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[`__proto__`] is a special property to access an object's prototype. It has many pitfalls: - Setting it to an object value changes an object's prototype, which is generally discouraged and may be unexpected by the `iterator` callback. - Setting it to a non-object value does nothing (meaning `seen[k] = true` has no effect). - When Node.js is run with the [`--disable-proto=throw`] option, getting or setting `__proto__` causes an exception with code `ERR_PROTO_ACCESS` to be thrown. Additionally, since this property (and all properties of `Object.prototype`) are currently unused in this project by consumers of `walk()`, it is both safe and preferable to exclude. [`__proto__`]: https://tc39.es/ecma262/multipage/fundamental-objects.html#sec-object.prototype.__proto__ [`--disable-proto=throw`]: https://nodejs.org/api/cli.html#disable-protomode Fixes: sinonjs#2695 Signed-off-by: Kevin Locke <kevin@kevinlocke.name>
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Purpose (TL;DR) - mandatory
Fix issue #2695 by excluding
__proto__fromwalk().Background (Problem in detail) - optional
__proto__is a special property to access an object's prototype. It has many pitfalls:iteratorcallback.seen[k] = truehas no effect).--disable-proto=throwoption, getting or setting__proto__causes an exception with codeERR_PROTO_ACCESSto be thrown, which causes issues like Change in 21.1: sinon.stub() throws with--disable-proto=throw#2695.Solution - optional
Since
__proto__(and all properties ofObject.prototype) are currently unused by consumers ofwalk()in this project, it is both safe and preferable to exclude it from enumeration bywalk().How to verify - mandatory
npm installNODE_OPTIONS=--disable-proto=throw npm testChecklist for author
npm run lintpassesAdditional Work
It would be great if
--disable-proto=throwcould be added to the test suite, either by adding--node-option disable-proto=throwto the mocha invocation intest-node, or adding a separate run to test under these conditions. However, this may introduce an additional maintenance burden, so requires additional discussion and is not currently part of this PR.Thanks for considering,
Kevin