forked from detekt/detekt
/
SafeCast.kt
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/
SafeCast.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.ActiveByDefault
import io.gitlab.arturbosch.detekt.rules.safeAs
import org.jetbrains.kotlin.KtNodeTypes
import org.jetbrains.kotlin.psi.KtBlockExpression
import org.jetbrains.kotlin.psi.KtConstantExpression
import org.jetbrains.kotlin.psi.KtExpression
import org.jetbrains.kotlin.psi.KtIfExpression
import org.jetbrains.kotlin.psi.KtIsExpression
import org.jetbrains.kotlin.psi.KtNameReferenceExpression
/**
* This rule inspects casts and reports casts which could be replaced with safe casts instead.
*
* <noncompliant>
* fun numberMagic(number: Number) {
* val i = if (number is Int) number else null
* // ...
* }
* </noncompliant>
*
* <compliant>
* fun numberMagic(number: Number) {
* val i = number as? Int
* // ...
* }
* </compliant>
*/
@ActiveByDefault(since = "1.0.0")
class SafeCast(config: Config = Config.empty) : Rule(config) {
override val issue = Issue(
javaClass.simpleName,
Severity.Style,
"Prefer to use a safe cast instead of if-else-null.",
Debt.FIVE_MINS
)
override fun visitIfExpression(expression: KtIfExpression) {
val condition = expression.condition
if (condition is KtIsExpression) {
val leftHandSide = condition.leftHandSide
if (leftHandSide is KtNameReferenceExpression) {
val identifier = leftHandSide.text
val thenClause = expression.then
val elseClause = expression.`else`
val result = when (condition.isNegated) {
true -> isIfElseNull(elseClause, thenClause, identifier)
false -> isIfElseNull(thenClause, elseClause, identifier)
}
if (result) {
addReport(expression)
}
}
}
}
private fun isIfElseNull(thenClause: KtExpression?, elseClause: KtExpression?, identifier: String): Boolean =
thenClause.isIdentifier(identifier) && elseClause.isNullConstant()
private fun KtExpression?.isIdentifier(identifier: String): Boolean = singleExpression()?.text == identifier
private fun KtExpression?.isNullConstant(): Boolean {
val singleExpression = singleExpression() ?: return false
return singleExpression is KtConstantExpression && singleExpression.node.elementType == KtNodeTypes.NULL
}
private fun KtExpression?.singleExpression(): KtExpression? =
if (this is KtBlockExpression) children.singleOrNull()?.safeAs() else this
private fun addReport(expression: KtIfExpression) {
report(CodeSmell(issue, Entity.from(expression), "This cast should be replaced with a safe cast: as?"))
}
}