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[OptionalUnit] Allow a function to declare a Unit return type when it uses a generic function initializer #4371

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merged 7 commits into from Dec 15, 2021
Merged

[OptionalUnit] Allow a function to declare a Unit return type when it uses a generic function initializer #4371

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b11c357
Allow a function to declare a Unit return type when it uses a generic…
severn-everett Dec 12, 2021
1489248
Added check for when redundant function return typing and generic typ…
severn-everett Dec 12, 2021
b0bd724
Added test to expand code coverage
severn-everett Dec 12, 2021
a96f4a0
Optimizing check for whether a function contains an initializer
severn-everett Dec 12, 2021
4e15b13
Adding more tests to improve code coverage
severn-everett Dec 12, 2021
71ffd13
Adding another test to improve code coverage
severn-everett Dec 13, 2021
cc5c1f2
Removing test due to it failing compilation check
severn-everett Dec 13, 2021
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13 changes: 10 additions & 3 deletions ...es-style/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/style/optional/OptionalUnit.kt
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Expand Up @@ -9,6 +9,7 @@ import io.gitlab.arturbosch.detekt.api.Rule
import io.gitlab.arturbosch.detekt.api.Severity
import io.gitlab.arturbosch.detekt.rules.isOverride
import org.jetbrains.kotlin.cfg.WhenChecker
import org.jetbrains.kotlin.js.translate.callTranslator.getReturnType
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No idea why this is in a JavaScript package, but it appears to work in JVM code.

import org.jetbrains.kotlin.psi.KtBlockExpression
import org.jetbrains.kotlin.psi.KtExpression
import org.jetbrains.kotlin.psi.KtIfExpression
Expand All @@ -18,8 +19,10 @@ import org.jetbrains.kotlin.psi.KtWhenExpression
import org.jetbrains.kotlin.psi.psiUtil.siblings
import org.jetbrains.kotlin.resolve.BindingContext
import org.jetbrains.kotlin.resolve.bindingContextUtil.isUsedAsExpression
import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
import org.jetbrains.kotlin.resolve.calls.callUtil.getType
import org.jetbrains.kotlin.types.typeUtil.isNothing
import org.jetbrains.kotlin.types.typeUtil.isTypeParameter
import org.jetbrains.kotlin.types.typeUtil.isUnit
import org.jetbrains.kotlin.utils.addToStdlib.firstIsInstanceOrNull

Expand Down Expand Up @@ -109,7 +112,7 @@ class OptionalUnit(config: Config = Config.empty) : Rule(config) {
val typeReference = function.typeReference
val typeElementText = typeReference?.typeElement?.text
if (typeElementText == UNIT) {
if (function.initializer.isNothingType()) return
if (function.initializer.isGenericOrNothingType()) return
report(CodeSmell(issue, Entity.from(typeReference), createMessage(function)))
}
}
Expand All @@ -124,8 +127,12 @@ class OptionalUnit(config: Config = Config.empty) : Rule(config) {
private fun createMessage(function: KtNamedFunction) = "The function ${function.name} " +
"defines a return type of Unit. This is unnecessary and can safely be removed."

private fun KtExpression?.isNothingType() =
bindingContext != BindingContext.EMPTY && this?.getType(bindingContext)?.isNothing() == true
private fun KtExpression?.isGenericOrNothingType(): Boolean {
if (bindingContext == BindingContext.EMPTY) return false
val isGenericType = this?.getResolvedCall(bindingContext)?.getReturnType()?.isTypeParameter() == true
val isNothingType = this?.getType(bindingContext)?.isNothing() == true
return isGenericType || isNothingType
}

companion object {
private const val UNIT = "Unit"
Expand Down
14 changes: 14 additions & 0 deletions ...tyle/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/style/optional/OptionalUnitSpec.kt
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Expand Up @@ -305,5 +305,19 @@ class OptionalUnitSpec : Spek({
val findings = subject.compileAndLintWithContext(env, code)
assertThat(findings).isEmpty()
}

it("should not report when the function initializer requires a type") {
val code = """
fun <T> foo(block: (List<T>) -> Unit): T {
val list = listOf<T>()
block(list)
return list.first()
}

fun doFoo(): Unit = foo {}
""".trimIndent()
val findings = subject.compileAndLintWithContext(env, code)
assertThat(findings).isEmpty()
}
}
})