UnusedPrivateMember should not report external classes/interfaces

[cortinico]

Fixes #4340

[codecov]

Codecov Report

Merging #4347 (9c30366) into main (6f41282) will increase coverage by 0.00%.
The diff coverage is 100.00%.

❗ Current head 9c30366 differs from pull request most recent head e34f95c. Consider uploading reports for the commit e34f95c to get more accurate results

@@            Coverage Diff            @@
##               main    #4347   +/-   ##
=========================================
  Coverage     84.24%   84.24%           
  Complexity     3261     3261           
=========================================
  Files           474      474           
  Lines         10325    10326    +1     
  Branches       1826     1827    +1     
=========================================
+ Hits           8698     8699    +1     
  Misses          666      666           
  Partials        961      961           

Impacted Files	Coverage Δ
...turbosch/detekt/rules/style/UnusedPrivateMember.kt	92.68% <100.00%> (+0.04%)	⬆️

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[BraisGabin]

🤔 I don't get why things that aren't private are flagged by this rule. I'm wondering if there is an underlying bug here. I mean, why this rule mixes external and private?

[cortinico]

🤔 I don't get why things that aren't private are flagged by this rule. I'm wondering if there is an underlying bug here. I mean, why this rule mixes external and private?

Yup the tests were confusing, I've fixed them. The rule is reporting private members and parameters that are unused and in my tests I accidentally removed the parameters.

[BraisGabin]

I should be missing something here... What isprivate in this snipped?

                external class Bugsnag {
                    companion object {
                        fun start(value: Int)
                        fun notify(error: String)
                    }
                }

This rule should only flag code that is marked as private right? Why was this code triggering the rule?

[cortinico]

I should be missing something here... What isprivate in this snipped?

The confusion is that UnusedPrivateMember is doing more than what its name says:

detekt/detekt-rules-style/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/UnusedPrivateMember.kt

Lines 54 to 56 in 5e34645

	* Reports unused private properties, function parameters and functions.
	* If these private elements are unused they should be removed. Otherwise, this dead code
	* can lead to confusion and potential bugs.

Ideally it should be split in UnusedFunction, UnusedParameter and UnusedPrivateMember

[BraisGabin]

I get it now! Thanks for the explanation. That have sense.