cbeb301371
* Shard the `convert.rs` module into sub-modules Hopefully this'll make the organization a little nicer over time! * Start adding support for optional types This commit starts adding support for optional types to wasm-bindgen as arguments/return values to functions. The strategy here is to add two new traits, `OptionIntoWasmAbi` and `OptionFromWasmAbi`. These two traits are used as a blanket impl to implement `IntoWasmAbi` and `FromWasmAbi` for `Option<T>`. Some consequences of this design: * It should be possible to ensure `Option<SomeForeignType>` implements to/from wasm traits. This is because the option-based traits can be implemented for foreign types. * A specialized implementation is possible for all types, so there's no need for `Option<T>` to introduce unnecessary overhead. * Two new traits is a bit unforutnate but I can't currently think of an alternative design that works for the above two constraints, although it doesn't mean one doesn't exist! * The error messages for "can't use this type here" is actually halfway decent because it says these new traits need to be implemented, which provides a good place to document and talk about what's going on here! * Nested references like `Option<&T>` can't implement `FromWasmAbi`. This means that you can't define a function in Rust which takes `Option<&str>`. It may be possible to do this one day but it'll likely require more trait trickery than I'm capable of right now. * Add support for optional slices This commit adds support for optional slice types, things like strings and arrays. The null representation of these has a pointer value of 0, which should never happen in normal Rust. Otherwise the various plumbing is done throughout the tooling to enable these types in all locations. * Fix `takeObject` on global sentinels These don't have a reference count as they're always expected to work, so avoid actually dropping a reference on them. * Remove some no longer needed bindings * Add support for optional anyref types This commit adds support for optional imported class types. Each type imported with `#[wasm_bindgen]` automatically implements the relevant traits and now supports `Option<Foo>` in various argument/return positions. * Fix building without the `std` feature * Actually fix the build... * Add support for optional types to WebIDL Closes #502
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Reference
The table below provides an overview of all the types that wasm-bindgen can send/receive across the wasm ABI boundary.
| Type | T parameter | &T parameter | &mut T parameter | T return value | Option<T> parameter | Option<T> return value |
|:---:|:---:|:---:|:---:|:---:|:---:|
| str | No | Yes | No | Yes | Yes | No |
| char | Yes | No | No | Yes | No | No |
| bool | Yes | No | No | Yes | No | No |
| JsValue | Yes | Yes | Yes | Yes | No | No |
| Box<[JsValue]> | Yes | No | No | Yes | Yes | yes |
| *const T | Yes | No | No | Yes | No | No |
| *mut T | Yes | No | No | Yes | No | No |
| u8 i8 u16 i16 u64 i64 isize size | Yes | No | No | Yes | No | No |
| u32 i32 f32 f64 | Yes | Yes | Yes | Yes | No | No |
| Box<[u8]> Box<[i8]> Box<[u16]> Box<[i16]> Box<[u32]> Box<[i32]> Box<[u64]> Box<[i64]> Box<[f32]> Box<[f64]> | Yes | No | No | Yes | Yes | Yes |
| [u8] [i8] [u16] [i16] [u32] [i32] [u64] [i64] [f32] [f64] | No | Yes | Yes | No | Yes | No |