fix: vnode clone compatible with frozen intrinsics#5078
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kumavis wants to merge 1 commit intopreactjs:mainfrom
Open
fix: vnode clone compatible with frozen intrinsics#5078kumavis wants to merge 1 commit intopreactjs:mainfrom
kumavis wants to merge 1 commit intopreactjs:mainfrom
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Object.assign({}, vnode) in renderComponent() (and cloneNode in
src/diff/index.js) tries to copy a vnode's `constructor: undefined`
own property via [[Set]]. Under https://hardenedjs.org/ environment the default
overrideTaming makes Object.prototype.constructor non-writable, so
the assignment fails with:
TypeError: Cannot assign to read only property 'constructor'
Initial render works because createVNode builds vnodes with an
object literal ([[CreateDataProperty]], not Set), but any
setState/forceUpdate-triggered re-render goes through
Object.assign({}, oldVNode) and trips the override mistake.
kumavis
changed the title
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coverage: 98.666%. remained the same — kumavis:fix-hardenedjs-compat into preactjs:main |
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This PR fixes a compatibility issue when Preact is run in Hardened JavaScript environments such as:
The compatibility issue comes from a javascript quirk known as "the override mistake" related to frozen intrinsics. For this bug, the minimal environment change is just
Object.freeze(Object.prototype).In this environment, assigning the
constructorproperty via assignment syntax (=) orObject.assigncauses an error.Specifically,
Object.assign({}, vnode)inrenderComponent()(andcloneNodeinsrc/diff/index.js) tries to copy a vnode'sconstructor: undefinedown property via[[Set]]. Under environments with a frozenObject.prototypetheObject.prototype.constructoris non-writable, so the assignment fails.This PR introduces a
cloneVNodeutility that ensuresVNodesare cloned safely. It also reorders theconstructorkey for consistent object shape betweenVNodesand their clones.Note: I erred on the side of excessive documentation in comments, let me know if you would like this reduced.