Flipper export file implementation

Summary:
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Changelog: add export file implementation for browsers

Reviewed By: antonk52

Differential Revision: D46840341

fbshipit-source-id: 8a011f2a7c0ce329286cb8813def8f9c0572d133

desktop/flipper-ui-browser/package.json

@@ -10,9 +10,11 @@
   "license": "MIT",
   "bugs": "https://github.com/facebook/flipper/issues",
   "dependencies": {
+    "file-saver": "^2.0.5",
     "reconnecting-websocket": "^4.4.0"
   },
   "devDependencies": {
+    "@types/file-saver": "^2.0.5",
     "eventemitter3": "^4.0.7",
     "flipper-common": "0.0.0",
     "flipper-frontend-core": "0.0.0",

desktop/flipper-ui-browser/src/initializeRenderHost.tsx

@@ -14,6 +14,7 @@ import {
   wrapRequire,
 } from 'flipper-common';
 import type {RenderHost} from 'flipper-ui-core';
+import FileSaver from 'file-saver';
 
 declare module globalThis {
   let require: any;
@@ -44,11 +45,22 @@ export function initializeRenderHost(
     async importFile() {
       throw new Error('Not implemented');
     },
-    async exportFile() {
-      throw new Error('Not implemented');
+    async exportFile(data: string, {defaultPath}: {defaultPath?: string}) {
+      const file = new File([data], defaultPath ?? 'unknown', {
+        type: 'text/plain;charset=utf-8',
+      });
+      FileSaver.saveAs(file);
+      return defaultPath;
     },
-    async exportFileBinary() {
-      throw new Error('Not implemented');
+    async exportFileBinary(
+      data: Uint8Array,
+      {defaultPath}: {defaultPath?: string},
+    ) {
+      const file = new File([data], defaultPath ?? 'unknown', {
+        type: 'application/octet-stream',
+      });
+      FileSaver.saveAs(file);
+      return defaultPath;
     },
     openLink(url: string) {
       window.open(url, '_blank');