com.pinterest.ktlint.ruleset.standard.rules.FinalNewlineRule.kt Maven / Gradle / Ivy

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An anti-bikeshedding Kotlin linter with built-in formatter.

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package com.pinterest.ktlint.ruleset.standard.rules

import com.pinterest.ktlint.rule.engine.core.api.RuleId
import com.pinterest.ktlint.rule.engine.core.api.editorconfig.EditorConfig
import com.pinterest.ktlint.rule.engine.core.api.editorconfig.INSERT_FINAL_NEWLINE_PROPERTY
import com.pinterest.ktlint.rule.engine.core.api.isRoot
import com.pinterest.ktlint.ruleset.standard.StandardRule
import org.jetbrains.kotlin.com.intellij.lang.ASTNode
import org.jetbrains.kotlin.com.intellij.psi.PsiWhiteSpace
import org.jetbrains.kotlin.com.intellij.psi.impl.source.tree.PsiWhiteSpaceImpl

public class FinalNewlineRule :
    StandardRule(
        id = "final-newline",
        usesEditorConfigProperties = setOf(INSERT_FINAL_NEWLINE_PROPERTY),
    ) {
    private var insertFinalNewline = INSERT_FINAL_NEWLINE_PROPERTY.defaultValue

    override fun beforeFirstNode(editorConfig: EditorConfig) {
        insertFinalNewline = editorConfig[INSERT_FINAL_NEWLINE_PROPERTY]
    }

    override fun beforeVisitChildNodes(
        node: ASTNode,
        autoCorrect: Boolean,
        emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit,
    ) {
        if (node.isRoot()) {
            if (node.textLength == 0) {
                stopTraversalOfAST()
                return
            }
            val lastNode = lastChildNodeOf(node)
            if (insertFinalNewline) {
                if (lastNode !is PsiWhiteSpace || !lastNode.textContains('\n')) {
                    emit(0, "File must end with a newline (\\n)", true)
                    if (autoCorrect) {
                        node.addChild(PsiWhiteSpaceImpl("\n"), null)
                    }
                }
            } else {
                if (lastNode is PsiWhiteSpace && lastNode.textContains('\n')) {
                    emit(lastNode.startOffset, "Redundant newline (\\n) at the end of file", true)
                    if (autoCorrect) {
                        lastNode.node.treeParent.removeChild(lastNode.node)
                    }
                }
            }
        }
        stopTraversalOfAST()
    }

    private tailrec fun lastChildNodeOf(node: ASTNode): ASTNode? =
        if (node.lastChildNode == null) node else lastChildNodeOf(node.lastChildNode)
}

public val FINAL_NEWLINE_RULE_ID: RuleId = FinalNewlineRule().ruleId