✔ rules for wasi imports? · cargo-component

Trying to understand this. If I build a new component following the rust component docs cargo component new --reactor add, then I extract the .wit file from the generated wasm, I see a very simple:

package root:component;

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

But if I now change the component to return a string rather than an s32, then I build the component with a new wit file:

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

extracting the .wit file from the resulting components shows a new interface that includes all wasi imports:

package root:component;

world root {
  import wasi:cli/environment@0.2.0-rc-2023-12-05;
  import wasi:cli/exit@0.2.0-rc-2023-12-05;
  import wasi:io/error@0.2.0-rc-2023-11-10;
  import wasi:io/streams@0.2.0-rc-2023-11-10;
  import wasi:cli/stdin@0.2.0-rc-2023-12-05;
  import wasi:cli/stdout@0.2.0-rc-2023-12-05;
  import wasi:cli/stderr@0.2.0-rc-2023-12-05;
  import wasi:clocks/wall-clock@0.2.0-rc-2023-11-10;
  import wasi:filesystem/types@0.2.0-rc-2023-11-10;
  import wasi:filesystem/preopens@0.2.0-rc-2023-11-10;

  export add: func(x: s32, y: s32) -> string;
}

Peter Huene (Jan 03 2024 at 19:47):

My guess would be that the bindings generated to marshal the string pull in the panic infrastructure from the Rust standard library, which will call the WASI preview1 versions of things like getting environment variables, printing to the console, and exiting. cargo-component will automatically adapt the stdlib's preview1 calls to preview2

Stream: cargo-component

Topic: ✔ rules for wasi imports?

James Mart (Jan 03 2024 at 19:23):

Peter Huene (Jan 03 2024 at 19:47):

James Mart (Jan 03 2024 at 20:05):

Notification Bot (Jan 03 2024 at 20:05):