Show HN: Zero-codegen, no-compile TypeScript type inference from Protobufs

[mubou]

The fact that the source is so small is wild. I would have expected a huge convoluted parsing library implemented in types.

On the other hand, the fact that this is even possible is more wild. Instead of replacing JS with a proper statically-typed language, we're spending all this effort turning a preprocessor's type system into a turing-complete metalanguage. Pretty soon we'll be able to compile TypeScript entirely using types.

[spankalee]

TypeScript does an amazing job at describing the types of real-world JavaScript. It's incredibly good, and very useful, even in the face of extremely dynamic programs. The fact that it can describe transforms of types, like "this is a utility that adds an `xxx` prefix to every property name" is frankly unparalleled in mainstream languages, but more importantly lets us describe patterns that come up in real-world JS programs - it's not fluff!

And luckily, the most complex of types are usually limited to and contained within library type definitions. They add a lot of value for the library users, who usually don't have to deal that that level of complexity.

[sgrove]

Or even run doom in TypeScript's type system!

[18nleung]

I would have written a shorter source, but I did not have the time.

[throwanem]

People have fussed the same of the C preprocessor, around the same time I and maybe you were born. (There's a pretty good chance I'm your parents' age, and nearly no chance you're the age of mine.)

[sandreas]

Here is Doom in TypeScript types: https://www.tomshardware.com/video-games/porting-doom-to-typ...

A fun read / Video...

[plopz]

I wish javascript had gone in the same direction as php with types.

[spankalee]

This would be even nicer if TypeScript added type inference for tagged template literals, like in this issue [1]. Then you could write:

    const schema = proto`
      syntax = "proto3";

      message Person { ... }
    `;

    type Person = typeof schema['Person'];

And you could get built-in schema validation with a sophisticated enough type definition for `proto`, nice syntax highlighting in many tools with a nested grammar.

We would love to see this feature in TypeScript to be able to have type-safe template in lit-html without an external tool.

The issue hasn't seen much activity lately, but it would be good to highlight this library as another use case.

[1]: https://github.com/microsoft/TypeScript/issues/33304

[jitl]

It’s pretty rad how flexible template literal types are, but I can’t imagine wanting this kind of shenanigans hanging out in a production app slowing down compile times. I prefer to define types in TypeScript and generate proto from that, since the TypeScript type system is so much more powerful than the Protobuf system. Types are much more composable in TS.

[h1fra]

Can you run Doom in a Typescript string template?

[tantalor]

What do you use to go from ts->pb?

[mherkender]

This is kinda why I hate advanced type systems, they slowly become their own language.

"No compile/no codegen" sounds nice until you get slow compile times because a type system is slow VM, the error messages are so confusing it's hard to tell what's going on, and there's no debugging tools.

[throwanem]

I love this, and I bet the compile errors it produces on malformed protobuf are wild.

[pragma_x]

What's kind of amazing is that Typescript's matching of strings through the type system converges on a first-class PEG in a few places (see string.ts). The rest of the library is really damn succinct for how much lifting it's doing.

My hat's off to the author - I attempted something like this for a toy regex engine and got nowhere fast. This is a much better illustration of what I thought _should_ be possible, but I couldn't quite wrap my head around the use of the ternary operator to resolve types.

[jillyboel]

Cool, but I assume not great for performance?

Probably better to just stick with codegen

[18nleung]

You're right that IDE/dev-time performance might be slower than using generated types since this relies on "dynamic" TypeScript inference rather than static codegen'd types.

That said, depending on how your codegen works and how you're using protos at runtime, this approach might actually be faster at runtime. Types are stripped at compile-time and there’s no generated class or constructor logic — in the compiled output, you're left with plain JS objects which potentially avoids the serialization or class overhead that some proto codegen tools introduce.

(FWIW, type inference in VSCode seemed reasonably fast with the toy examples I was playing with)

[dtech]

Assuming you mean compiler/editor performance then yes I assume this wrecks it. Shouldn't matter for runtime though.

[aappleby]

This is both hilarious and awesome. I think the Typescript devs are just showing off at this point. :D

[anjandutta]

This is super cool — love the zero-codegen approach. I’ve had to deal with codegen hell in monorepos where a tiny .proto change breaks half the pipeline. Curious how this handles more complex types like nested messages or oneof fields?

Also, been building something in a different space (LeetCode prep tool), but the idea of removing build steps for dev speed really resonates. Would love to see how this could plug into a lightweight frontend setup.

[recursive]

This requires the whole `.proto` declaration inline in source a string constant. I'm not holding my breath on "Import non-js content"[1] getting approved, so that means you still have to use another build dependency, or manually keep the .proto files synchronized across multiple sources truth. In that light, it's not clear when this would be a benefit over straight-forward code gen. Cool POC hack though.

[1]: https://github.com/microsoft/TypeScript/issues/42219

[catapart]

It's true that it's another dependency, but this is the entire contents of a file I drop into my project root called `raw-loader.d.ts`:

```

declare module '*?raw' { const rawFileContent: string export default rawFileContent }

```

Then, when I add the file to my types property array of my tsconfig's compilerOptions, I can import anything I want into a typescript file as a string, so long as I add "?raw" to the end of it. I use it to inject HTML and CSS into templates. No reason it couldn't be used to inject a .proto file's contents into the inline template.

Again, you're technically correct! But a "import non js content" feature is a pretty solveable problem in TS. Maybe not at the language level, but at the implementation level, at least.

[yencabulator]

Even then, no import support -> must preprocess the .proto anyway.

Might as well do code generation at that point, it'd even be debuggable.

[ZitchDog]

The problem is that TypeScript is terrible at codegen, there are no standard extension points like we have with javac and others. So we are forced to do these crazy hacks at the type level rather than just generating types as you would in other languages.

[cadamsdotcom]

That can be done with a `sed` call so it’s not a new dependency.

[mifydev]

This makes me wonder if this the way to do schema generation in Typescript. I’m working on Typeconf, and we have a separate step for translating Typespec schema to Typescript, it’ll be cool if we could just load typespec directly.

[meindnoch]

Looks like TypeScript envies Swift's compile times.

[catapart]

Very cool work!

Also, I hope you expected me to read that output in the same cadence as the Hooli focus groups, because that's exactly what I did.

[porridgeraisin]

Cool. Once the linked TS issue is resolved it will be able to resolve from files too which is great

[tim1994]

It's always impressive how far people can take TypeScript and even build parsers with it. But this is limited to inlined string literals and cannot read files (a TS limitation).

I wonder if the author has a use case in mind for this that I don't see. Like if you are only using TS, what's the point of protobuf? If you are exchanging data with programs written in other languages why avoid the protobuf tooling that you need anyway?

Maybe this is just a fun toy project to write a parser in TS?

[nikolayasdf123]

I wish there was other way around. infer binary encoding from native types