refactor: use sets instead of lists for stashing circular references (DEV-2771)

[BalduinLandolt]

No description provided.

[linear]

DEV-2771 use sets instead of lists for stashing circular references

[jnussbaum]

I didn't look closely at the algorithm, I just trust you :-)

[BalduinLandolt]

I didn't look closely at the algorithm, I just trust you :-)

sounds risky! xD

[Nora-Olivia-Ammann]

Looks good to me.
What is the advantage to switch to sets in this case?

[BalduinLandolt]

Looks good to me. What is the advantage to switch to sets in this case?

In this case an insignificant performance increase (if x in y: ... is considerably faster with sets, and that happens a lot here; but this is not the slow part of the code, so it doesn't matter.)
But mostly I can do isSubsetOf() which does away with having to check for each link, if it is in the ok set. This could be done with all(...) too, but less nicely. And this allowed me to get rid of the ok boolean which made the whole loop ugly and caused an extra step of if-nesting.

But this was mostly about getting a PR merged to warm up with the repo; and only marginally to make it easier to change stuff in a later step.