Bump to uniffi-rs 0.3.0

[jhugman]

This is a tracking issue. Many issues should be created and fixed in their own separate PRs.

Before we do this, we should do a final 0.29.x release.

Here is the changelog for uniffi-rs:

• Enums and Records support exporting uniffi traits (ie, Display, Hash, Eq etc) Support "standard rust traits" for enums and records? mozilla/uniffi-rs#2555
• Support for exporting the Ord trait, allowing objects to be ordered by Rust Allow objects to export the Ord trait. mozilla/uniffi-rs#2583.
• #[uniffi(default)] literals are now optional - eg, #[uniffi(default)] and #[uniffi(default = 0)] are equivalent. Similarly for args; #[uniffi::export(default(arg_name))]. When no literal is specifed, named types (objects, records, etc) can be used as long as they have suitable default values. Proc-macros allow default values without needing to specify a literal. mozilla/uniffi-rs#2543. Custom types too Support default value for custom type mozilla/uniffi-rs#2603
• Custom enum and object types can be used as error type Support Type::Custom{ builtin: Enum|Object, .. } as throws type mozilla/uniffi-rs#2658
• Objects can implement external traits Can't declare an object implements a trait which is defined externally. mozilla/uniffi-rs#2430

Breaking changes

• uniffi_bindgen::backend has been removed.
• #[uniffi(default)] changes how defaults are represented.
• FfiType::RustArcPtr has been removed and the FFI type for objects/interfaces is now a u64. Bindings authors will need to update their code to reflect this:
  • Lowering/lifting now uses u64 values
  • The free function inputs a u64 handle rather than a raw pointer
  • The clone function inputs and returns a u64 handle rather than a raw pointer
• Enums and Records can have methods, so the Method now carries self_type instead of the object name. In the templates, for Callable.takes_self() is replaced with Callable.self_type().
• Trait / Callback interface changes
• VTable fields are now: free, clone, followed by a field for each interface method. Note That free is now at the start of the vtable rather than the end.
  • Trait interface changes:
    • Foreign handles must always have the lowest bit set
    • Both Rust and foreign handles can now be passed across the FFI. When Lifting/lowering trait interface handles, check if the handle was generated from Rust or the foreign side.
  • See https://github.com/mozilla/uniffi-rs/pulls/2586 examples of how the builtin bindings here changed.

[ladvoc]

Hi @jhugman, I am currently working on UniFFI adoption in my organization, and I would like to contribute to this project. If there's anything I can do to help, please let me know.