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node_modules/stylelint/lib/utils/putIfAbsent.mjs

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+/**
+ * If `map` already has the given `key`, returns its value. Otherwise, calls
+ * `callback`, adds the result to `map` at `key`, and then returns it.
+ *
+ * @template K
+ * @template V
+ * @param {Map<K, V>} map
+ * @param {K} key
+ * @param {() => V} callback
+ * @returns {V}
+ */
+export default function putIfAbsent(map, key, callback) {
+	if (map.has(key)) return /** @type {V} */ (map.get(key));
+
+	const value = callback();
+
+	map.set(key, value);
+
+	return value;
+}