rvolosatovs edited issue #7701:
Feature
Refs https://github.com/bytecodealliance/wasmtime/issues/7676 #7680 #7688
Suggestion is to implement theget_typed_func
param/return bounds (i.e.ComponentNamedList
,Lower
andLift
) onwasmtime::component::Val
, such that one could bind the lengths of params/results, while still (partially) using the "polymorphic" types.Benefit
This would get us one step closer to a more type-safe and possibly more efficient approach for invoking guest Wasm functions, for which WIT is not known at compile-time, i.e. no bindings exist.
This would allow "partial bounds" on the function signatures exported by the Wasm, e.g.:
(u32, wasmtime::component::Val, wasmtime::component::ResourceAny) -> (wasmtime::component::Resource<T>)
Could be a valid function type bound, where the type of the second parameter could only be determined at runtime, for example, by inspecting the WIT embedded in the Wasm component executed.
Implementation
It feels like most of the functionality already exists, just not the trait implementations:
https://github.com/bytecodealliance/wasmtime/blob/e6a9fa19a2609213ce87a4fed40ab102ba83fa29/crates/wasmtime/src/component/values.rs#L623-L913Alternatives
Developers could use e.g. Rust macros to generate an implementation of a polymorphic
Call
trait for all possible signatures of exported component functions, which would be a lot of hard-to-maitain work, otherwise they could use untypedfunc
directly
rvolosatovs edited issue #7701:
Feature
Refs https://github.com/bytecodealliance/wasmtime/issues/7676 #7680 #7688
Suggestion is to implement theget_typed_func
param/return bounds (i.e.Lower
andLift
) onwasmtime::component::Val
, such that one could bind the lengths of params/results, while still (partially) using the "polymorphic" types.Benefit
This would get us one step closer to a more type-safe and possibly more efficient approach for invoking guest Wasm functions, for which WIT is not known at compile-time, i.e. no bindings exist.
This would allow "partial bounds" on the function signatures exported by the Wasm, e.g.:
(u32, wasmtime::component::Val, wasmtime::component::ResourceAny) -> (wasmtime::component::Resource<T>)
Could be a valid function type bound, where the type of the second parameter could only be determined at runtime, for example, by inspecting the WIT embedded in the Wasm component executed.
Implementation
It feels like most of the functionality already exists, just not the trait implementations:
https://github.com/bytecodealliance/wasmtime/blob/e6a9fa19a2609213ce87a4fed40ab102ba83fa29/crates/wasmtime/src/component/values.rs#L623-L913Alternatives
Developers could use e.g. Rust macros to generate an implementation of a polymorphic
Call
trait for all possible signatures of exported component functions, which would be a lot of hard-to-maitain work, otherwise they could use untypedfunc
directly
alexcrichton commented on issue #7701:
I originally didn't implement this because
Lift
andLower
inherit fromComponentType
which didn't have a way to type-check since&self
wasn't taken in thetypecheck
method. That being said nowadays the type is passed throughLift::lift
andLower::lower
so this should actually be possible to do nowadays by returning "true" from any call totypecheck
and then performing the actual type check at runtime in thelift
andlower
methods.I think this'd be a great idea to implement as well, thanks for filing an issue!
alexcrichton added the wasm-proposal:component-model label to Issue #7701.
Last updated: Dec 23 2024 at 12:05 UTC