core: routing - navigateToPrevious() stays on the current state if last state was navigated twice (dynamic params)

[christophercr]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[X] Bug report  
[ ] Feature request
[ ] Documentation issue or request
[ ] Support request => Please do not submit support request here, instead see https://github.com/NationalBankBelgium/stark/blob/master/CONTRIBUTING.md#got-a-question-or-problem

Current behavior

After navigating two or more times to the same current state in order to change the state parameters (dynamic transition), every single transition is kept in the Routing Service state history as a different transition. Then, calling the navigatToPrevious() once will not navigate to the previous page but to the previous transition of the current state, meaning that the navigateToPrevious() should be called as many times as dynamic transitions were made.

Expected behavior

Calling navigateToPrevious() once should navigate to the previous page regardless of whether the previous transition(s) where dynamic or not.

Minimal reproduction of the problem with instructions

1. Define two states A & B, state B has a dynamic parameter
2. Navigate to state A
   -- _starkStateHistory = [A]
3. Navigate to state B
   -- _starkStateHistory = [A, B]
4. Update B's dynamic parameter (by using navigateTo())
   -- _starkStateHistory = [A, B, B]
5. Call navigateToPrevious()
   -- service tries to navigate to B instead of A, a second call to navigateToPrevious() will go back to state A

What is the motivation / use case for changing the behavior?

Consistent "navigate to previous" functionality.

Environment

Angular version: 6.1.8
Stark version: 10.0.0-beta.0