Rust: Error in bindings when using wasi:http

Example .wit:

interface add {
    add: func(x: u32, y: u32) -> u32;
}

world planner {
    export add;
    include wasi:http/proxy@0.2.3;
}

With lib.rs:

#[allow(warnings)]
mod bindings;

use bindings::exports::component::planner::add::Guest;

struct Component;

impl Guest for Component {
    fn add(x: u32, y: u32) -> u32 {
        x + y
    }
}

bindings::export!(Component with_types_in bindings);

I ran wkg wit fetch and here is my Cargo.toml:

[package.metadata.component.target.dependencies]
"wasi:cli" = { path = "wit/deps/wasi-cli-0.2.3" }
"wasi:clock" = { path = "wit/deps/wasi-clocks-0.2.3" }
"wasi:http" = { path = "wit/deps/wasi-http-0.2.3" }
"wasi:io" = { path = "wit/deps/wasi-io-0.2.3" }
"wasi:random" = { path = "wit/deps/wasi-random-0.2.3" }

I ran cargo component bindings

Then when I try to build, I get:

error[E0277]: the trait bound `Component: incoming_handler::Guest` is not satisfied
    --> components/planner/src/bindings.rs:8488:68
     |
8488 |                         $($path_to_types)*:: _export_handle_cabi::<$ty > (arg0, arg1) } }
     |                                                                    ^^^ the trait `incoming_handler::Guest` is not implemented for `Component`
     |
    ::: components/planner/src/lib.rs:16:1
     |
16   | bindings::export!(Component with_types_in bindings);
     | --------------------------------------------------- in this macro invocation
     |
help: this trait has no implementations, consider adding one
    --> components/planner/src/bindings.rs:8466:17
     |
8466 |                 pub trait Guest {
     |                 ^^^^^^^^^^^^^^^
note: required by a bound in `_export_handle_cabi`
    --> components/planner/src/bindings.rs:8451:54
     |
8451 |                 pub unsafe fn _export_handle_cabi<T: Guest>(arg0: i32, arg1: i32) {
     |                                                      ^^^^^ required by this bound in `_export_handle_cabi`
     = note: this error originates in the macro `bindings::exports::wasi::http::incoming_handler::__export_wasi_http_incoming_handler_0_2_3_cabi` which comes from the expansion of the macro `bindings::export` (in Nightly builds, run with -Z macro-backtrace for more info)

This is the related line in bindings:

                #[doc(hidden)]
                macro_rules! __export_wasi_http_incoming_handler_0_2_3_cabi {
                    ($ty:ident with_types_in $($path_to_types:tt)*) => {
                        const _ : () = { #[unsafe (export_name =
                        "wasi:http/incoming-handler@0.2.3#handle")] unsafe extern "C" fn
                        export_handle(arg0 : i32, arg1 : i32,) { unsafe {
                        $($path_to_types)*:: _export_handle_cabi::<$ty > (arg0, arg1) } }
                        };
                    };
                }

Any idea what I am doing wrong?

You are including wasi:http/proxy in your wit.

If you check the definition of that world in your deps folder, you'll see which interfaces are imported and exported by that world. You'll see that it also exports an interface called incoming-handler, so you can think of that include statement as also creating an export for that interface, and requiring you to do everything you did in your source code that you had to do for the add interface being exported.

Here are some lines you can add to your code that should get rid of your error .

use crate::bindings::exports::wasi::http::incoming_handler::Guest as HttpGuest;

impl HttpGuest for Component {
    fn handle(
        request: bindings::exports::wasi::http::incoming_handler::IncomingRequest,
        response_out: bindings::exports::wasi::http::incoming_handler::ResponseOutparam,
    ) -> () {
        
    }
}

Where I just added a barebones function that meets the type constraints required by the interface defined in the wit.

But also maybe you could share a bit about what you were intending to be able to do when including wasi:http/proxy? You might be able to get some of what you're looking for (types or functionality) via import and/or use statements, instead of an include, since include requires you to export all of the interfaces exported by the world you're including.

Oooh that makes sense!

My goal was to do an http request inside my add component.

Here is what I ended up doing and this builds fine:

world planner {
    export types;
    import wasi:http/types@0.2.3;
    import wasi:http/outgoing-handler@0.2.3;
}

@Almaju

Hey @Almaju I know it's been a while, but we're trying to improve the docs so that others get that they can import/use rather than include, and making it clear where it makes sense to use which.

Do you happen to remember how you ended up using include? Which piece of documentation suggested that it might be reasonable? Was it a code snippet?

I am not sure but I guess here: https://component-model.bytecodealliance.org/design/wit.html#including-other-worlds
and also reading at some .wit from the wasi interfaces.

Navigation Menu

Repository navigation

Rust: Error in bindings when using wasi:http #245

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Rust: Error in bindings when using wasi:http #245

Description

Activity

macovedj commented on Apr 13, 2025

Almaju commented on Apr 13, 2025

vados-cosmonic commented on Apr 23, 2025

Almaju commented on Apr 24, 2025

Metadata

Metadata

Assignees

Labels

Type

Projects

Milestone

Relationships

Development

Issue actions