Add support for optional slice types #507
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After this I hope to change the macro generation for imported types to also generate Into/From wasm abi implementations for |
alexcrichton
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I've updated to tweak this a bit, it now interprets both This means that when you pass |
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Urgh actually so after implementing more of this I don't believe this strategy will work. |
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Ok! I've taken a different approach now for how the underlying infrastructure works and I've also implemented automatic implementations for |
Hopefully this'll make the organization a little nicer over time!
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.
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.
These don't have a reference count as they're always expected to work, so avoid actually dropping a reference on them.
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.
src/convert/traits.rs
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| //! This is mostly an internal module, no stability guarantees are provided. Use | |||
| //! at your own risk. | |||
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Are we going to make this stuff part of the stable interface now?
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Nah I hope to still keep this as an internal implementation detail (these docs just moved to src/convert/mod.rs). I'm not sure how long we'll be able to pull this off but I figured we may as well try!
This commit adds support for optional slice types to wasm-bindgen, allowing these types to be used for exported and imported APIs. They currently map to
undefinedin JS forNonein Rust, andSomein Rust for other values in JS.