Tutorial don't work

[feelingsonice]

Following the first part of the tutorial described here in Rust and running cargo component build --release simply don't work:

warning: `add` (lib) generated 1 warning
    Finished `release` profile [optimized] target(s) in 0.13s
    Creating component target/wasm32-wasip1/release/add.wasm
error: failed to decode world from module

Caused by:
    0: module was not valid
    1: failed to find export of function `add`

Tried a few versions:

package example:component;

world example {
    export add: func(x: s32, y: s32) -> s32;
}

and

package component:example;

world example {
    export add: func(x: s32, y: s32) -> s32;
}

I'm guessing it's outdated?

[kate-goldenring]

Looks like the example implementation is missing the following line to export functions:
bindings::export!(Component with_types_in bindings);.

The complete example implementation should be:

#[allow(warnings)]
mod bindings;

use bindings::Guest;

struct Component;

impl Guest for Component {
    fn add(x: i32, y: i32) -> i32 {
        x + y
    }
}

bindings::export!(Component with_types_in bindings);

There is an incident with GitHub right now , but ill push an update to the docs once it is resolved. Thank you for pointing this out @feelingsonice

[feelingsonice]

@kate-goldenring the line bindings::export!(Component with_types_in bindings); wasn't added to the example FYI

[feelingsonice]

Something else I just noticed:

The tutorial mentions something about cargo component build automatically creating a package.metadata.component.target section in your Cargo.toml:

Because there's no .wit file, Cargo.toml doesn't contain a package.metadata.component.target section.

Edit Cargo.toml to tell cargo component about the new WIT file:

[package.metadata.component.target]
path = "wit"

(This entry is created automatically for library components but not for command components.)

But when I do cargo component new <name> --lib this isn't there. Maybe something's changed?

[kate-goldenring]

@kate-goldenring the line bindings::export!(Component with_types_in bindings); wasn't added to the example FYI

@feelingsonice I reduced the scope in the example to make it clear to update the implementation but keep the boiler plate code otherwise. I did this to improve maintainability rather than making it a copy and paste example.