fix(engines): guard usePdfiumEngine success path against cancellation (Strict Mode)#700
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fix(engines): guard usePdfiumEngine success path against cancellation (Strict Mode)#700junwen-k wants to merge 1 commit into
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The init effect only checked its `cancelled` flag on the error path, so under React Strict Mode's dev mount/unmount/remount it created two engines and called `setEngine` for both. The second engine identity remounts any consumer keyed on the engine (e.g. `<EmbedPDF>`), abandoning an in-flight document load, and the first engine leaks because the cleanup that ran saw `engineRef.current === null`. Discard the freshly created engine if the effect was already torn down, and factor engine disposal into a `disposeEngine` helper so teardown captures its target locally — a `wasmUrl` change mid-init can no longer destroy the replacement engine from within the old close callback. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
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Problem
usePdfiumEngine's init effect only checks itscancelledflag on the error path — the success path always callssetEngine. Under React Strict Mode (Next.js dev default), the effect mounts → cleans up → remounts before the firstcreatePdfiumEngineresolves. Cleanup ran whileengineRef.currentwas stillnull, so it disposed nothing; then both invocations resolve and callsetEnginewith two different engine identities.Result: any consumer keyed on the engine (e.g.
<EmbedPDF>, keyed on[engine, plugins]) remounts, abandoning an in-flight document load, and the first engine leaks.Fix
Check
cancelledafter the engine is created; if the effect was already torn down, dispose the freshly created engine and return before committing it. Engine disposal is factored into a smalldisposeEngine(engine)helper, which also captures the engine locally in the teardown path — so awasmUrlchange mid-init can no longer destroy the replacement engine from inside the old close callback.ignoreis already imported and used, so no new imports. This is the shared React/Preact hook; the Svelte/Vue variants don't share it and are untouched. Includes a patch changeset for@embedpdf/engines.