DoubleNegativeTakeUnless.kt

import io.gitlab.arturbosch.detekt.api.*
import org.jetbrains.kotlin.psi.*
import org.jetbrains.kotlin.psi.psiUtil.collectDescendantsOfType

class DoubleNegativeTakeUnless(config: Config = Config.empty) : Rule(config) {

    override val issue = Issue(
        "DoubleNegativeTakeUnless",
        Severity.Style,
        "Using double negatives with `takeUnless` can make the code harder to read.",
        Debt.FIVE_MINS
    )

    override fun visitCallExpression(expression: KtCallExpression) {
        val calleeExpression = expression.calleeExpression?.text ?: return

        if (calleeExpression == "takeUnless") {
            val lambdaExpression = expression.lambdaArguments.firstOrNull() ?: return
            val negations = lambdaExpression.collectDescendantsOfType<KtPrefixExpression> {
                it.baseExpression?.let { baseExpr ->
                    baseExpr is KtSimpleNameExpression && it.operationReference.text == "!"
                } ?: false
            }

            if (negations.isNotEmpty()) {
                report(
                    CodeSmell(
                        issue,
                        Entity.from(expression),
                        "Double negative detected with `takeUnless`. " +
                            "Consider using `takeIf` and simplifying the condition."
                    )
                )
            }
        }

        super.visitCallExpression(expression)
    }
}