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Upgrading v0.28.x -> v0.29.x

We've made a number of breaking changes in this release, particularly to:

  • Custom types: UniffiCustomTypeConverter has been removed.
  • External types: extern has been removed; you must describe the type.

Custom types

Custom types still implemented via the UniffiCustomTypeConverter trait must move to proc-macros.

Before:

impl UniffiCustomTypeConverter for NewCustomType {
    type Builtin = BridgeType;

    fn into_custom(val: Self::Builtin) -> uniffi::Result<Self> {
        ...
    }

    fn from_custom(obj: Self) -> Self::Builtin {
        ...
    }
}

After:

uniffi::custom_type!(NewCustomType, BridgeType, {
    try_lift: |val| { Ok(...) },
    lower: |obj| { ... },
})

The custom_type! macro is more flexible than the old system - eg, the closures can be omitted in many cases where From and Into exist. See the Custom Types for details.

External Types

External types can no longer be described in UDL via extern - instead, you must specify the type.

For example: 

[External="crate_name"]
typedef extern MyEnum;
is no longer accepted - you must use, eg: 
[External="crate_name"]
typedef enum MyEnum;

Edge-cases broken include:

  • Different variations of the External attribute (eg, [ExternalInterface]) are no longer supported; eg, [ExternalInterface=".."] typedef extern ... becomes [External=".."] typedef interface ... )
  • The [Rust=..] attribute has been removed - you should just remove the attribute entirely.

See Remote and External Types for more detail.

External Custom Types

Previously you could describe an external Custom Type Url in UDL as: 

[External="crate_name"]
typedef extern Url;

But now you must use: 

[Custom="crate_name"]
typedef string Url; // replace `string` with any appropriate type.

Remote Types

The macros ffi_converter_forward and all use_* macros (eg, use_udl_record!, use_udl_object!, use_udl_enum! etc) are now unnecessary so have been removed.

See Remote and External Types for more detail.

Shared Rust/UDL types

The Rust attribute has been removed - use the same typedef syntax described above for External Types.

[Rust="record"]
typedef extern One;
becomes a typedef with no attributes 
typedef record One;