anb (Nov 19 2025 at 17:56): anb (Nov 19 2025 at 17:56):Hi, I wonder if there's any docs about adding/removing members from enum/variant break binary compatibility? And if so, what's the best/safe way to change an existing enum?
Lann Martin (Nov 19 2025 at 18:23):I don't think there is any kind of variant subtyping currently implemented in the component model, so any changes to variant cases would be backward-incompatible. The only "safe" ways to migrate would be to create a new variant that is only used by new functions or by updating the package version to indicate the backward-incompatibility.
anb (Nov 19 2025 at 18:47):Thanks Lann, how about enum? Is it backed by integers? Any way to safely change it without breaking anything?
Lann Martin (Nov 19 2025 at 18:55):Same for enums and all other value types. The ABI does indeed use integers but components have self-describing interfaces that include most of what is specified in WIT; see the spec here: https://github.com/WebAssembly/component-model/blob/main/design/mvp/Binary.md#type-definitions
Lann Martin (Nov 19 2025 at 18:57):In the specific case of enum you can see that the binary type information includes <label> strings.
anb (Nov 19 2025 at 19:27):That feels like a pain :-/
Lann Martin (Nov 19 2025 at 21:06):There was a rough outline of subtyping prior to the 0.2 release but it was removed. You can see some discussion of why here: #wasi > `@since` gates on variant and enum members? @ 💬
Last updated: Dec 06 2025 at 07:03 UTC