// Copyright 2018-2025 the Deno authors. MIT license.
import type { MemoizationCache } from "./memoize.ts";
/**
* Default serialization of arguments list for use as cache keys. Equivalence
* follows [`SameValueZero`](https://tc39.es/ecma262/multipage/abstract-operations.html#sec-samevaluezero)
* reference equality, such that `getKey(x, y) === getKey(x, y)` for all values
* of `x` and `y`, but `getKey({}) !== getKey({})`.
*
* @param cache The cache for which the keys will be used.
* @returns `getKey`, the function for getting cache keys.
*/
export function _serializeArgList<Return>(
cache: MemoizationCache<unknown, Return>,
): (this: unknown, ...args: unknown[]) => string {
const weakKeyToKeySegmentCache = new WeakMap<WeakKey, string>();
const weakKeySegmentToKeyCache = new Map<string, string[]>();
let i = 0;
const registry = new FinalizationRegistry<string>((keySegment) => {
for (const key of weakKeySegmentToKeyCache.get(keySegment) ?? []) {
cache.delete(key);
}
weakKeySegmentToKeyCache.delete(keySegment);
});
return function getKey(...args) {
const weakKeySegments: string[] = [];
const keySegments = [this, ...args].map((arg) => {
if (typeof arg === "undefined") return "undefined";
if (typeof arg === "bigint") return `${arg}n`;
if (typeof arg === "number") {
return String(arg);
}
if (
arg === null ||
typeof arg === "string" ||
typeof arg === "boolean"
) {
// This branch will need to be updated if further types are added to
// the language that support value equality,
// e.g. https://github.com/tc39/proposal-record-tuple
return JSON.stringify(arg);
}
try {
assertWeakKey(arg);
} catch {
if (typeof arg === "symbol") {
return `Symbol.for(${JSON.stringify(arg.description)})`;
}
// Non-weak keys other than `Symbol.for(...)` are handled by the branches above.
throw new Error(
"Should be unreachable: please open an issue at https://github.com/denoland/std/issues/new",
);
}
if (!weakKeyToKeySegmentCache.has(arg)) {
const keySegment = `{${i++}}`;
weakKeySegments.push(keySegment);
registry.register(arg, keySegment);
weakKeyToKeySegmentCache.set(arg, keySegment);
}
const keySegment = weakKeyToKeySegmentCache.get(arg)!;
weakKeySegments.push(keySegment);
return keySegment;
});
const key = keySegments.join(",");
for (const keySegment of weakKeySegments) {
const keys = weakKeySegmentToKeyCache.get(keySegment) ?? [];
keys.push(key);
weakKeySegmentToKeyCache.set(keySegment, keys);
}
return key;
};
}
function assertWeakKey(arg: unknown): asserts arg is WeakKey {
new WeakRef(arg as WeakKey);
}
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