Enable TypeScript strictNullChecks

[silverwind]

A big step towards enabling strict mode in Typescript.

There was definitely a good share of potential bugs while refactoring this. When in doubt, I opted to keep the potentially broken behaviour. Notably, the DOMEvent type is gone, it was broken and we're better of with type assertions on e.target.

[lunny]

Too many ! in the class variables, looks ugly! could we assigned anything on the constructor to avoid them? Or we can disable strictPropertyInitialization.

[silverwind]

Might be possible to move up the ! to the constructor, yes. Generally, thought there are many unavoidable ! for anything queried out of the DOM and I don't think there is a way to avoid those.

Also, I don't think we should relax any of the strict options, unless there is a clear benefit.

[wxiaoguang]

I don't think it's right to keep adding ! everywhere.

If you are refactoring, then it should follow the best practice and make the code readable / maintainable -- unless you will do quick following up changes to fix them in short time.

Just like the "jQuery removal", adding a lot ? only makes code difficult to read or maintain. At last I have to clean up them one by one to really finish the refactoring.

---

For this one, maybe the proper fix is to use useTemplateRef<T>

And a lot of other places also need a proper fix.

[silverwind]

Yes, it is better to try to ensure stuff is non-nullable in first place, I will see what I can do, but some stuff like DOM queries are unfixable without major refactors that adds ifs everywhere and I think I will defer that to later and keep the !.

[delvh]

LGTM apart from the regression

[delvh]

Suggested change

	if (!window.isSecureContext && elSignInPasskeyBtn) {
	hideElem(elSignInPasskeyBtn);
	if (!window.isSecureContext) {
	if(elSignInPasskeyBtn) hideElem(elSignInPasskeyBtn);

[delvh]

?