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NoTrailingCommaRule.kt
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NoTrailingCommaRule.kt
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package com.pinterest.ktlint.ruleset.experimental
import com.pinterest.ktlint.core.Rule
import com.pinterest.ktlint.core.ast.ElementType
import com.pinterest.ktlint.core.ast.assertElementType
import com.pinterest.ktlint.core.ast.children
import com.pinterest.ktlint.core.ast.prevLeaf
import org.jetbrains.kotlin.com.intellij.lang.ASTNode
import org.jetbrains.kotlin.psi.psiUtil.endOffset
class NoTrailingCommaRule : Rule("no-trailing-comma") {
override fun visit(
node: ASTNode,
autoCorrect: Boolean,
emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit
) {
when (node.elementType) {
ElementType.COLLECTION_LITERAL_EXPRESSION ->
// TODO: According to https://github.com/JetBrains/intellij-kotlin/blob/master/formatter/src/org/jetbrains/kotlin/idea/formatter/trailingComma/util.kt
// it is possible to have a trailing comma with this type of element. Need an example before it can
// be implemented
Unit
ElementType.DESTRUCTURING_DECLARATION -> visitDestructuringDeclaration(node, emit, autoCorrect)
ElementType.FUNCTION_LITERAL -> visitFunctionLiteral(node, emit, autoCorrect)
ElementType.FUNCTION_TYPE -> visitFunctionType(node, emit, autoCorrect)
ElementType.INDICES -> visitIndices(node, emit, autoCorrect)
ElementType.TYPE_ARGUMENT_LIST -> visitTypeList(node, emit, autoCorrect)
ElementType.TYPE_PARAMETER_LIST -> visitTypeList(node, emit, autoCorrect)
ElementType.VALUE_ARGUMENT_LIST -> visitValueList(node, emit, autoCorrect)
ElementType.VALUE_PARAMETER_LIST -> visitValueList(node, emit, autoCorrect)
ElementType.WHEN_ENTRY -> visitWhenEntry(node, emit, autoCorrect)
else -> Unit
}
}
private fun visitDestructuringDeclaration(
node: ASTNode,
emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit,
autoCorrect: Boolean
) {
val inspectNode = node
.assertElementType(ElementType.DESTRUCTURING_DECLARATION)
.children()
.last { it.elementType == ElementType.RPAR }
.prevLeaf()
node.reportAndOrCorrectTrailingCommaNodeBefore(inspectNode, emit, autoCorrect)
}
private fun visitFunctionLiteral(
node: ASTNode,
emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit,
autoCorrect: Boolean
) {
val inspectNode = node
.assertElementType(ElementType.FUNCTION_LITERAL)
.children()
.lastOrNull() { it.elementType == ElementType.ARROW }
?.prevLeaf()
node.reportAndOrCorrectTrailingCommaNodeBefore(inspectNode, emit, autoCorrect)
}
private fun visitFunctionType(
node: ASTNode,
emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit,
autoCorrect: Boolean
) {
val inspectNode = node
.assertElementType(ElementType.FUNCTION_TYPE)
.firstChildNode
.assertElementType(ElementType.VALUE_PARAMETER_LIST)
.children()
.last()
.prevLeaf()
node.reportAndOrCorrectTrailingCommaNodeBefore(inspectNode, emit, autoCorrect)
}
private fun visitIndices(
node: ASTNode,
emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit,
autoCorrect: Boolean
) {
val inspectNode = node
.assertElementType(ElementType.INDICES)
.children()
.last { it.elementType == ElementType.RBRACKET }
.prevLeaf()
node.reportAndOrCorrectTrailingCommaNodeBefore(inspectNode, emit, autoCorrect)
}
private fun visitValueList(
node: ASTNode,
emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit,
autoCorrect: Boolean
) {
if (node.treeParent.elementType != ElementType.FUNCTION_LITERAL &&
node.treeParent.elementType != ElementType.FUNCTION_TYPE
) {
val inspectNode = node
.assertElementType(ElementType.VALUE_ARGUMENT_LIST, ElementType.VALUE_PARAMETER_LIST)
.children()
.last { it.elementType == ElementType.RPAR }
.prevLeaf()
node.reportAndOrCorrectTrailingCommaNodeBefore(inspectNode, emit, autoCorrect)
}
}
private fun visitTypeList(
node: ASTNode,
emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit,
autoCorrect: Boolean
) {
val inspectNode = node
.assertElementType(ElementType.TYPE_ARGUMENT_LIST, ElementType.TYPE_PARAMETER_LIST)
.children()
.first { it.elementType == ElementType.GT }
.prevLeaf()
node.reportAndOrCorrectTrailingCommaNodeBefore(inspectNode, emit, autoCorrect)
}
private fun visitWhenEntry(
node: ASTNode,
emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit,
autoCorrect: Boolean
) {
val inspectNode = node
.assertElementType(ElementType.WHEN_ENTRY)
.children()
.first { it.elementType == ElementType.ARROW }
.prevLeaf()
node.reportAndOrCorrectTrailingCommaNodeBefore(inspectNode, emit, autoCorrect)
}
private fun ASTNode.reportAndOrCorrectTrailingCommaNodeBefore(
inspectNode: ASTNode?,
emit: (offset: Int, errorMessage: String, canBeAutoCorrected: Boolean) -> Unit,
autoCorrect: Boolean
) {
inspectNode
.findPreviousTrailingCommaNodeOrNull()
?.let { trailingCommaNode ->
emit(trailingCommaNode.psi.endOffset - 1, "Trailing comma is redundant", true)
if (autoCorrect) {
this.removeChild(trailingCommaNode)
}
}
}
private fun ASTNode?.findPreviousTrailingCommaNodeOrNull(): ASTNode? {
var node = this
while (node != null && node.isIgnorable()) {
node = node.prevLeaf()
}
return if (node != null && node.elementType == ElementType.COMMA) {
node
} else {
null
}
}
private fun ASTNode.isIgnorable(): Boolean =
elementType == ElementType.WHITE_SPACE ||
elementType == ElementType.EOL_COMMENT ||
elementType == ElementType.BLOCK_COMMENT
}