wasm-bindgen 0.2.109

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Created by brew bump

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release notes

### Added


Added support for erasable generic type parameters on imported JavaScript types,

using sound type erasure in JS bindgen boundary. Includes updated js-sys bindings

with generic implementations for many standard JS types and functions including

Array<T>, Promise<T>, Map<K, V>, Iterator<T>, and more.

#4876


Added ScopedClosure<'a, T> as a unified closure type with lifetime parameter. ScopedClosure::borrow(&f) (for immutable Fn) and ScopedClosure::borrow_mut(&mut f) (for mutable FnMut) create borrowed closures that can capture non-'static references, ideal for immediate/synchronous JS callbacks. Closure<T> is now a type alias for ScopedClosure<'static, T>, maintaining backwards compatibility. Also added IntoWasmAbi implementation for Closure<T> enabling pass-by-value ownership transfer to JavaScript.


Added ImmediateClosure<'a, T> as a lightweight, unwind-safe replacement for

&dyn FnMut in immediate/synchronous callbacks. Unlike ScopedClosure, it has

no JS call on creation, no JS call on drop, and no GC overhead—the same ABI as

&dyn FnMut but with panic safety. Use ImmediateClosure::new(&f) for

immutable Fn closures (easier to satisfy unwind safety) or ImmediateClosure::new_mut(&mut f) for

mutable FnMut closures. Closure parameter types are automatically inferred from context.

Also implements From<&ImmediateClosure<T>> for ScopedClosure<T> for API migration.

#4950


Implement #[wasm_bindgen(catch)] exception handling directly in Wasm using

WebAssembly.JSTag when Wasm exception handling is available. This generates

smaller and faster code by avoiding JavaScript handleError wrapper functions.

#4942


Add Node.js worker_threads support for atomics builds. When targeting Node.js with atomics enabled, wasm-bindgen now generates initSync({ module, memory, thread_stack_size }) and __wbg_get_imports(memory) functions that allow worker threads to initialize with a shared WebAssembly.Memory and pre-compiled module. Auto-initialization occurs only on the main thread for backwards compatibility.


Added a panic message when a getter has more than one argument.

#4936


Added support for WebIDL namespace attributes in wasm-bindgen-webidl. This enables

APIs like the CSS Custom Highlight API which adds the highlights attribute to the CSS namespace.

#4930


Added stable ShowPopoverOptions dictionary and show_popover_with_options() method to

HtmlElement, and unstable TogglePopoverOptions dictionary per the WHATWG HTML spec.

#4968


Added unstable Geolocation API types per the latest W3C spec: GeolocationCoordinates,

GeolocationPosition, and GeolocationPositionError. The Geolocation interface now

has both stable methods (using the old Position/PositionError types with [Throws])

and unstable methods (using the new types without [Throws]}, matching actual browser behavior).

#2578


Added matrixTransform() method to DOMPointReadOnly in web-sys.

#4962


Added the web and node targets to the --experimental-reset-state-function flag.

#4909


Added oncancel event handler to GlobalEventHandlers (available on HtmlElement,

Document, Window, etc.).

#4542


Added CommandEvent and CommandEventInit from the Invoker Commands API.

#4552


Added AbstractRange, StaticRange, and StaticRangeInit interfaces.

#4221


Updated WebCodecs API to Working Draft 2026-01-29 and MediaRecorder API to 2025-04-17.

Added rotation and flip to VideoDecoderConfig.

#4411


Added support for unstable WebIDL to override stable attribute types, allowing

corrected type signatures behind web_sys_unstable_apis. Applied to MouseEvent

coordinate attributes (clientX, clientY, screenX, screenY, offsetX,

offsetY, pageX, pageY) which now return f64 instead of i32 when

unstable APIs are enabled, per the CSSOM View spec draft.

#4935


Added support for unstable WebIDL to override stable method return types. This

enables User Timing Level 3 APIs where Performance.mark() and Performance.measure()

return PerformanceMark and PerformanceMeasure respectively (instead of undefined)

when web_sys_unstable_apis is enabled. Also added PerformanceMarkOptions,

PerformanceMeasureOptions, and the detail attribute on marks/measures.

#3734


Added non-standard mode option for FileSystemFileHandle.createSyncAccessHandle().

Also improved WebIDL generator to track stability at the signature level, allowing

stable methods to have unstable overloads.

#4928


Updated WebGPU bindings to the February 2026 spec. Dictionary fields with union

types now generate multiple type-safe setters (e.g. set_resource_gpu_sampler(),

set_resource_gpu_texture_view()) alongside a deprecated fallback setter. Sequence

arguments in unstable APIs now use typed slices (&[T]) instead of &JsValue.

Fixed inner string enum types to use JsString in generic positions, added BigInt

to builtin identifiers, and fixed dictionary field feature gates to not over-constrain

getters with setter type requirements.

#4955


Improved dictionary union type expansion: stable fallback setters are no longer

deprecated, and unstable builder methods now use the first typed variant instead

of &JsValue. Dictionaries with required union fields now generate expanded

constructors for each variant (e.g. new(), new_with_gpu_texture_view()),

with duplicate-signature variants elided.

#4966


Changed


Increased externref stack size from 128 to 1024 slots to prevent "table index is out of bounds"

errors in applications with deep call stacks or many concurrent async operations.

#4951


Closure::new(), Closure::once(), and related methods now require UnwindSafe bounds on closures when building with panic=unwind. New _aborting variants (new_aborting(), once_aborting(), etc.) are provided for closures that don't need panic catching and want to avoid the UnwindSafe requirement.

#4893


global does not use the unsafe-eval new Function trick anymore allowing to have CSP strict compliant packages with wasm-bindgen.

#4910


eval and Function constructors are now gated behind the unsafe-eval feature.

#4914


Fixed


Fixed incorrect JS export names when LLVM merges identical functions at opt-level >= 2.

#4946


Fixed incorrect Closure adapter deduplication when wasm-ld's Identical Code Folding merges

invoke functions for different closure types into the same export.

#4953


Fixed ReferenceError when using Rust struct names that conflict with JS builtins (e.g., Array).

The constructor now correctly uses the aliased FinalizationRegistry identifier.

#4932


Fixed Element::scroll_top(), Element::scroll_left(), and HtmlElement::scroll_top()

to return f64 instead of i32 per the CSSOM View spec, behind web_sys_unstable_apis.

The stable API is unchanged for backwards compatibility.

#4525


Added spec-compliant i32 parameter types for CanvasRenderingContext2d::get_image_data()

and put_image_data() (and OffscreenCanvasRenderingContext2d equivalents) behind

web_sys_unstable_apis. Per the HTML spec, getImageData and putImageData use long

(i32) for coordinates, not double (f64). The stable API is unchanged for backwards

compatibility.

#1920


Fixed incorrect #[cfg(web_sys_unstable_apis)] gating on stable method signatures that

share a WebIDL operation with unstable overloads. For example, Clipboard.read() (0 args)

was incorrectly gated as unstable because the unstable read(options) overload existed.

The WebIDL code generator now uses an authoritative expansion model where stable and unstable

signature sets are built independently and compared: identical signatures merge (no gate),

stable-only signatures get not(unstable), and unstable-only signatures get unstable.

Also adds typed generics (Promise<T>, Array<T>, Function<fn(...)>, etc.) to all

unstable API methods, and adds missing PhotoCapabilities, PhotoSettings,

MediaSettingsRange, Point2D, RedEyeReduction, FillLightMode, and MeteringMode

types from the W3C Image Capture spec.

#4964


Fixed unfulfilled_lint_expectations warnings when using #[expect(...)] attributes

on functions annotated with #[wasm_bindgen]. The #[expect] attributes are now

converted to #[allow] in generated code to prevent spurious warnings.

#4409

View the full release notes at https://github.com/wasm-bindgen/wasm-bindgen/releases/tag/0.2.109.

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