fix: always return promise in close() (#1359)

Updates the `close` method to always return a `Promise` rather than
having a mixed return type.

We do not need to check `closed` since we only care if the close
logic/promise has already started, so switching the condition should be
enough.

src/index.ts

@@ -448,6 +448,7 @@ export class FSWatcher extends EventEmitter {
  add(paths_: Path | Path[], _origAdd?: string, _internal?: boolean): FSWatcher {
  const { cwd } = this.options;
  this.closed = false;
+ this._closePromise = undefined;
  let paths = unifyPaths(paths_);
  if (cwd) {
  paths = paths.map((path) => {
@@ -524,13 +525,15 @@ export class FSWatcher extends EventEmitter {
  /**
  * Close watchers and remove all listeners from watched paths.
  */
- close(): Promise<void> | undefined {
- if (this.closed) return this._closePromise;
+ close(): Promise<void> {
+ if (this._closePromise) {
+ return this._closePromise;
+ }
  this.closed = true;
 
  // Memory management.
  this.removeAllListeners();
- const closers: any[] = [];
+ const closers: Array<Promise<void>> = [];
  this._closers.forEach((closerList) =>
  closerList.forEach((closer) => {
  const promise = closer();