The update loop occurs as a result of step 3 in which the UI updates itself from the model which then, due to a combination of developer inexperience, UI framework design/complexity, or application complexity, the UI then automatically triggers updates to the model. In my experience, this was a common defect in all applications I've seen that used various MVC style frameworks or home grown MVC architectures.
In a declarative framework, while it is still technically possible, it is very rare. The current app I'm working on is one of the largest front-end apps I've worked on (multiple years of dev). We've had a single infinite loop issue reported that was trivial to fix. We have very junior UI devs compared to teams I've worked on in the past, yet our UI defect rate is incredibly low.
> The update loop occurs as a result of step 3 in which the UI updates itself from the model which then, due to a combination of developer inexperience, UI framework design/complexity, or application complexity, the UI then automatically triggers updates to the model.
In an actual MVC framework, that can't happen.
By which I mean: it cannot and does not happen as a side effect of normal processing that you need extra skill and care to avoid.
Because updates to the UI only come from the model (but pulled by the UI when it is ready) and do nothing else. Changes to the model from the UI only come from user input and only from user input.
As an example, I can't recall every having to deal with this problem in NeXTstep/AppKit/Cocoa in the last 35 years.
If this situation is something that can and does happen just as an emergent effect of normal processing and takes extra care, effort and skill to avoid, then I would argue what you have is not a real MVC framework.
You can obviously always add bugs to programs by just putting them in manually, like, abort() or while(true) {}.
In a declarative framework, while it is still technically possible, it is very rare. The current app I'm working on is one of the largest front-end apps I've worked on (multiple years of dev). We've had a single infinite loop issue reported that was trivial to fix. We have very junior UI devs compared to teams I've worked on in the past, yet our UI defect rate is incredibly low.