fix: preserve dump entries when loading TTL values

src/index.ts

@@ -2113,17 +2113,18 @@ export class LRUCache<K extends {}, V extends {}, FC = unknown> {
   load(arr: [K, LRUCache.Entry<V>][]) {
     this.clear()
     for (const [key, entry] of arr) {
-      if (entry.start) {
+      const options = { ...entry }
+      if (options.start) {
         // entry.start is a portable timestamp, but we may be using
         // node's performance.now(), so calculate the offset, so that
         // we get the intended remaining TTL, no matter how long it's
         // been on ice.
         //
         // it's ok for this to be a bit slow, it's a rare operation.
-        const age = Date.now() - entry.start
-        entry.start = this.#perf.now() - age
+        const age = Date.now() - options.start
+        options.start = this.#perf.now() - age
       }
-      this.#set(key, entry.value, entry)
+      this.#set(key, entry.value, options)
     }
   }
 

test/load.ts

@@ -10,3 +10,24 @@ const d = new LRU(c)
 d.load(c.dump())
 
 t.strictSame(d, c)
+
+t.test('loading TTL entries does not mutate the reusable dump', t => {
+  const source = new LRU<string, string>({ max: 5, ttl: 60_000 })
+  source.set('key', 'value')
+  const entries = source.dump()
+  const snapshot = structuredClone(entries)
+  const first = new LRU<string, string>({ max: 5 })
+  const second = new LRU<string, string>({ max: 5 })
+
+  first.load(entries)
+  t.strictSame(
+    entries,
+    snapshot,
+    'preserves portable timestamps in the input',
+  )
+  second.load(entries)
+  t.equal(first.get('key'), 'value')
+  t.equal(second.get('key'), 'value')
+  t.ok(second.getRemainingTTL('key') > 0)
+  t.end()
+})