Add missing return to FileStorage.write

[ravicious]

Ever since we switched to Vite and started using electron-vite to automatically restart the Electron app on changes in dev mode, I sometimes noticed my app_state.json getting corrupted and the app starting in a pristine state, showing modals as if it was launched for the first time.

I attributed this to app_state.json getting corrupted. I looked for a relevant error in my logs and sure enough there it was:

[23-05-24 10:35:16] [FileStorage] error: Cannot read /Users/rav/Library/Application Support/Electron/app_state.json file SyntaxError: Unexpected end of JSON input
    at JSON.parse (<anonymous>)
    at loadStateSync (/Users/rav/src/teleport/web/packages/teleterm/build/app/main/index.js:909:15)
    at createFileStorage (/Users/rav/src/teleport/web/packages/teleterm/build/app/main/index.js:857:13)
    at createFileStorages (/Users/rav/src/teleport/web/packages/teleterm/build/app/main/index.js:75420:26)
    at initializeApp (/Users/rav/src/teleport/web/packages/teleterm/build/app/main/index.js:75246:7)

I suspected that it might be due to electron-vite sending a sigkill to the Electron app and the app getting killed while it's writing to the file. I asked Grzegorz if he ever ran into that, and he confirmed that he did run into that too.

Grzegorz said, "I wonder if changing appStateFileStorage.write() to a sync write instead of async-based one would help here", and I said, "I don't think so, it's already awaited for…"

teleport/web/packages/teleterm/src/main.ts

Lines 119 to 132 in c7d2830

	app.on('will-quit', async event => {
	event.preventDefault();
	const disposeMainProcess = async () => {
	try {
	await mainProcess.dispose();
	} catch (e) {
	logger.error('Failed to gracefully dispose of main process', e);
	}
	};
	globalShortcut.unregisterAll();
	await Promise.all([appStateFileStorage.write(), disposeMainProcess()]); // none of them can throw
	app.exit();
	});

Well, turns out it wasn't, because we failed to return a promise from FileStorage.write! This is one of the things that no-floating-promises would have caught (#41945).

[public-teleport-github-review-bot]

@ravicious See the table below for backport results.

Branch	Result
branch/v13	Create PR
branch/v14	Create PR
branch/v15	Create PR