Function once

valdi/vscode_debugger/src/common/objUtils.ts:190–210

(
  fn: (...args: Args) => T,
)

 * the result.
 */
export function once<T, Args extends unknown[]>(
  fn: (...args: Args) => T,
): ((...args: Args) => T) & { value?: T; forget(): void } {
  let value: T | typeof unset = unset;
  const onced = (...args: Args) => {
    if (value === unset) {
      onced.value = value = fn(...args);
    }

    return value;
  };

  onced.forget = () => {
    value = unset;
    onced.value = undefined;
  };

  onced.value = undefined as T | undefined;

  return onced;
}

/**
 * Memoizes the single-parameter function.