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/**
* @fileoverview Rule to disallow unnecessary labels
* @author Toru Nagashima
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("./utils/ast-utils");
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
type: "suggestion",
docs: {
description: "disallow unnecessary labels",
category: "Best Practices",
recommended: false,
url: "https://eslint.org/docs/rules/no-extra-label"
},
schema: [],
fixable: "code",
messages: {
unexpected: "This label '{{name}}' is unnecessary."
}
},
create(context) {
const sourceCode = context.getSourceCode();
let scopeInfo = null;
/**
* Creates a new scope with a breakable statement.
* @param {ASTNode} node A node to create. This is a BreakableStatement.
* @returns {void}
*/
function enterBreakableStatement(node) {
scopeInfo = {
label: node.parent.type === "LabeledStatement" ? node.parent.label : null,
breakable: true,
upper: scopeInfo
};
}
/**
* Removes the top scope of the stack.
* @returns {void}
*/
function exitBreakableStatement() {
scopeInfo = scopeInfo.upper;
}
/**
* Creates a new scope with a labeled statement.
*
* This ignores it if the body is a breakable statement.
* In this case it's handled in the `enterBreakableStatement` function.
* @param {ASTNode} node A node to create. This is a LabeledStatement.
* @returns {void}
*/
function enterLabeledStatement(node) {
if (!astUtils.isBreakableStatement(node.body)) {
scopeInfo = {
label: node.label,
breakable: false,
upper: scopeInfo
};
}
}
/**
* Removes the top scope of the stack.
*
* This ignores it if the body is a breakable statement.
* In this case it's handled in the `exitBreakableStatement` function.
* @param {ASTNode} node A node. This is a LabeledStatement.
* @returns {void}
*/
function exitLabeledStatement(node) {
if (!astUtils.isBreakableStatement(node.body)) {
scopeInfo = scopeInfo.upper;
}
}
/**
* Reports a given control node if it's unnecessary.
* @param {ASTNode} node A node. This is a BreakStatement or a
* ContinueStatement.
* @returns {void}
*/
function reportIfUnnecessary(node) {
if (!node.label) {
return;
}
const labelNode = node.label;
for (let info = scopeInfo; info !== null; info = info.upper) {
if (info.breakable || info.label && info.label.name === labelNode.name) {
if (info.breakable && info.label && info.label.name === labelNode.name) {
context.report({
node: labelNode,
messageId: "unexpected",
data: labelNode,
fix(fixer) {
const breakOrContinueToken = sourceCode.getFirstToken(node);
if (sourceCode.commentsExistBetween(breakOrContinueToken, labelNode)) {
return null;
}
return fixer.removeRange([breakOrContinueToken.range[1], labelNode.range[1]]);
}
});
}
return;
}
}
}
return {
WhileStatement: enterBreakableStatement,
"WhileStatement:exit": exitBreakableStatement,
DoWhileStatement: enterBreakableStatement,
"DoWhileStatement:exit": exitBreakableStatement,
ForStatement: enterBreakableStatement,
"ForStatement:exit": exitBreakableStatement,
ForInStatement: enterBreakableStatement,
"ForInStatement:exit": exitBreakableStatement,
ForOfStatement: enterBreakableStatement,
"ForOfStatement:exit": exitBreakableStatement,
SwitchStatement: enterBreakableStatement,
"SwitchStatement:exit": exitBreakableStatement,
LabeledStatement: enterLabeledStatement,
"LabeledStatement:exit": exitLabeledStatement,
BreakStatement: reportIfUnnecessary,
ContinueStatement: reportIfUnnecessary
};
}
};
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