setFileHandler blocks webui.js from being served

[DevRubicate]

I'm trying to use setFileHandler to serve a .js file for a <script src="test.js"> in my WebUI window.

Scenario 1:

const win = new WebUI();
win.show(myhtml);
win.setFileHandler(myCallback);

Outcome:
The window opens and attempts to load test.js before setFileHandler starts serving, leading to a 404.

Scenario 2:

const win = new WebUI();
win.setFileHandler(myCallback);
win.show(myhtml);

Outcome:
The window opens and during it's initialization where it needs to load the built-in webui.js then setFileHandler blocks that requests and does not serve webui.js so the window never successfully initializes.

I suggest that setFileHandler be changed to have a hardcoded exception for webui.js so that it will not intercept that request and allow the window initialization proceed as normal. It's possible that the same happens with favicon.svg but I have not tested.

Edit: I tried serving a copy of webui.js myself in setFileHandler but the window still fails to initialize, so my diagnosis might not be 100% accurate. I can at least confirm that loading test.js inside a setTimeout so that there is a delay makes it successfully load from setFileHandler

[AlbertShown]

I suggest that setFileHandler be changed to have a hardcoded exception for webui.js

It should be already the case, let me check that.