Get typed AST from Rescript file

1

I believe I want to do the reverse of How do I extract the rescript AST?

I have a Rescript file and I want to inspect the (typed) AST of a file.
How can I do this? I don’t really know any ocaml, so if I can just dump something to json that would be ideal. But if that is not possible, some ocaml pointers would do as well.

2

Getting the typed AST isn’t possible without OCaml, but there are some loose plans to expose a subset of the relevant parts of the typed AST as JSON via the @rescript/tools package.

A hack, but what you can try today is running the doc command from @rescript/tools on your file: rescript-vscode/tools/README.md at master · rescript-lang/rescript-vscode · GitHub

That will dump out JSON using the typed AST for that file. It’s intended for driving doc generation, but you might find what you need in there already.

3

Thanks! That would be something like npx rescript-tools doc src/CreateOrder.res right?
This isn’t doing anything right now, so I probably missing something?

4

I installed sudo apt install musl and this started working.
That json does (more or less) contain what I need.
Thanks a bunch @zth!

5

Related shower thought: maybe producing some web assembly binary (assuming that is easy in OCAML) that exposes this could be an interesting route to explore.

6

Which part, for dumping out info?

Btw, did you manage to do anything with the docs json?

7

Btw: how does the decoder output look like (RescriptTools.Docgen.decodeFromJson)?

8

There’s no decoder, it’s just an identity function. The full structure can be modelled using v11 variants (which is an achievement in itself!).

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9

Oh okay. Didn’t look into the code. Just saw the last code block in the README.

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10

Let’s see if I can find some time to get an initial experimental version out where we can dump typed info to JSON, and we can build on it from there. Easy access to a structured way of working with type info in not just OCaml can hopefully enable some cool innovation.

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11

Yes, for getting AST information.
I was able to solve my use case with the JSON documentation dump.
I needed the exported function names and their input and return type, which I was able to find in the JSON.

12

Couldn’t we generate a json schema of rescript AST? Then one could use pretty much any tool to work on it, including rescript using rescript-json-schema for example.

13

There is btw some more interest in this from the compiler discussions: How can I get AST/CST of a rescript file in JSON format? · rescript-lang/rescript-compiler · Discussion #6622 · GitHub