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Previously, all Wiggle-generated traits were generated with `&mut self` signatures. With the addition of the `mutable` configuration option to `from_witx!` and `wasmtime_integration!`, one can disable this, emitting instead traits that use `&self` (i.e., `mutable: false`). This change is helpful for implementing wasi-threads: WASI implementations with interior mutability will now be able to communitcate this to their Wiggle-generated code. The other side of this change is the `get_cx` closure passed to Wiggle's generated `add_to_linker` function. When `mutability` is set to `true` (default), the `get_cx` function takes a `&mut` data structure from the store and returns a corresponding `&mut` reference, usually to a field of the passed-in structure. When `mutability: false`, the `get_cx` closure will still take a `&mut` data structure but now will return a `&` reference.
wiggle
Wiggle is a code generator for the host side of a witx interface. It is
invoked as a Rust procedural macro.
Wiggle is not specialized to any particular WebAssembly runtime. It is usable in at least Wasmtime and Lucet.
Learning more
Read the docs on docs.rs.
There are child crates for integrating with Wasmtime and Lucet.
The wasi-common crate is implemented using Wiggle and the wasmtime-wasi crate integrates wasi-common with the Wasmtime engine.
Andrew Brown wrote a great blog post on using Wiggle with Wasmtime.