feat: Deno.fsEvents() (#3452)

cli/js/fs_events.ts

@@ -0,0 +1,40 @@
+// Copyright 2019 the Deno authors. All rights reserved. MIT license.
+import { sendSync, sendAsync } from "./dispatch_json.ts";
+import * as dispatch from "./dispatch.ts";
+import { close } from "./files.ts";
+
+export interface FsEvent {
+  kind: "any" | "access" | "create" | "modify" | "remove";
+  paths: string[];
+}
+
+class FsEvents implements AsyncIterableIterator<FsEvent> {
+  readonly rid: number;
+
+  constructor(paths: string[], options: { recursive: boolean }) {
+    const { recursive } = options;
+    this.rid = sendSync(dispatch.OP_FS_EVENTS_OPEN, { recursive, paths });
+  }
+
+  async next(): Promise<IteratorResult<FsEvent>> {
+    return await sendAsync(dispatch.OP_FS_EVENTS_POLL, {
+      rid: this.rid
+    });
+  }
+
+  async return(value?: FsEvent): Promise<IteratorResult<FsEvent>> {
+    close(this.rid);
+    return { value, done: true };
+  }
+
+  [Symbol.asyncIterator](): AsyncIterableIterator<FsEvent> {
+    return this;
+  }
+}
+
+export function fsEvents(
+  paths: string | string[],
+  options = { recursive: true }
+): AsyncIterableIterator<FsEvent> {
+  return new FsEvents(Array.isArray(paths) ? paths : [paths], options);
+}