Rust: How to Fix wit_bindgen's 'package not found' Error for Same-Directory WIT Files?

[NicFTK]

When the wit_bindgen::generate! macro runs, it fails to find the package local:val defined in val.wit and reports an error like "package 'local:val' not found" (or with a version, e.g., local:val@1.0.0).

Relevant Code Structure:

assets/wit/val.wit

(defines common types and declares the package local:val)

  package local:val@1.0.0; 
  interface types {

    variant val {
        null,
        blob(blob),
        boolen(bool),
        str(string),
        float(f64),
        int(s64),
        error(string),
    }
}

// 可能还有 world 定义，但接口是关键
world val {
  export types;
}

assets/wit/acme-plugins.wit

(uses types from val.wit via use local:val.{...})

// filepath: assets/wit/acme-plugins.wit
package acme:plugins@1.0.0;

interface host {
    log: func(message: string);
}

interface prettify-plugin {
    use local:val/types@1.0.0.{val}; 
    prettify: func(content: string) -> val; 
}

world prettify {
    import host;
    export prettify-plugin;
}

crates/plugin/src/bindings.rs

(calls wit_bindgen::generate!)

use crate::val::exports::local::val;

wit_bindgen::generate!({
    path: "../../assets/wit/acme-plugins.wit", // Points to the main WIT file
    default_bindings_module: "crate::bindings",
    pub_export_macro: true,
    // I tried adding 'with' or 'dependencies', but neither seems correct or recognized
    // with: {
    //    "local:val/types@1.0.0": crate::val::exports::local::val::types // Appears to map already generated types rather than help with discovery
    // }
});

error message

package 'local:val@1.0.0' not found. known packages:
    acme:plugins@1.0.0
     --> \\?\G:\Aduit_Project\Rust_Test_Demo\rust-wasm-plugins-examples\assets\wit\acme-plugins.wit:20:9
      |
   20 |     use local:val/types@1.0.0.{val};
      |         ^--------rustc[Click for full compiler diagnostic](rust-analyzer-diagnostics-view:/diagnostic%20message%20%5B0%5D?0#file%3A%2F%2F%2Fg%253A%2FAduit_Project%2FRust_Test_Demo%2Frust-wasm-plugins-examples%2Fcrates%2Fplugin%2Fsrc%2Fbindings.rs)

Expected Behavior:

I expect wit_bindgen::generate! to automatically resolve dependencies like local:val by searching the directory of the main WIT file (acme-plugins.wit, located at ../../assets/wit/), as long as val.wit exists in the same directory and properly declares its package.

Questions:

Should wit_bindgen::generate! automatically handle WIT dependencies in the same directory?

If yes, what configuration or file structure might I be missing?

If not, how should I configure wit_bindgen::generate! or restructure the project to ensure it finds and uses val.wit?

[alexcrichton]

I've written up some documentation here (I should have done this awhile ago...)

The problem is that when you specify a single file for bindings generation then that's all that's read from the filesystem. If the dependency is located in another file then you either need to (a) use the directory format for WIT instead, (b) specify the packages in a single file with inline package annotations, or (c) specify path: [ ... ] with the two files.

[NicFTK]

Thank you very much. Now it works for me with the following configuration:

wit_bindgen::generate!({
    path: ["../../assets/wit/val.wit","../../assets/wit/acme-plugins.wit",],
    default_bindings_module: "crate::bindings",
    pub_export_macro: true,
    generate_all,
});

[NicFTK]

Now I want to try using the [with] into its own crate and implement some common methods for it, so that I can reuse these types in the future. Therefore, I want to use to replace the existing bindings, but I encountered an error: package 'local:val@1.0.0' not found. known packages:
wit_bindgen::generate!({

    path:  "../../assets/wit/acme-plugins.wit",
    default_bindings_module: "crate::bindings",
    pub_export_macro: true,
    with: {
        "local:val@1.0.0": crate::val::exports::local::val,
    }
});

I searched some documentation but did not find a similar issue. Am I using it incorrectly somewhere?

[alexcrichton]

The error message highlights path: "..." which is different from the invocation that you said worked, which was using path: [...], are you sure that the path there is correct? The error message looks like it's about WIT discovery/parsing, unrelated to with.

[NicFTK]

Initially, I assumed that using with would directly replace the modules in WIT with the ones specified in the with configuration, without continuing to search for existing WIT files. After modifying my code as shown below

wit_bindgen::generate!({

    world:"acme:plugins/prettify",
    path: ["../../assets/wit/val.wit","../../assets/wit/acme-plugins.wit",],

    default_bindings_module: "crate::bindings",
    pub_export_macro: true,
    with: {
        "local:val/types@1.0.0": crate::val::exports::local::val::types, 
    }
});

the error has been resolved. I will test my code further to ensure everything works as expected before closing this issue. Additionally, I plan to document the issues I encountered and their solutions to serve as a reference for other beginners. Thank you for your patience and support!

[alexcrichton]

Sounds good, and thanks! Docs are always welcome :)

And yeah WIT resolution happens at a different layer than with, the WIT resolution all happens in isolation and with only affects the generated bindings after the WIT was parsed.

[NicFTK]

Finally I have some free time to finish my demo. I had no issues so far when working with wit-bindgen, but I ran into a problem binding the same WIT to Wasmtime. The main issue is that I want to reuse the structs defined in the [val] module, but right now I’m not sure how to proceed to fix the error.

here is my test project
https://github.com/NicFTK/Rust_Wasm_Plugin_Example