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This patch revamps the wasm backend's JSFFI internal implementation and documentation: - `JSValManager` logic to allocate a key is simplified to simple bumping. According to experiments with all major browsers, the internal `Map` would overflow the heap much earlier before we really exhaust the 32-bit key space, so there's no point in the extra complexity. - `freeJSVal` is now idempotent and safe to call more than once. This is achieved by attaching the `StablePtr#` to the `JSVal#` closure and nullifying it when calling `freeJSVal`, so the same stable pointer cannot be double freed. - `mkWeakJSVal` no longer exposes the internal `Weak#` pointer and always creates a new `Weak#` on the fly. Otherwise by finalizing that `Weak#`, user could accidentally drop the `JSVal`, but `mkWeakJSVal` is only supposed to create a `Weak` that observes the `JSVal`'s liveliness without actually interfering it. - `PromisePendingException` is no longer exported since it's never meant to be caught by user code; it's a severe bug if it's actually raised at runtime. - Everything exported by user-facing `GHC.Wasm.Prim` now has proper haddock documentation. - Note [JSVal representation for wasm] has been updated to reflect the new JSVal# memory layout.
This patch revamps the wasm backend's JSFFI internal implementation and documentation: - `JSValManager` logic to allocate a key is simplified to simple bumping. According to experiments with all major browsers, the internal `Map` would overflow the heap much earlier before we really exhaust the 32-bit key space, so there's no point in the extra complexity. - `freeJSVal` is now idempotent and safe to call more than once. This is achieved by attaching the `StablePtr#` to the `JSVal#` closure and nullifying it when calling `freeJSVal`, so the same stable pointer cannot be double freed. - `mkWeakJSVal` no longer exposes the internal `Weak#` pointer and always creates a new `Weak#` on the fly. Otherwise by finalizing that `Weak#`, user could accidentally drop the `JSVal`, but `mkWeakJSVal` is only supposed to create a `Weak` that observes the `JSVal`'s liveliness without actually interfering it. - `PromisePendingException` is no longer exported since it's never meant to be caught by user code; it's a severe bug if it's actually raised at runtime. - Everything exported by user-facing `GHC.Wasm.Prim` now has proper haddock documentation. - Note [JSVal representation for wasm] has been updated to reflect the new JSVal# memory layout.
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