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Add new rule CouldBeSequence (#4855)
* Add new rule CouldBeSequence * Add test case for CouldBeSequence * Fix inconsistency in compliant example for CoudlBeSequence
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...formance/src/main/kotlin/io/gitlab/arturbosch/detekt/rules/performance/CouldBeSequence.kt
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package io.gitlab.arturbosch.detekt.rules.performance | ||
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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.Configuration | ||
import io.gitlab.arturbosch.detekt.api.internal.RequiresTypeResolution | ||
import org.jetbrains.kotlin.name.FqName | ||
import org.jetbrains.kotlin.psi.KtCallExpression | ||
import org.jetbrains.kotlin.psi.KtExpression | ||
import org.jetbrains.kotlin.psi.psiUtil.getQualifiedExpressionForReceiver | ||
import org.jetbrains.kotlin.psi.psiUtil.getQualifiedExpressionForSelectorOrThis | ||
import org.jetbrains.kotlin.resolve.BindingContext | ||
import org.jetbrains.kotlin.resolve.calls.util.getResolvedCall | ||
import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameOrNull | ||
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/** | ||
* Long chains of collection operations will have a performance penalty due to a new list being created for each call. Consider using sequences instead. Read more about this in the [documentation](https://kotlinlang.org/docs/sequences.html) | ||
* | ||
* <noncompliant> | ||
* listOf(1, 2, 3, 4).map { it*2 }.filter { it < 4 }.map { it*it } | ||
* </noncompliant> | ||
* | ||
* <compliant> | ||
* listOf(1, 2, 3, 4).asSequence().map { it*2 }.filter { it < 4 }.map { it*it }.toList() | ||
* | ||
* listOf(1, 2, 3, 4).map { it*2 } | ||
* </compliant> | ||
*/ | ||
@RequiresTypeResolution | ||
class CouldBeSequence(config: Config = Config.empty) : Rule(config) { | ||
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override val issue: Issue = Issue( | ||
"CouldBeSequence", | ||
Severity.Performance, | ||
"Several chained collection operations that should be a sequence.", | ||
Debt.FIVE_MINS | ||
) | ||
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@Configuration("the number of chained collection operations required to trigger rule") | ||
private val threshold: Int by config(defaultValue = 3) | ||
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private var visitedCallExpressions = mutableListOf<KtExpression>() | ||
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@Suppress("ReturnCount") | ||
override fun visitCallExpression(expression: KtCallExpression) { | ||
super.visitCallExpression(expression) | ||
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if (bindingContext == BindingContext.EMPTY) return | ||
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if (visitedCallExpressions.contains(expression)) return | ||
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if (!expression.isCalling(operationsFqNames)) return | ||
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var counter = 1 | ||
var nextCall = expression.nextChainedCall() | ||
while (counter < threshold && nextCall != null) { | ||
visitedCallExpressions += nextCall | ||
if (!nextCall.isCalling(operationsFqNames)) { | ||
break | ||
} | ||
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counter++ | ||
nextCall = nextCall.nextChainedCall() | ||
} | ||
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if (counter >= threshold) { | ||
val message = "${expression.text} could be .asSequence().${expression.text}" | ||
report(CodeSmell(issue, Entity.from(expression), message)) | ||
} | ||
} | ||
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private fun KtExpression.nextChainedCall(): KtExpression? { | ||
val expression = this.getQualifiedExpressionForSelectorOrThis() | ||
return expression.getQualifiedExpressionForReceiver()?.selectorExpression | ||
} | ||
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private fun KtExpression.isCalling(fqNames: List<FqName>): Boolean { | ||
val calleeText = (this as? KtCallExpression)?.calleeExpression?.text ?: this.text | ||
val targetFqNames = fqNames.filter { it.shortName().asString() == calleeText } | ||
if (targetFqNames.isEmpty()) return false | ||
return getResolvedCall(bindingContext)?.resultingDescriptor?.fqNameOrNull() in targetFqNames | ||
} | ||
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companion object { | ||
private val operationsFqNames = listOf( | ||
FqName("kotlin.collections.filter"), | ||
FqName("kotlin.collections.filterIndexed"), | ||
FqName("kotlin.collections.map"), | ||
FqName("kotlin.collections.mapIndexed"), | ||
FqName("kotlin.collections.flatMap"), | ||
FqName("kotlin.collections.flatMapIndexed"), | ||
FqName("kotlin.collections.reduce"), | ||
FqName("kotlin.collections.zip") | ||
) | ||
} | ||
} |
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69
...ance/src/test/kotlin/io/gitlab/arturbosch/detekt/rules/performance/CouldBeSequenceSpec.kt
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package io.gitlab.arturbosch.detekt.rules.performance | ||
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import io.gitlab.arturbosch.detekt.rules.KotlinCoreEnvironmentTest | ||
import io.gitlab.arturbosch.detekt.test.TestConfig | ||
import io.gitlab.arturbosch.detekt.test.compileAndLintWithContext | ||
import org.assertj.core.api.Assertions.assertThat | ||
import org.jetbrains.kotlin.cli.jvm.compiler.KotlinCoreEnvironment | ||
import org.junit.jupiter.api.Test | ||
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@KotlinCoreEnvironmentTest | ||
class CouldBeSequenceSpec(val env: KotlinCoreEnvironment) { | ||
val subject = CouldBeSequence(TestConfig(mapOf("threshold" to 3))) | ||
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@Test | ||
fun `long collection chain should be sequence`() { | ||
val code = """ | ||
val myCollection = listOf(1, 2, 3, 4, 5, 6, 7, 8) | ||
val processed = myCollection.filter { | ||
it % 2 == 0 | ||
}.map { | ||
it*2 | ||
}.filter { | ||
it > 5 | ||
} | ||
""" | ||
assertThat(subject.compileAndLintWithContext(env, code)).hasSize(1) | ||
} | ||
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@Test | ||
fun `one collection operation should not trigger rule`() { | ||
val code = """ | ||
val myCollection = listOf(1, 2, 3, 4, 5, 6, 7, 8) | ||
val processed = myCollection.filter { | ||
it % 2 == 0 | ||
} | ||
""" | ||
assertThat(subject.compileAndLintWithContext(env, code)).isEmpty() | ||
} | ||
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@Test | ||
fun `sequence operations should not trigger rule`() { | ||
val code = """ | ||
val myCollection = listOf(1, 2, 3, 4, 5, 6, 7, 8) | ||
val processed = myCollection.asSequence().filter { | ||
it % 2 == 0 | ||
}.map { | ||
it*2 | ||
}.filter { | ||
it > 5 | ||
} | ||
""" | ||
assertThat(subject.compileAndLintWithContext(env, code)).isEmpty() | ||
} | ||
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@Test | ||
fun `sequence should not trigger rule`() { | ||
val code = """ | ||
val mySequence = sequenceOf(1,10,4,6,8,39) | ||
val processed = mySequence.filter { | ||
it % 2 == 0 | ||
}.map { | ||
it*2 | ||
}.filter { | ||
it > 5 | ||
}.toList() | ||
""" | ||
assertThat(subject.compileAndLintWithContext(env, code)).isEmpty() | ||
} | ||
} |