starlark-rust VS json5

I haven't seen anyone mention starlark yet. It's something I want to play with as a config language.

Aside from these, if you want some inspiration for a production-grade language built in Rust, you might want to go through the source code of Starlark and Gluon.

There is also a Rust implementation of Starlark as a starting point https://github.com/facebookexperimental/starlark-rust

To add to everyone else, please don't use YAML. Starlark is great _precisely_ because it is a readable, well known (nearly Python) language that is limited at the same time (no unbounded for loops, no way to do non-deterministic things like get the current time or `random()`).

This is a follow-up to Benchmarking mlua/rlua/rhai - Rust embedded scripting languages from 4mo ago; I just added the new Starlark implementation from Meta to the benchmark posted by @aleksru.

The Rust implementation has it as an experimental extension (https://github.com/facebookexperimental/starlark-rust/blob/m...)

u/ndmitchell has been working on a Starlark interpreter. He wrote up a blog post with some thoughts about different interpreter styles. He found that in his case using fixed sized instructions was about the same as byte-encoded ones, but compiling the AST to closures was also about the same performance as well, and doesn't need an AST->bytecode compiler.

As mentioned in other comments, type system features like algebraic data types (that Rust has) are really helpful. If you want a small-but-real example of a compiler in Rust (with an optimizer etc) then the starlark-rust compiler is good.

If your Rust program needs a more complicated configuration (conditionals, access to APIs and so on), also look at Facebook's Starlark parser and tooling[1]. Starlark is a subset of Python used by Bazel, Buck and a few other projects.

[1]: https://github.com/facebookexperimental/starlark-rust

The Facebook post gives a nice overview. It also links out to the home page for the project at https://github.com/facebookexperimental/starlark-rust/, which has an introduction and links to what Starlark is, the crates.io link, the docs.rs link etc.

JSON5 support

Meanwhile, formats have been evolving (JSON5, YAML), config entry points are constantly changing. These fluctuations, fortunately, were covered by tools like the cosmiconfig.

I think JSON5 is fairly close to this: https://json5.org

I reckon the only thing it's missing to be truly accessible to non-techies is that string values still need to be quoted, i.e. you can't have:

key: this is my value

(I'm definitely not saying it would be a good idea to allow quotes to be dropped, just that that's the only potential stumbling block I see for non-techies.)

I believe that's JSON5.

https://github.com/json5/json5

It's my preferred configuration file format, it fixes all the problems I have with JSON (trailing commas, comments) without turning it into a mess full of gotchas like YAML.

JSON 5 support

I would like to see mention of JSON5 which is 11 years its elder. For comments in JSON, JSON5 is a good starting point.