> You've written a ClojureScript webapp using the Angular framework
I know this is an example but Angular is terrible with Clojurescript. Clojure has an opinionated idea of how state should change over time and that opinion does not include two-way bound attributes. The reason the cljs community is virtually all React is because dom diffing makes the UI effectively a projection from state and that is epochal-time compatible.
> How do You make sure that after changing it everything works - even the most obscure option that only one user uses?
Depends how your app is designed. In the general case where, say, you're doing the equivalent replacing Angular with Ember you just have to do it and lean on tests/QA. I have just recently finished such a refactor and it's about as fun as you're implying.
With the refactor, I have a better plan going forward! We're now on the re-frame model. All state is now in the global atom (instead of mostly being in the atom but some being component-local), dataflow is unidirectional, and we're capturing all non-determinant actions as event params. Together, it means serializing the state atom and a sequence of events allows playback on the changed code. At least in theory. I wound up having to ship rewrite delayed features and haven't taken the time to build recording/playback support.
I know this is an example but Angular is terrible with Clojurescript. Clojure has an opinionated idea of how state should change over time and that opinion does not include two-way bound attributes. The reason the cljs community is virtually all React is because dom diffing makes the UI effectively a projection from state and that is epochal-time compatible.
> How do You make sure that after changing it everything works - even the most obscure option that only one user uses?
Depends how your app is designed. In the general case where, say, you're doing the equivalent replacing Angular with Ember you just have to do it and lean on tests/QA. I have just recently finished such a refactor and it's about as fun as you're implying.
With the refactor, I have a better plan going forward! We're now on the re-frame model. All state is now in the global atom (instead of mostly being in the atom but some being component-local), dataflow is unidirectional, and we're capturing all non-determinant actions as event params. Together, it means serializing the state atom and a sequence of events allows playback on the changed code. At least in theory. I wound up having to ship rewrite delayed features and haven't taken the time to build recording/playback support.