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71 lines
2.8 KiB
71 lines
2.8 KiB
const copyProperty = (to, from, property, ignoreNonConfigurable) => { |
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// `Function#length` should reflect the parameters of `to` not `from` since we keep its body. |
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// `Function#prototype` is non-writable and non-configurable so can never be modified. |
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if (property === 'length' || property === 'prototype') { |
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return; |
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} |
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// `Function#arguments` and `Function#caller` should not be copied. They were reported to be present in `Reflect.ownKeys` for some devices in React Native (#41), so we explicitly ignore them here. |
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if (property === 'arguments' || property === 'caller') { |
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return; |
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} |
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const toDescriptor = Object.getOwnPropertyDescriptor(to, property); |
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const fromDescriptor = Object.getOwnPropertyDescriptor(from, property); |
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if (!canCopyProperty(toDescriptor, fromDescriptor) && ignoreNonConfigurable) { |
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return; |
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} |
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Object.defineProperty(to, property, fromDescriptor); |
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}; |
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// `Object.defineProperty()` throws if the property exists, is not configurable and either: |
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// - one its descriptors is changed |
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// - it is non-writable and its value is changed |
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const canCopyProperty = function (toDescriptor, fromDescriptor) { |
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return toDescriptor === undefined || toDescriptor.configurable || ( |
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toDescriptor.writable === fromDescriptor.writable && |
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toDescriptor.enumerable === fromDescriptor.enumerable && |
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toDescriptor.configurable === fromDescriptor.configurable && |
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(toDescriptor.writable || toDescriptor.value === fromDescriptor.value) |
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); |
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}; |
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const changePrototype = (to, from) => { |
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const fromPrototype = Object.getPrototypeOf(from); |
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if (fromPrototype === Object.getPrototypeOf(to)) { |
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return; |
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} |
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Object.setPrototypeOf(to, fromPrototype); |
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}; |
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const wrappedToString = (withName, fromBody) => `/* Wrapped ${withName}*/\n${fromBody}`; |
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const toStringDescriptor = Object.getOwnPropertyDescriptor(Function.prototype, 'toString'); |
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const toStringName = Object.getOwnPropertyDescriptor(Function.prototype.toString, 'name'); |
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// We call `from.toString()` early (not lazily) to ensure `from` can be garbage collected. |
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// We use `bind()` instead of a closure for the same reason. |
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// Calling `from.toString()` early also allows caching it in case `to.toString()` is called several times. |
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const changeToString = (to, from, name) => { |
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const withName = name === '' ? '' : `with ${name.trim()}() `; |
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const newToString = wrappedToString.bind(null, withName, from.toString()); |
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// Ensure `to.toString.toString` is non-enumerable and has the same `same` |
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Object.defineProperty(newToString, 'name', toStringName); |
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Object.defineProperty(to, 'toString', {...toStringDescriptor, value: newToString}); |
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}; |
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export default function mimicFunction(to, from, {ignoreNonConfigurable = false} = {}) { |
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const {name} = to; |
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for (const property of Reflect.ownKeys(from)) { |
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copyProperty(to, from, property, ignoreNonConfigurable); |
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} |
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changePrototype(to, from); |
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changeToString(to, from, name); |
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return to; |
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}
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