CognitiveComplexity: count else/else-if as one complexity

[t-kameyama]

Fixes #5447

[sanggggg]

From #5447 and paper of Cognitive Complexity,

No nesting increment is assessed for these structures because the mental cost has already been paid when reading the if.

else and else if seem to be counted as +1 complexity only (do not include nesting level increments).

[t-kameyama]

693fa8a

[sanggggg]

I'm sorry @t-kameyama, I said something that could be misunderstood.
What I'm trying to say is

else if and else

• should add +1 complexity (Increments)
• should increase nesting level (Nesting Level)
• should not add complexity by nesting level (no Nesting increments)

---

Thus, the complexity of the test code should be 39

                fun test(condition: Boolean) {
                    if (condition) { // +1
                        if (condition) { // +2
                            while(true) { // +3
                            }
                        } else if (condition) { // +1
                            while(true) { // +3
                            }
                        } else if (condition) { // +1
                            while(true) { // +3
                            }
                        } else { // +1
                            while(true) { // +3
                            }
                        }
                    } else if (condition) { // +1
                        if (condition) { // +2
                            while(true) { // +3
                            }
                        } else if (condition) // +1
                            while(true) { // +3
                            }
                    } else { // + 1
                        if (condition) { // +2
                            while(true) { // +3
                            }
                        } else // +1
                            while(true) { // +3
                            }
                    }
                    if (condition) { // +1
                    }
                }
                """
                // total 39 comple

The complexity suddenly increased, but I think this is a more real complexity (from the perspective of Cognitive Complexity)

[t-kameyama]

6b06079

[BraisGabin]

LGTM. @sanggggg it does follow what you were asking, right?

[sanggggg]

Yes, thank you for implementation! 🚀

[chao2zhang]

💯 since an else branch only increment the complexity without adding nesting