@since gates should not transitively apply across package boundaries when worlds are included

[ydnar]

Extending from #306, WIT version gates cannot be correctly represented in the fully-resolved representation of a component, e.g. in JSON.

The problem arises when a world in package A includes a world from package B, which imports or exports an interface with a version gate, e.g. @since(version = 0.2.0). The fully-resolved version of the component as emitted from wasm-tools will include the package B version gate in the world inside package A.

Testdata

wit-bindgen-go uses [email protected] internally to parse the WIT, produce a Resolve, and serialize to JSON, which is then loaded and then re-serialized into WIT.

The existing test corpus in this repo performs a WIT → JSON → WIT round trip verification for every JSON file in testdata. This is currently breaking for 2 files (issues/issue325.wit and wit-parser/gated-include-use-with-stable.wit). See #326 for more information.

Links:

1. https://github.com/WebAssembly/component-model/blob/main/design/mvp/WIT.md#feature-gates
2. fix mismatch in stability attributes error in wit-parser wasm-tools#2076

cc @alexcrichton @Mossaka

[ydnar]

The following WIT demonstrates the issue:

package issues:issue325;

world w {
	@unstable(feature = active)
	include issues:dep1/w@0.1.0;
	include issues:unstable/w@0.1.0;
}

package issues:unstable@0.1.0 {
	world w {
		@unstable(feature = active)
		use issues:dep2/[email protected].{r};
	}
}

package issues:dep1@0.1.0 {
	world w {
		include issues:dep2/[email protected];
	}
}

package issues:dep2@0.2.0 {
	world w {
		@since(version = 0.2.0)
		import i;
	}

	interface i {
		resource r;
	}
}

Result when processed through a version of wit-bindgen-go that strips incompatible @since gates, with wit-bindgen-go wit:

package issues:issue325;

world w {
	import issues:dep2/i@0.2.0;
	@unstable(feature = active)
	use issues:dep2/i@0.2.0.{r};
}

package issues:dep1@0.1.0 {
	world w {
		import issues:dep2/[email protected];
	}
}

package issues:unstable@0.1.0 {
	world w {
		@unstable(feature = active)
		import issues:dep2/[email protected];
		@unstable(feature = active)
		use issues:dep2/[email protected].{r};
	}
}

package issues:dep2@0.2.0 {
	interface i {
		resource r;
	}

	world w {
		@since(version = 0.2.0)
		import i;
	}
}

When the above is processed through wit-bindgen-go wit, the output changes:

package issues:issue325;

world w {
	@unstable(feature = active)
	import issues:dep2/i@0.2.0;
	@unstable(feature = active)
	use issues:dep2/i@0.2.0.{r};
}

package issues:dep1@0.1.0 {
	world w {
		import issues:dep2/[email protected];
	}
}

package issues:unstable@0.1.0 {
	world w {
		@unstable(feature = active)
		import issues:dep2/[email protected];
		@unstable(feature = active)
		use issues:dep2/[email protected].{r};
	}
}

package issues:dep2@0.2.0 {
	interface i {
		resource r;
	}

	world w {
		@since(version = 0.2.0)
		import i;
	}
}

[alexcrichton]

I wrote up some more thoughts here but tl;dr; I think this is a bug in wasm-tools to fix.