skir.build
Quick start: npx skir init
All the config lives in one YML file.
Website: https://skir.build
GitHub: https://github.com/gepheum/skir
Would love feedback especially from teams running mixed-language stacks.
1. Dense json
Interesting idea. You can also just keep the compact binary if you just tag each payload with a schema id (see Avro). This also allows a generic reader to decode any binary format by reading the schema and then interpreting the binary payload, which is really useful. A secondary benefit is you never ever misinterpret a payload. I have seen bugs with protobufs misinterpreted since there is no connection handshake and interpretation is akin to 'cast'.
2. Compatibility checks
+100 there's not reason to allow breaking changes by default
3. Adding fields to a type: should you have to update all call sites?
I'm not so sure this is the right default. If I add a field to a core type used by 10 services, this requires rebuilding and deploying all of them.
4. enum looks great. what about backcompat when adding new enum fields? or sometimes when you need to 'upgrade' an atomic to an enum?
0. Yes, I looked at Avro, Ion. I like Protobuf much better because I think using field numbers for field identity, meaning being able to rename fields freely, is a must.
1. Yes. Skir also supports that with binary format (you can serialize and deserialize a Skir schema to JSON, which then allows you to convert from binary format to readable JSON). It just requires to build many layers of extra tooling which can be painful. For example, if you store your data in some SQL engine X, you won't be able to quickly visualize your data with a simple SELECT statement, you need to build the tooling which will allow you to visualize the data. Now dense JSON is obviously not idea for this use case, because you don't see the field names, but for quick debugging I find it's "good enough".
3. I agree there are definitely cases where it can be painful, but I think the cases where it actually is helpful are more numerous. One thing worth noting is that you can "opt-out" of this feature by using `ClassName.partial(...)` instead of `ClassName()` at construction time. See for example `User.partial(...)` here: https://skir.build/docs/python#frozen-structs I mostly added this feature for unit tests, where you want to easily create some objects with only some fields set and not be bothered if new fields are added to the schema.
4. Good question. I guess you mean "forward compatibility": you add a new field to the enum, not all binaries are deployed at the same time, and some old binary encounters the new enum it doesn't know about? I do like Protobuf does: I default to the UNKNOWN enum. More on this: - https://skir.build/docs/schema-evolution#adding-variants-to-... - https://skir.build/docs/schema-evolution#default-behavior-dr... - https://skir.build/docs/protobuf#implicit-unknown-variant
avro supports field renames though.
3. on second thought i believe you'd only have to deploy when you choose. the next build will force you to provide values (or opt into the default). so forcing inspection of construction sites seems good.
> Cap'n Web is a spiritual sibling to Cap'n Proto (and is created by the same author), but designed to play nice in the web stack.
It's just JSON, which has up and down sides. But things like promise pipelining are such a huge upside versus everything else: you can refer to results (and maybe send them around?) and kick off new work based on those results, before you even get the result back.
This is far far far superior to everything else, totally different ball-game.
I've been a little rebuffed by wasm when I try, keep getting too close to some gravitational event horizon & get sucked in & give up, but for more data-throughput oriented systems, I'm still hoping wrpc ends up being a fantastic pick. https://github.com/bytecodealliance/wrpc . Also Apache Arrow Flight, which I know less about, has mad traction in serious data-throughput systems, which being adjacent to amazingly popular Apache Arrow makes sense. https://arrow.apache.org/docs/format/Flight.html
Maybe I'm missing some additional features but that's exactly what https://buf.build/plugins/typescript does for Protobuf already, with the advantage that you can just keep Protobuf and all the battle hardened tooling that comes with it.
In the "dense JSON" format, isn't representing removed/absent struct fields with `0` and not `null` backwards incompatible?
If you remove or are unaware of a `int32?` field, old consumers will suddenly think the value is present as a "default" value rather than absent
``` struct User { id: int64; email: string?; name: string; } ```
You store some users in a database: [10,"john@gmail.com""john"], [11,"jane",null,"john@gmail.com"]
You remove the email field later:
``` struct User { id: int64; name: string; removed; } ```
Supposedly you remove a field after you have migrated all code that uses the field and you have deployed all binaries.
In your DB, you still have [10,john@gmail.com","john"], [11,null,"jane"], which you are able to deserialize fine (the email field is ignored). New values that you serialize are stored as [12,0,"jack"]. If you happen to have old binaries which still use the old email field and which are still running (which you shouldn't, but let's imagine you accidentally didn't deploy all your binaries before you removed the field), these new binaries will indeed decode the email field for new values (Jack) as an empty string instead of null.
The best thing Skir does is strict generated constructors. You add a field, every construction site lights up. Protobuf's "silently default everything" model has caused mass production incidents at real companies. This is a legitimately better default.
Dense JSON is interesting but the docs gloss over the tradeoff: your serialized data is [3, 4, "P"]. If you ever lose your schema, or a human needs to read a payload in a log, you're staring at unlabeled arrays. Protobuf binary has the same problem but nobody markets binary as "easy to inspect with standard tools." The "serialize now, deserialize in 100 years" claim has a real asterisk. Compatibility checking requires you to opt into stable record IDs and maintain snapshots. If you skip that (and the docs' own examples often do), the CLI literally warns you: "breaking changes cannot be detected." So it's less "built-in safety" and more "safety available if you follow the discipline." Which is... also what Protobuf offers.
The Rust-style enum unification is genuinely cleaner than Protobuf's enum/oneof split. No notes there, that's just better language design.
Minor thing that bothered me disproportionately: the constant syntax in the docs (x = 600) doesn't match what the parser actually accepts (x: 600).
The weirdest thing that bugged the heck out of me was the tagline, "like protos but better", that's doing the project no favors.
I think this would land better if it were positioned as "Protobuf, but fresh" rather than "Protobuf, but better." The interesting conversation is which opinions are right, not whether one tool is universally superior.
Quite frankly, I don't use protobuf because it seems like an unapproachable monolith, and I'm not at FAANG anymore, just a solo dev. No one's gonna complain if I don't. But I do love the idea of something simpler thats easy to wrap my mind around.
That's why "but fresh" hits nice to me, and I have a feeling it might be more appealing than you'd think - ex. it's hard to believe a 2 month old project is strictly better than whatever mess and history protobufs gone through with tons of engineers paid to use and work on it. It is easy to believe it covers 99% of what Protobuf does already, and any crazy edge cases that pop up (they always do, eventually :), will be easy to understand and fix.
You’re a better man than me. If the docs can’t even get the syntax right, that’s a hard no from me.
Also, fwiw, you’ve got a few points wrong about protos. Inspecting the binary data is hard, but the tag numbers are present. You need the schema, but at least you can identify each element.
Also, I disagree on the constructor front. Proto forces you to grapple with the reality that a field may be missing. In a production system, when adding a new field, there will be a point where that field isn’t present on only one side of the network call. The compiler isn’t saving you.
Fresh is more honest than better, and personally, I wouldn’t change it.
I agree it's important for users to understand that newer fields won't be set when they deserialize old data -- whether that's with Protobuf or Skir. I disagree with the idea that not forcing you to update all constructor call sites when you add a field will help (significantly) with that. Are you saying that because Protobuf forces you to manually search for all call sites when you add a field, it forces you to think about what happens if the field is not set at deserialization, hence, it's a good thing? I'm not sure that outweighs the cost of bugs introduced by cases where you forget to update a constructor call site when you add a field to your schema.
Some callers may not need to update right away, or don’t need the new feature at all, and breaking the existing callers compilation is bad. If your caller is a different team, for example, and their CICD breaks because you added a field, that’s bad. Each place it’s used, you should think about how it’ll be handled, BUT ALSO, your system explicitly should gracefully handle the case where it’s not uniformly present. It’s an explicit goal of protos to support the use case where heterogeneous schema versions are used over the wire.
If a bug is introduced because the caller and handler use different versions, the compiler wasn’t going to save you anyways. That bug would have shown up when you deploy or update the client and server anyways - unless you atomically update both at once. You generally cannot guarantee that a client won’t use an outdated version of the schema, and if things break because of that, you didn’t guard it correctly. That’s a business logic failure not a compilation failure.
For dense JSON: the idea is that it is often a good "default" choice because it offers a good tradeoff across 3 properties: efficiency (where it's between binary and readable JSON), persistability (safe to evolve shema without losing backward compatibility), and readability (it's low for the reasons you mentioned, but it's not as bad as a binary string). I tried to explain this tradeoff in this table: https://skir.build/docs/serialization#serialization-formats
I hear your point about the tagline "like protos but better" which I hesitated to put because it sounds presumptuous. But I am not quite sure what idea you mean to convey by "fresh"?
GH style import. This is a big one I wish proto had in the first place. The entire idea of a proto registry feels reactive to me when, ideally, you want to pull in a versioned shared file to import that is verified by the compiler long before serve or client verifies the payload schema.
Schema validation and compatibility checks on CI. Again a big one and critical to catch issues early.
Enums done right... No further comment required.
I think with some more attention to details e.g. hammering out the gaps some other comments have identified and more language support e.g. Rust, Go, C# this can actually work out over time.
Here is an idea to contemplate as a side gig with your favorite Ai assistant: A tool to convert proto to Skir. Or at least as much as possible. As someone who had to maintain larger and complex proto files, a lot of proto specific pain points are addressed.
The only concern i have is timing. Ten years ago this would have been a smash hit. These days, we have Thrift and similar meaning the bar is definitely higher. That's not necessarily bad, but one needs to be mindful about differentiation to the existing proto alternatives.
I hope this project gains trajectory and community especially from the frustrated proto folks.
I completely agree with you about timing, wish I had done this 10 years ago :)
"Here is an idea to contemplate as a side gig with your favorite Ai assistant: A tool to convert proto to Skir. Or at least as much as possible. As someone who had to maintain larger and complex proto files, a lot of proto specific pain points are addressed." < I tried asking Claude: "Migrate this project from protobuf to Skir, see https://skir.build/" and it works pretty well. I created http://skir.build/llms.txt which helps with this. The pain point is data migration though, and as much as I want Skir to succeed: I cannot recommend people migrating from protobuf to Skir if they have some persisted data to migrate, the effort is probably not worth it.
protobuf solved serialization with schema evolution back/forward compatibility.
Skir seems to have great devex for the codegen part, but that's the least interesting aspect of protobufs. I don't see how the serialization this proposes fixes it without the numerical tagging equivalent.
The implicit version is brittle design for backwards compatibility.
People/LLMs will keep adding fields out of order and whatever has been serialised (both in client/server interaction, and stored in dbs) will be broken.
1. Google uses protobufs everywhere, so having something that behaves equivalently is very valuable. For example in protobuf renaming fields is safe, so if they used field names in the JSON it would be protobuf incompatible.
2. It is usually more efficient because you don't send field names. (Unless the struct is very sparse it is probably smaller on the wire, serialized JS usage may be harder to evaluate since JS engines are probably more optimized for structs than heterogeneous arrays).
3. Presumably the ability to use the native JSON parsing is beneficial over a binary parser in many cases (smaller code size and probably faster until the code gets very hot and JITed).
Consider numeric types -
JSON: number aka 64-bit IEEE 754 floating point
Proto: signed and unsigned int 8, 16, 32, 64-bit, float, double
I can only imagine the carnage saved by not accidentally chopping of the top 10 bits (or something similar) of every int64 identifier when it happens to get processed by a perfectly normal, standards compliant JSON processor.
It's true that most int64 fields could be just fine with int54. It's also true that some fields actually use those bits in practice.
Also, the JSPB format references tag numbers rather than field names. It's not really readable. For TextProto it might be a log output, or a config file, or a test, which are all have ways of catching field name discrepancies (or it doesn't matter). For the primary transport layer to the browser, the field name isn't a forward compatible/safe way to reference the schema.
So oddly the engineers complaining about the multiple text formats are also saved from a fair number of bugs by being forced to use tools more suited to their specific situation.
I like constants, great addition.
Things that I'll miss:
1. Oneof fields. There are enums, but it looks like it's not possible to have ad-hoc onefos?
2. Streaming requests/responses.
3. Introspection and annotations.
4. Go bindings.
1. You can create an enum with just "wrapper" fields, that's exactly like a oneof
2. Totally fair, I'm planning to work on this later this year, probably Q3 (priority is adding support to 4 more languages, and then I'll get to it)
3. So there is introspection in the 6 targeted languages, and I think I did it a bit better than protobuf because it generally has better type safety. Example in C++: https://github.com/gepheum/skir-cc-example/blob/main/string_...;
Typescript: https://skir.build/docs/typescript#reflection
I realize I haven't documented it in Python (although it is available and generally the same API as Typescript), will fix that
However, you're right that there is no support yet for annotations. Still trying to gauge whether that's needed
4. Assuming you mean Go language: working on that now, hoping to have C#, Go, Rust and Swift in the next 2-3 months.
A bit different kind of introspection. In Protobuf I can write a code generator that loads the compiled PB descriptions and then generates whatever it needs.
For example, I'm using it to generate SQL-serializing wrappers for my Protobuf types for Go.
Oh yeah, also having a standardized pretty-printer would be great.
As per messagepack, jsonbinpack, these seem to be layers on top of JSON to make JSON more compact. They still use field names for field identity, which I think can be problematic for long-term data persistence since it prevents renaming fields. I think the Protobuf/Thrift approach of using meaningless field numbers in serialization forms is better.
Little-understood fact about Cap'n Proto: Serialization is not the game at all. The RPC system is the whole game, the serialization was just done as a sort of stunt. Indeed, unless you are mmap()ing huge files, the serialization speed doesn't really matter. Though I would say the implementation of Cap'n Proto is quite a bit simpler than Protobuf due to the serialization format just being simpler, and that in itself is a nice benefit.
The recently-released Cap'n Web jettisons the whole serialization side and focuses just on the RPC system: https://blog.cloudflare.com/capnweb-javascript-rpc-library/
(I'm the author of Cap'n Proto and Cap'n Web.)
Unfortunately, I really like postfix types, but IDL itself doesn't support them.
Why build another language instead of extending an existing one?
I think the Protobuf language (which Skir is heavily influenced by) has some flaws in its core design, e.g. the enum/oneof mess, the fact that it allows spare field numbers which makes the "dense JSON" format (core feature of Skir) harder to get, the fact that it does not allow users to optionally specify a stable identifier to a message to get compatibility checks to work.
I get your point about "why building another language", but also that point taken too far means that we would all be programming in Haskell.