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fix(transform-spread): copy constant array when later elements have side effects - #18613
hoanle0126 wants to merge 2 commits into
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| let lastImpureIndex = -1; | ||
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| for (const prop of props) { | ||
| if (!iterableIsArray) { |
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The lastImpureIndex is computed only when iterableIsArray is false, so under iterableIsArray assumption, the #18531 is still not fixed.
Given the input [...a, a.push(3)], under this assumption, we can emit
[].concat(a.slice(), [a.push(3)])so it still outputs [1, 2, 3]. Could you implement it and add a new test case for the iterableIsArray assumption case?
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Good catch, updated to emit .slice() under iterableIsArray when a later element has side effects and added a test fixture for it.
JLHwung
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PR: Bug Fix 🐛
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When an array is spread before impure elements (such as
[...a, a.push(3)]), passingadirectly to.concat(...)evaluates the later arguments before readinga. Clone the spread argument whenever a subsequent element may have side effects (toConsumableArrayfor constantArraybindings by default, or.slice()under theiterableIsArrayassumption).