io.gitlab.arturbosch.detekt.rules.style.UseEmptyCounterpart.kt Maven / Gradle / Ivy

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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 org.jetbrains.kotlin.name.FqName
import org.jetbrains.kotlin.psi.KtCallExpression
import org.jetbrains.kotlin.resolve.calls.callUtil.getResolvedCall
import org.jetbrains.kotlin.resolve.descriptorUtil.fqNameOrNull

/**
 * Instantiation of an object's "empty" state should use the object's "empty" initializer for clarity purposes.
 *
 * 
 * arrayOf()
 * listOf() // or listOfNotNull()
 * mapOf()
 * sequenceOf()
 * setOf()
 * 
 *
 * 
 * emptyArray()
 * emptyList()
 * emptyMap()
 * emptySequence()
 * emptySet()
 * 
 *
 */
@RequiresTypeResolution
class UseEmptyCounterpart(config: Config) : Rule(config) {

    override val issue = Issue(
        javaClass.simpleName,
        Severity.Style,
        """Instantiation of an object's "empty" state should use the object's "empty" initializer""",
        Debt.FIVE_MINS
    )

    @Suppress("ReturnCount")
    override fun visitCallExpression(expression: KtCallExpression) {
        super.visitCallExpression(expression)

        val resolvedCall = expression.getResolvedCall(bindingContext) ?: return
        val fqName = resolvedCall.resultingDescriptor.fqNameOrNull() ?: return
        val emptyCounterpart = exprsWithEmptyCounterparts[fqName] ?: return

        if (expression.valueArguments.isEmpty()) {
            val message = "${fqName.shortName()} can be replaced with $emptyCounterpart"
            report(CodeSmell(issue, Entity.from(expression), message))
        }
    }
}

private val exprsWithEmptyCounterparts = mapOf(
    FqName("kotlin.arrayOf") to "emptyArray",
    FqName("kotlin.collections.listOf") to "emptyList",
    FqName("kotlin.collections.listOfNotNull") to "emptyList",
    FqName("kotlin.collections.mapOf") to "emptyMap",
    FqName("kotlin.sequences.sequenceOf") to "emptySequence",
    FqName("kotlin.collections.setOf") to "emptySet"
)