave them to inconsistent state.
The main issues are under the Behavior differences https://go.dev/blog/jsonv2-exp#behavior-differences
The largest problem were around behavior around nil in golang and what to convert into json and vice versa.
* The v2 will now throw an error for invalid characters outside of ut8 (before silently accepted it) which meant one had to preprocess or process again the json before sending it off to the server * the golang nil will be converted to json empty array or map (for each type). previously it was converted to json null. * json field names will be converted to golang names with case sensitivity. before it was case-insentitive and would be lowercased. this kinda caused lots of problems if the field collided. (say there's bankName and bankname in json) * omitempty was problematic as it was used for say golang amount: nil would mean omit the field in json as {} instead of { amount: null}. however it also meant that the golang amount: 0 would also be omitted as { amount: 0 } which surprising. the new omitempty will only do so for nil and empty arrays/hashmaps but no longer for 0 or false. there's a new omitzero tag for that.
Nah, the existing implementation is pretty decent, actually, but doesn’t address every use case and has some flaws that are hard or impossible to fix. But for lots of use cases it works great.
Now here’s a new implantation that addresses some of the architectural problems that made the old library structurally problematic for some use cases (streaming large JSON docs being the main one).
This. Having worked with it for over a decade the existing one is basically fine. Simple and clean interface.
New one solves some niche problems I think were probably just best left to third party libraries,
I'm coming in a little hot and contrarian. I've been working with the Go JSON library for well over a decade at this point, since before Go 1.0, and I think v1 is basically fine.
I have two complaints. Its decoder is a little slow, PHP's decoder blows it out of the water. I also wish there was an easy "catch all" map you could add to a struct for items you didn't define but were passed.
None of the other things it "solves" have ever been a problem for me - and the "solution" here is a drastically more complicated API.
I frankly feel like doing a v2 is silly. Most of the things people want could be resolved with struct tags varying the behavior of the existing system while maintaining backwards compatibility.
My thoughts are basically as follows
The struct/slice merge issue? I don't think you should be decoding into a dirty struct or slice to begin with. Just declare it unsupported, undefined behavior and move on.
Durations as strings? Why? That's just gross.
Case sensitivity by default? Meh. Just add a case sensitivity struct tag. Easy to fix in v1
Partial decoding? This seems so niche it should just be a third party libraries job.
Basically everything could've been done in a backwards compatible way. I feel like Rob Pike would not be a fan of this at all, and it feels very un-Go.
It goes against Go's whole worse is better angle.
I like the "does the problem justify the solution's complexity" question. The deserialization performance improvement seems like an actually important benefit though.
Also https://antonz.org/go-json-v2/#marshalwrite-and-unmarshalrea... not completely sure but maybe combining
dec := json.NewDecoder(in)
dec.Decode(&bob)
to just
json.UnmarshalRead(in, &bob)
is nicer...mostly the performance benefit though
> Durations as strings? Why? That's just gross
> It goes against Go's whole worse is better angle
One could almost say that durations as strings is...worse.
lol
If/once this goes through, I wonder what the adoption is going to be like now that all LLMs still only have the v1 api in their corpus.
Hopefully people will remember documentation exists once errors start popping up and refer to it.
null != nil !!!
It is good to see some partial solutions to this issue. It plagues most languages and introduces a nice little ambiguity that is just trouble waiting to happen.
Ironically, JavaScript with its hilarious `null` and `undefined` does not have this problem.
Most JSON parsers and emitters in most languages should use a special value for "JSON null".
Fixed in 1976 by ML, followed up by Eiffel in 2005, but unfortunately yet to be made common.
Null and undefined are fine imho with a sort of empty/missing semantics (especially since you mostly just care to == them) I have bigger issues to how similar yet different it is to have an undefined key and a not-defined key, I would almost prefer if
[dead]
This is the second time a v2 is released to a package in the Go's standard library. Other ecosystems are not free of this problem.
And then people complain that Rust doesn't have a batteries-included stdlib. It is done to avoid cases like this.
That has its own downsides, though.
Both v1 packages continue work; both are maintained. They get security updates, and were both improved by implementing them on top of v2 to the extent possible without breaking their respective APIs.
More importantly: the Go authors remain responsible for both the v1 and v2 packages.
What most people want to avoid with a "batteries included standard library" (and few additional dependencies) is the debacle we had just today with NPM.
Well maintained packages, from a handful of reputable sources, with predictable release schedules, a responsive security team and well specified security process.
You can't get that with 100s of independently developed dependencies.
Wow, two whole times in 19 years? That sounds terrible.
Yes, we should definitely go with the Rust approach instead.
Anyway, I'd better get back to figuring out which crate am I meant to be using...
I’d rather have 2 jsons in the stdlib after 15 years than 0 jsons in the stdlib
It's not like this is new. Look at Java and .NET collection APIs, for example - both languages have the OG 1.0 versions, and then the more modern ones. In a similar vein, .NET has four different ways to deal with XML, of which three (XmlDocument, XPathDocument, and XDocument) are basically redundant representations of XML trees, each one doing things differently based on lessons learned.
It's still better than the mess that is Node.js.
Two v2s in 15 years seems pretty good given the breadth of the stdlib.
I'm not sure how this is a problem, and I'm very sure that even in the presence of this "problem" it is far better for a language to have a batteries-included stdlib than to not
This V2 is still pushing forward the retarded behavior from v1 when it comes to handling nil for maps, slices and pointers. I am so sick and tired of this crap. I had to fork the v1 to make it behave properly and they still manage to fuck up completely new version just as well(by pushing omitempty and ignoring omitnil behavior as a standalone case) which means I will be stuck with the snale-pace slow v1 for ever.
Are you sure about that? Unless I'm misunderstanding they did fix this: https://pkg.go.dev/encoding/json
"In v1, a nil Go slice or Go map is marshaled as a JSON null. In contrast, v2 marshals a nil Go slice or Go map as an empty JSON array or JSON object, respectively. The jsonv2.FormatNilSliceAsNull and jsonv2.FormatNilMapAsNull options control this behavior difference. To explicitly specify a Go struct field to use a particular representation for nil, either the `format:emitempty` or `format:emitnull` field option can be specified. Field-specified options take precedence over caller-specified options."
What is your preferred behavior for a nil map/slice? Feels weird that it doesn't map to null.
When you are unmarshaling json, empty map/slice is something completely different than a null or no value present, as you are losing intent of the sender, in case of JSON REST.
For example, if my intent is to keep the present value, I will send {"foo": 1} or {"foo": 1, "bar": null} as null and no value has the same meaning. On the other hand, I might want to change the existing value to empty one and send {"foo": 1, "bar": []}.
The server must understand case when I am not mutating the field and when I am mutating the field and setting it to be empty.
On the other side, I never want to be sending json out with null values as that is waste of traffic and provides no information to the client, ie {"foo": 1, "bar": null} is the same as {"foo": 1}.
Protocol buffers have the exact same problem but they tackle it in even dumber way by requiring you to list fields from the request, in the request's special field, which you are mutating as they are unable to distinguish null and no value present and will default to empty value otherwise, like {} or [], which is not the intent of the sender and causes all sort of data corruption.
PS: obviosly this applies to pointers as a whole, so if i have type Request struct { Number *int `json:"number"} then sending {} and {"number": null} must behave the same and result in Result{Number nil}
Isn't that what the new 'omitzero' option is for?
https://pkg.go.dev/github.com/go-json-experiment/json#exampl...
you know you can make your case better if you don’t use disrespectful and offensive language
I still don't get how a common thing like JSON is not solved in go. How convoluted it is to just get a payload from an api call compared to all languages is baffling
> I still don't get how a common thing like JSON is not solved in go.
Given that it is not even yet solved in its namesake language, Javascript, that's not saying much.
You should read that, it's still relevant: https://seriot.ch/projects/parsing_json.html