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ForbiddenVoid.kt
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ForbiddenVoid.kt
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package io.gitlab.arturbosch.detekt.rules.style
import io.gitlab.arturbosch.detekt.api.CodeSmell
import io.gitlab.arturbosch.detekt.api.Config
import io.gitlab.arturbosch.detekt.api.Debt
import io.gitlab.arturbosch.detekt.api.Entity
import io.gitlab.arturbosch.detekt.api.Issue
import io.gitlab.arturbosch.detekt.api.Rule
import io.gitlab.arturbosch.detekt.api.Severity
import io.gitlab.arturbosch.detekt.api.config
import io.gitlab.arturbosch.detekt.api.internal.ActiveByDefault
import io.gitlab.arturbosch.detekt.api.internal.Configuration
import io.gitlab.arturbosch.detekt.api.internal.RequiresTypeResolution
import io.gitlab.arturbosch.detekt.rules.fqNameOrNull
import io.gitlab.arturbosch.detekt.rules.isOverride
import org.jetbrains.kotlin.name.FqName
import org.jetbrains.kotlin.psi.KtNamedFunction
import org.jetbrains.kotlin.psi.KtParameter
import org.jetbrains.kotlin.psi.KtTypeArgumentList
import org.jetbrains.kotlin.psi.KtTypeReference
import org.jetbrains.kotlin.psi.psiUtil.anyDescendantOfType
import org.jetbrains.kotlin.psi.psiUtil.getStrictParentOfType
import org.jetbrains.kotlin.resolve.BindingContext
import org.jetbrains.kotlin.resolve.bindingContextUtil.getAbbreviatedTypeOrType
/**
* This rule detects usages of `Void` and reports them as forbidden.
* The Kotlin type `Unit` should be used instead. This type corresponds to the `Void` class in Java
* and has only one value - the `Unit` object.
*
* <noncompliant>
* runnable: () -> Void
* var aVoid: Void? = null
* </noncompliant>
*
* <compliant>
* runnable: () -> Unit
* Void::class
* </compliant>
*/
@RequiresTypeResolution
@ActiveByDefault(since = "1.21.0")
class ForbiddenVoid(config: Config = Config.empty) : Rule(config) {
override val issue = Issue(
javaClass.simpleName,
Severity.Style,
"`Unit` should be used instead of `Void`.",
Debt.FIVE_MINS
)
@Configuration("ignores void types in signatures of overridden functions")
private val ignoreOverridden: Boolean by config(false)
@Configuration("ignore void types as generic arguments")
private val ignoreUsageInGenerics: Boolean by config(false)
@Suppress("ReturnCount")
override fun visitTypeReference(typeReference: KtTypeReference) {
if (bindingContext == BindingContext.EMPTY) return
val kotlinType = typeReference.getAbbreviatedTypeOrType(bindingContext) ?: return
if (kotlinType.fqNameOrNull() == VOID_FQ_NAME) {
if (ignoreOverridden && typeReference.isPartOfOverriddenSignature()) {
return
}
if (ignoreUsageInGenerics && typeReference.isGenericArgument()) {
return
}
report(CodeSmell(issue, Entity.from(typeReference), message = "'Void' should be replaced with 'Unit'."))
}
super.visitTypeReference(typeReference)
}
private fun KtTypeReference.isPartOfOverriddenSignature() =
(isPartOfReturnTypeOfFunction() || isParameterTypeOfFunction()) &&
getStrictParentOfType<KtNamedFunction>()?.isOverride() == true
private fun KtTypeReference.isPartOfReturnTypeOfFunction() =
getStrictParentOfType<KtNamedFunction>()
?.typeReference
?.anyDescendantOfType<KtTypeReference> { it == this }
?: false
private fun KtTypeReference.isParameterTypeOfFunction() =
getStrictParentOfType<KtParameter>() != null
private fun KtTypeReference.isGenericArgument() =
getStrictParentOfType<KtTypeArgumentList>() != null
companion object {
private val VOID_FQ_NAME = FqName("java.lang.Void")
}
}