forked from detekt/detekt
/
UseSumOfInsteadOfFlatMapSize.kt
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/
UseSumOfInsteadOfFlatMapSize.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.internal.RequiresTypeResolution
import io.gitlab.arturbosch.detekt.rules.isCalling
import io.gitlab.arturbosch.detekt.rules.safeAs
import org.jetbrains.kotlin.builtins.DefaultBuiltIns
import org.jetbrains.kotlin.descriptors.ClassDescriptor
import org.jetbrains.kotlin.name.FqName
import org.jetbrains.kotlin.psi.KtCallExpression
import org.jetbrains.kotlin.psi.KtExpression
import org.jetbrains.kotlin.psi.KtNameReferenceExpression
import org.jetbrains.kotlin.psi.psiUtil.getQualifiedExpressionForReceiver
import org.jetbrains.kotlin.psi.psiUtil.getQualifiedExpressionForSelectorOrThis
import org.jetbrains.kotlin.resolve.calls.util.getType
import org.jetbrains.kotlin.resolve.descriptorUtil.isSubclassOf
/**
* Turn on this rule to flag `flatMap` and `size/count` calls that can be replaced with a `sumOf` call.
*
* <noncompliant>
* class Foo(val foo: List<Int>)
* list.flatMap { it.foo }.size
* list.flatMap { it.foo }.count()
* list.flatMap { it.foo }.count { it > 2 }
* listOf(listOf(1), listOf(2, 3)).flatten().size
* </noncompliant>
*
* <compliant>
* list.sumOf { it.foo.size }
* list.sumOf { it.foo.count() }
* list.sumOf { it.foo.count { foo -> foo > 2 } }
* listOf(listOf(1), listOf(2, 3)).sumOf { it.size }
* </compliant>
*/
@RequiresTypeResolution
class UseSumOfInsteadOfFlatMapSize(config: Config = Config.empty) : Rule(config) {
override val issue: Issue = Issue(
javaClass.simpleName,
Severity.Style,
"Use `sumOf` instead of `flatMap` and `size/count` calls",
Debt.FIVE_MINS
)
@Suppress("ReturnCount")
override fun visitCallExpression(expression: KtCallExpression) {
super.visitCallExpression(expression)
val calleeText = expression.calleeExpression?.text ?: return
if (!expression.isFlatMapOrFlatten()) return
val receiver = expression.getQualifiedExpressionForSelectorOrThis()
val selector = receiver.getQualifiedExpressionForReceiver()?.selectorExpression ?: return
if (!selector.isSizeOrCount(receiver)) return
val selectorText = selector.safeAs<KtCallExpression>()?.calleeExpression?.text ?: selector.text
val message = "Use 'sumOf' instead of '$calleeText' and '$selectorText'"
report(CodeSmell(issue, Entity.from(expression), message))
}
private fun KtCallExpression.isFlatMapOrFlatten(): Boolean = isCalling(flatMapAndFlattenFqName, bindingContext)
@Suppress("ReturnCount")
private fun KtExpression.isSizeOrCount(receiver: KtExpression): Boolean {
if (safeAs<KtNameReferenceExpression>()?.text == "size") {
val receiverType = receiver.getType(bindingContext) ?: return false
val descriptor = receiverType.constructor.declarationDescriptor?.safeAs<ClassDescriptor>() ?: return false
return descriptor.isSubclassOf(DefaultBuiltIns.Instance.list)
}
return safeAs<KtCallExpression>()?.isCalling(countFqName, bindingContext) == true
}
companion object {
private val flatMapAndFlattenFqName = listOf(
FqName("kotlin.collections.flatMap"),
FqName("kotlin.collections.flatten"),
)
private val countFqName = FqName("kotlin.collections.count")
}
}