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38 lines
1.2 KiB
JavaScript
38 lines
1.2 KiB
JavaScript
"use strict";
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// A strict deep-merging implementation that *only* merges regular objects, and prevents prototype pollution
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function isObject(value) {
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// TODO: Disallow special object types, for statically defined values (or just disallow specifying static values in the root schema in dlayer?)
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return (value != null && typeof value === "object" && !Array.isArray(value));
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}
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module.exports = function deepMerge(a, b) {
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let merged = Object.create(null);
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let keys = new Set([ ... Object.keys(a), ... Object.keys(b) ]);
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for (let key of keys) {
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// Technically over-blocks *any* 'constructor' key
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if (key === "__proto__" || key === "constructor") {
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continue;
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}
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let valueA = a[key];
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let valueB = b[key];
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if (isObject(valueA) && valueB === undefined) {
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merged[key] = valueA;
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} else if (isObject(valueB) && valueA === undefined) {
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merged[key] = valueB;
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} else if (isObject(valueA) && isObject(valueB)) {
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merged[key] = deepMerge(valueA, valueB);
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} else if (!isObject(valueA) && !isObject(valueB)) {
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merged[key] = valueB ?? valueA;
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} else {
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// FIXME: Identifiable error type, and include the error path as well
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throw new Error("Cannot merge non-object into object");
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}
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}
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return merged;
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}; |