Fix race condition when setting up server files

[fluiddot]

Related to #76 (comment).

Proposed Changes

• Move the call to setupWPServerFiles to the app's ready event handler. This will ensure that the setup finishes before creating the main window and let the user interact with the app.
• Add unit test to cover the case.
• Small refactor in the index.test.ts file to address issues with async code.

Testing Instructions

Note

This issue has been spotted when running E2E tests on Windows. It's unlikely that users have encountered this as it's produced by a combination of slow file disk operations and creating a site quickly after the app is launched.

• Remove all site folders to ensure that the app starts on the onboarding screen.
• Remove the folder $HOME/Library/Application Support/Studio/server-files.
• Open the app and quickly add a site.
• Observe the site is created successfully.

Pre-merge Checklist

• Have you checked for TypeScript, React or other console errors?

[fluiddot]

Seems it's not needed to wrap up this block with expect. If the function whenReady throws an exception it will make the test to fail.

cc @dcalhoun as you introduced this in #130.

[dcalhoun]

My best guess is that I wrapped it while authoring the test prior to implementing the error catching logic. Removing this makes sense.

[fluiddot]

Following Jest documentation, we should use the async version of isolateModules when there's async logic involved.

[dcalhoun]

I was unable to reproduce the referenced error in the trunk branch, but the proposed code changes LGTM. 🚀

[dcalhoun]

I suppose there is a (likely very small) possibility that the activate event fires before this promise resolves, as that event handler is adjacent to this scope. That would mean a user could still encounter the targeted error.

Seems like a very unlikely scenario that we do not need to address, but I share it nonetheless.

studio/src/index.ts

Lines 251 to 257 in 4aa60ff

	app.on( 'activate', () => {
	// On OS X it's common to re-create a window in the app when the
	// dock icon is clicked and there are no other windows open.
	if ( BrowserWindow.getAllWindows().length === 0 ) {
	app.whenReady().then( createMainWindow ).catch( Sentry.captureException );
	}
	} );

[fluiddot]

Yeah, I think that would probably be an edge case. I tested adding a delay when executing the ready event, and triggering the ready event by cliking on the dock icon of the Studio app results in an exception. This could be easily addressed by adding a condition in activate event to only create the main window when all the logic performed in ready is complete. I'll do this in a different PR.

Error:

Error occurred in handler for 'getAppGlobals': Error: No handler registered for 'getAppGlobals'
    at WebContents.<anonymous> (node:electron/js2c/browser_init:2:78277)
    at WebContents.emit (node:events:514:28)
    at WebContents.emit (node:domain:488:12)

[fluiddot]

I came to realize this might be more common than we expect based on the issue Automattic/dotcom-forge#8016. I'll try to tackle it asap.

[dcalhoun]

My best guess is that I wrapped it while authoring the test prior to implementing the error catching logic. Removing this makes sense.