2 * @fileoverview Rule to disallow a duplicate case label.
3 * @author Dieter Oberkofler
4 * @author Burak Yigit Kaya
9 //------------------------------------------------------------------------------
11 //------------------------------------------------------------------------------
13 const astUtils = require("./utils/ast-utils");
15 //------------------------------------------------------------------------------
17 //------------------------------------------------------------------------------
24 description: "disallow duplicate case labels",
25 category: "Possible Errors",
27 url: "https://eslint.org/docs/rules/no-duplicate-case"
33 unexpected: "Duplicate case label."
38 const sourceCode = context.getSourceCode();
41 * Determines whether the two given nodes are considered to be equal.
42 * @param {ASTNode} a First node.
43 * @param {ASTNode} b Second node.
44 * @returns {boolean} `true` if the nodes are considered to be equal.
46 function equal(a, b) {
47 if (a.type !== b.type) {
51 return astUtils.equalTokens(a, b, sourceCode);
54 SwitchStatement(node) {
55 const previousTests = [];
57 for (const switchCase of node.cases) {
58 if (switchCase.test) {
59 const test = switchCase.test;
61 if (previousTests.some(previousTest => equal(previousTest, test))) {
62 context.report({ node: switchCase, messageId: "unexpected" });
64 previousTests.push(test);