v0.32.0

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⚠️ Breaking Changes ⚠️

• Kotlin and Python now fail to generate bindings when there are async primary constructors.
  Previously these languages skipped the constructor in this case or generated a constructor that always threw.
  You can get similar behavior by adding the primary constructor to the uniffi.toml excludes list in uniffi.toml (e.g. `excludes = ["MyObject.new"])
• Ruby: Force named parameters for enum constructors (#​2880)
• The --config flag now expects a global config file
  rather than a flat uniffi.toml-style override. Old-style files will produce a warning and be ignored.
  See #​2866
• [ByRef] bytes UDL arguments now map to &[u8] on the Rust side instead of &Vec<u8>. UDL-defined functions whose Rust implementations take &Vec<u8> must change to &[u8]. Proc-macro signatures (fn foo(x: &[u8])) are unchanged. On the Kotlin side, call sites must now pass a direct java.nio.ByteBuffer rather than ByteArray; migrate with ByteBuffer.allocateDirect(arr.size).put(arr).flip(). Swift (Data) and Python (bytes) call sites are unchanged. (#​2878)
• Reworked the experimental pipeline bindgen code. Any external binding generators using this will
  need to be reworked as well. See #​2787 for
  examples of how this can be done.

What's Fixed

• Fixed bug that sometimes prevented renaming items inside a submodule #​2792
• Exempted UniFfiTag from clippy::exhaustive_structs since downstream projects may depend on it #​2809
• Ruby: Code for all kinds of enums and custom types is now correctly generated #​2880 and #​2891

⚠️ Breaking Changes for external bindings authors ⚠️

• There's a new GlobalConfig struct for managing config. It replaces BindgenPathsLayer::get_config() method which has been removed. See #​2866.
• [ByRef] bytes arguments now travel across the FFI as a ForeignBytes (pointer + length) value rather than a RustBuffer. External bindings need to accept the foreign-language byte buffer at the call site and lower it to ForeignBytes for the duration of the call (no copy). (#​2878)

What's New?

• Global config file support via --config. See the docs.

• Traits can now be exported with #[uniffi::export(foreign)] for foreign-only implementations, or #[uniffi::export(rust, foreign)] for both Rust and foreign implementations. The with_foreign flag is deprecated in favor of rust, foreign.

• Recursive enums are now supported. UniFFI automatically detects when enum and record types participate in cycles — self-referential, mutually recursive, or cycling through a record — and generates appropriate bindings: indirect in Swift, forward references in Python (#​2834).

• Box<T> now automatically implements FFI traits when T implements them, allowing direct use in enum variants and function parameters without NewType wrappers (#​2808)

• Record fields can now be renamed with the proc-macro name = "new_field_name" attribute (#​2794)

• Items can be excluded from the generated bindings using uniffi.toml.

• Added mutable_records configuration option to allow specific records to remain mutable even when generate_immutable_records is enabled (Kotlin and Swift).

• Kotlin objects now have an uniffiIsDestroyed property that returns true if the Rust reference no longer exists (#​2825)

• Updated askama version to 0.15.6

• Custom Types can have docstrings in some languages (#​2853)

• Ruby: Expose standard Rust traits for generated ruby code (#​2883)

• Ruby: Add support for sync foreign traits (#​2916)

• Ruby: Add async support (#​2923)

• Added zero-copy transfer of &[u8] / [ByRef] bytes arguments from foreign code to Rust. Kotlin (java.nio.ByteBuffer, must be direct), Swift (Data), and Python (bytes-like, buffer protocol) pass byte buffers as pointer + length (ForeignBytes) rather than copying through RustBuffer. Not yet supported on Ruby, and not yet supported in async functions on any language (#​2878).

• #[uniffi::export(async_runtime = "tokio")] can now be applied to trait exports, wrapping each method's FFI scaffolding future in async_compat::Compat the same way it does for inherent impls and free functions (#​2899).

• Added support for using HashSet with proc-macros

• Allow literal number suffix with derive(uniffi::Enum)(#​2926)

All changes in v0.32.0.

v0.31.2

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What's Fixed

• Kotlin: Fixed JNA direct-mapped u8/u16 return values by widening the internal return carrier to Int, which avoids signedness mismatches during checksum validation and other direct-return paths on Android ARM32. (#​2897)
• Kotlin: Fix async functions that return an external/RustBuffer type
• Swift: Fixed FfiConverterString silently stripping a leading U+FEFF byte order mark from Rust strings.
• Swift: Prevent strict concurrency warning with callback interface tables

All changes in v0.31.2.

v0.31.1

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What's Fixed

• Kotlin: Fixed JNA direct-mapped u8/u16 return values by widening the internal return carrier to Int, which avoids signedness mismatches during checksum validation and other direct-return paths on Android ARM32. (#​2897)
• Kotlin: Fix async functions that return an external/RustBuffer type
• Swift: Fixed FfiConverterString silently stripping a leading U+FEFF byte order mark from Rust strings.
• Swift: Prevent strict concurrency warning with callback interface tables

All changes in v0.31.2.

v0.31.0

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What's Fixed

• Swift: Fixed iOS crash when address sanitizer is enabled
  #​2821
• Swift: Fixed memory link in async code
  #​2854

All changes in v0.31.1.