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structured clone - #3637
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structured clone#3637
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Jarred-Sumner
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Jul 15, 2023
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❌ @dylan-conway 7 files with test failures on bun-darwin-aarch64:
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❌ @dylan-conway 4 files with test failures on linux-x64-baseline:
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❌ @dylan-conway 4 files with test failures on linux-x64:
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❌ @dylan-conway 7 files with test failures on bun-darwin-x64-baseline:
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Jarred-Sumner
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Jun 27, 2026
) ## Summary Serializing a graph that contains a detached `ArrayBuffer` threw a plain `TypeError` instead of a `"DataCloneError"` `DOMException`. The [HTML structured serialize algorithm](https://html.spec.whatwg.org/multipage/structured-data.html#structuredserializeinternal) requires `DataCloneError` here, and Node, Chrome, Firefox, and Safari all throw it. Code that branches on `DataCloneError` (the standard "unclonable value" signal, e.g. retry-without-transfer fallbacks) takes the wrong branch on Bun. ## Reproduction ```js const ab = new ArrayBuffer(8); structuredClone(ab, { transfer: [ab] }); // detach it try { structuredClone({ ab }); } catch (e) { console.log(e.name); } // Bun: "TypeError" Node / browsers: "DataCloneError" ``` Before the fix: ``` TypeError: Unable to deserialize data. ``` ## Cause The detached check in `CloneSerializer::dumpIfTerminal` set `SerializationReturnCode::ValidationError`, which `maybeThrowExceptionIfSerializationFailed` maps to a `TypeError`: ```cpp if (auto* arrayBuffer = toPossiblySharedArrayBuffer(vm, obj)) { if (arrayBuffer->isDetached()) { code = SerializationReturnCode::ValidationError; // -> TypeError ``` Upstream WebKit uses `DataCloneError` at this exact site. Bun's port of `SerializedScriptValue.cpp` (#3637, 2023) predates that upstream change and kept the old code. ## Fix Set `SerializationReturnCode::DataCloneError` instead. One line; no wire format change. This covers every entry point that shares the serializer: `structuredClone`, `Worker`/`MessagePort` `postMessage`, `bun:jsc` `serialize`, and `node:v8` `serialize`. Detached ArrayBuffers reached through a typed array or `DataView` already threw `DataCloneError` (they hit the `isOutOfBounds` check first), as did a detached buffer passed in the transfer list; only a direct reference to a detached `ArrayBuffer` in the serialized graph was wrong. Not changed: a `MessagePort` that appears in the graph but not in the transfer list still throws `TypeError`. That path also uses `ValidationError`, but it matches current upstream WebKit, so it is out of scope here. ## Verification The new test in `test/js/web/workers/structured-clone.test.ts` serializes a detached `ArrayBuffer` bare, inside an object, inside an array, and inside a `Map`, and asserts the thrown value is a `DOMException` named `DataCloneError` with `code === DOMException.DATA_CLONE_ERR`. <details> <summary>Before (unfixed) and after</summary> ``` # USE_SYSTEM_BUN=1 bun test structured-clone.test.ts -t "Serializing a detached ArrayBuffer" error: expect(received).toBeInstanceOf(expected) Expected constructor: [class DOMException] TypeError: Unable to deserialize data. (fail) structuredClone > transferables > Serializing a detached ArrayBuffer throws DataCloneError # bun bd test structured-clone.test.ts 162 pass, 0 fail ``` </details>
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