test: pin draft prototype-inspection behavior restored by #1271#1
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test: pin draft prototype-inspection behavior restored by #1271#1jonatankruszewski wants to merge 1 commit into
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Drafts must stay safe for ecosystem introspection idioms: lodash's isPrototype (used by isEmpty/isEqual/isPlainObject) reads value.constructor.prototype, and fast-deep-equal compares constructor identity. The guard reverted in immerjs#1271 broke these (immerjs#1265, immerjs#1266, immerjs#1268) while its tests still passed, because try/catch made a crash and a successful block indistinguishable. These tests assert observable behavior directly, so they fail on 11.1.9-11.1.11 (verified: constructor.prototype throws, constructor identity and 'in' checks break, writes to own keys named prototype are dropped) and pass on main. setPrototypeOf remains forbidden; the applyPatches-layer pollution guards in patch.js are untouched.
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Self-review PR — diff preview before opening against
immerjs:main.Follow-up to immerjs#1271, as offered in immerjs#1269.
The revert restored draft behavior that ecosystem libraries depend on, but that behavior is currently untested — the produce-side tests from immerjs#1259 were removed along with the guard, and the remaining pollution tests all live at the
applyPatcheslayer. This PR adds test-only coverage (no source changes) that pins the restored contract:draft.constructoris the real constructor (Object/Array/the class), with stable identity across drafts — thefast-deep-equalregression from Regression when comparing equality usingfast-deep-equalimmerjs/immer#1266draft.constructor.prototypeis readable and real — thelodash.isEmpty/isEqualcrashes from TypeError: 'get' on proxy: property 'prototype' is a read-only and non-configurable data property on the proxy target immerjs/immer#1265 and lodash.isEmpty() on a draft throws "TypeError: 'get' on proxy: property 'prototype'..." since 11.1.9 immerjs/immer#1268, exercised via lodash'sisPrototypeidiom replicated inline (no new devDependency)'constructor' in draftand own data keys namedconstructor/prototyperound-trip__proto__reads resolve to the real prototypeObject.setPrototypeOf(draft, …)still throws — the restrictive half of the contract is pinned tooThe tests assert observable behavior directly rather than wrapping attacks in
try/catch, so a crash and a successful defense are distinguishable. Verified: they fail on 11.1.9–11.1.11 (constructor.prototypethrows, constructor identity andinbreak, writes to an own key namedprototypeare dropped) and pass onmain.If a convincing case for hardening comes up later, these tests define what any future guard must preserve. The
applyPatches-layer guards inpatch.jsare untouched.Full suite: 3689 passed, 8 skipped (pre-existing).