How to Convert JSON Back to AST Tree in Rust?

[shahryarjb]

Hello friends. Sorry, I’m new to Rust. Recently, I’ve been working on this project, and I’m facing an issue. I can’t convert an AST structure that I’ve transformed into JSON back into a tree.

For example, consider the following code:

let js_code = r#"
    function calculateWeight(value1, value2) {
        const product = value1 * value2;
        return `Your weight is ${product} kg.`;
    }
"#;
let parse_result = parse_script(js_code, JsParserOptions::default());
let json_string = serde_json::to_string_pretty(&parse_result.tree()).unwrap();
println!("Generated JSON:\n{}", json_string);

Now, how can I convert the json_string back into its original tree structure?

Why do I need this?

I want to transform a JavaScript code snippet into an AST, then convert the AST to JSON and send it to Elixir. After making the necessary modifications in Elixir, I want to send the JSON back to Rust, where I can convert it back into a tree to review the changes and handle other required tasks.

I tried using deserialize_from_json_str, but I encountered many errors.

Thank you for your help!

[ematipico]

You simply can't because our nodes don't implement the Deserialize trait from serde.

[shahryarjb]

Hi @ematipico ,
Thank you for your response and the time you spent. I just have one question: Is it entirely impossible to convert to JSON and back to Rust for Biome, or is it because I used serde for the Tree that this isn’t possible?

Is there anything specifically supported by Biome for this?

Thank you again, and sorry for taking up your time.

[ematipico]

We simply never had a use case where someone wants to create an AST from its JSON representation. You're essentially describing a parsing phase, somehow :)

I understand what you want to do, but I still fail to see the final use case

[shahryarjb]

Thank you @ematipico (Just to clarify, I hope I haven’t caused any inconvenience. 😊).
I wanted to completely port your library to the Elixir language and build a wrapper for it. Using the Rustler library, only a limited number of types can be prepared for Elixir, and communication between them happens in Erlang (Nif). From my perspective, the best way to transfer data was to convert it to JSON.

However, I might be mistaken due to my limited knowledge of Rust. But considering the large number of types involved...
If I could transfer the AST to Elixir and use some of your library’s functions, I would be able to enable users in Elixir to safely modify their JS and CSS files, for example, when building a CLI tool.

Thank you again!

[arendjr]

I have a tiny bit of experience with Rustler, and I think you’re right: converting to JSON is probably your best bet.

The problem is that deserializing (whether it’s from JSON or something else) is quite a complex operation, given the data structures involved, and is indeed almost as difficult as implementing a custom parser, minus the syntax bits.

So you understand why we haven’t implemented this :)

[shahryarjb]

Thank you and the other maintainers of this project for all your efforts. I understand, and I was just hoping there might be a way for it.