Kotlin space police inspection (see https://github.com/dkandalov/live-plugin)

plugin.kts

import com.intellij.codeInspection.LocalQuickFix
import com.intellij.codeInspection.ProblemDescriptor
import com.intellij.codeInspection.ProblemHighlightType.WEAK_WARNING
import com.intellij.codeInspection.ProblemsHolder
import com.intellij.lang.ASTFactory
import com.intellij.openapi.project.Project
import com.intellij.psi.PsiElement
import com.intellij.psi.PsiElementVisitor
import com.intellij.psi.PsiWhiteSpace
import liveplugin.registerInspection
import liveplugin.show
import org.jetbrains.kotlin.idea.inspections.AbstractKotlinInspection
import org.jetbrains.kotlin.idea.util.getLineCount
import org.jetbrains.kotlin.psi.*

// depends-on-plugin org.jetbrains.kotlin

registerInspection(RedundantEmptyLinesInspection())
if (!isIdeStartup) {
    show("Loaded RedundantEmptyLinesInspection")
}

class RedundantEmptyLinesInspection : AbstractKotlinInspection() {
    override fun buildVisitor(holder: ProblemsHolder, isOnTheFly: Boolean): PsiElementVisitor {
        return object : KtVisitorVoid() {
            override fun visitWhiteSpace(space: PsiWhiteSpace) {
                val parent = space.parent
                val nextSibling = space.nextSibling
                val prevSibling = space.prevSibling
                val lineCount = space.getLineCount()

                if (lineCount >= 3 && parent is KtClassBody
                    && (prevSibling == parent.lBrace || nextSibling == parent.rBrace)
                ) return space.addTo(holder)

                if (lineCount >= 3 && parent is KtBlockExpression && parent.parent !is KtScript
                    && (prevSibling == parent.lBrace || nextSibling == parent.rBrace)
                ) return space.addTo(holder)

                if (lineCount >= 3 && parent is KtFunctionLiteral
                    && (prevSibling == parent.lBrace || prevSibling == parent.arrow || nextSibling == parent.rBrace)
                ) return space.addTo(holder)
                
                if (lineCount >= 4) return space.addTo(holder, linesToKeep = 3)
            }
        }
    }
    override fun getDisplayName() = "Redundant empty lines"
    override fun getShortName() = "Redundant empty lines"
    override fun getGroupDisplayName() = "Live Plugin"
    override fun isEnabledByDefault() = true

    private fun PsiWhiteSpace?.addTo(holder: ProblemsHolder, linesToKeep: Int = 2) {
        holder.registerProblem(
            this ?: return,
            "Redundant empty lines",
            WEAK_WARNING,
            RemoveRedundantEmptyLinesQuickFix(linesToKeep)
        )
    }

    class RemoveRedundantEmptyLinesQuickFix(private val linesToKeep: Int) : LocalQuickFix {
        override fun applyFix(project: Project, descriptor: ProblemDescriptor) {
            val node = (descriptor.psiElement as? PsiWhiteSpace)?.node ?: return
            val trimmedWhiteSpace = node.text.lineSequence().take(linesToKeep).joinToString("\n")
            node.treeParent?.replaceChild(node, ASTFactory.whitespace(trimmedWhiteSpace))
        }
        override fun getName() = "Remove redundant empty lines"
        override fun getFamilyName() = name
    }
}