Ignore actual functions in FunctionOnlyReturningConstant (#3388)

[sczerwinski]

Closes #3388

Expected Behavior of the rule

By default, actual functions in multiplatform projects should be ignored when evaluating FunctionOnlyReturningConstant.

There should be a configuration option ignoreActualFunction, which would allow changing this behaviour.

Example

commonMain

expect class Foo {
    fun foo(param: Any): Boolean
}

jvmMain

actual class Foo {
    actual fun foo(param: Any): Boolean = checkSomeCondition(param)
}

jsMain

actual class Foo {
    actual fun foo(param: Any): Boolean = false    // <-- FunctionOnlyReturningConstant should be ignored
}

Context

Similar to ignoreOverridableFunction.

Implementing an actual function, is conceptually similar to overriding a function from an interface/abstract class.
It makes sense for such a function to provide complex logic on some platforms, and only return a constant value on others.

[codecov]

Codecov Report

Merging #3390 (c66c7f2) into master (a7efff2) will decrease coverage by 0.05%.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##             master    #3390      +/-   ##
============================================
- Coverage     80.46%   80.40%   -0.06%     
- Complexity     2739     2745       +6     
============================================
  Files           448      448              
  Lines          8282     8279       -3     
  Branches       1573     1582       +9     
============================================
- Hits           6664     6657       -7     
+ Misses          771      767       -4     
- Partials        847      855       +8     

Impacted Files	Coverage Δ	Complexity Δ
...o/gitlab/arturbosch/detekt/rules/KtModifierList.kt	100.00% <100.00%> (ø)	0.00 <0.00> (ø)
...etekt/rules/style/FunctionOnlyReturningConstant.kt	97.29% <100.00%> (+0.42%)	34.00 <10.00> (+6.00)
...t/rules/coroutines/SuspendFunWithFlowReturnType.kt	71.42% <0.00%> (-14.29%)	7.00% <0.00%> (ø%)
...n/io/gitlab/arturbosch/detekt/core/DetektResult.kt	90.00% <0.00%> (-10.00%)	7.00% <0.00%> (ø%)
...ain/kotlin/io/github/detekt/metrics/LinesOfCode.kt	93.10% <0.00%> (-6.90%)	0.00% <0.00%> (ø%)
...b/arturbosch/detekt/rules/complexity/LargeClass.kt	91.17% <0.00%> (-5.89%)	12.00% <0.00%> (ø%)
...b/arturbosch/detekt/rules/complexity/LongMethod.kt	84.09% <0.00%> (-4.55%)	16.00% <0.00%> (ø%)
...o/gitlab/arturbosch/detekt/invoke/DetektInvoker.kt	48.38% <0.00%> (-1.62%)	0.00% <0.00%> (ø%)
...n/io/github/detekt/report/sarif/RuleDescriptors.kt	20.00% <0.00%> (-1.06%)	0.00% <0.00%> (ø%)
...ain/kotlin/io/gitlab/arturbosch/detekt/api/Rule.kt	82.60% <0.00%> (ø)	16.00% <0.00%> (ø%)
... and 26 more

---

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[chao2zhang]

Thank you for fixing the glob pattern in github workflows.

[sczerwinski]

Happy to help. The difference between * and ** is well hidden in GitHub Actions documentation. Took me some time to figure out the first time.

[chao2zhang]

I learned Filter Pattern Cheat Sheet by reviewing this PR 🙏

[schalkms]

Thanks!