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| /** | |
| * @fileoverview Rule to disallow unused labels. | |
| * @author Toru Nagashima | |
| */ | |
| "use strict"; | |
| //------------------------------------------------------------------------------ | |
| // Rule Definition | |
| //------------------------------------------------------------------------------ | |
| module.exports = { | |
| meta: { | |
| type: "suggestion", | |
| docs: { | |
| description: "disallow unused labels", | |
| category: "Best Practices", | |
| recommended: true, | |
| url: "https://eslint.org/docs/rules/no-unused-labels" | |
| }, | |
| schema: [], | |
| fixable: "code", | |
| messages: { | |
| unused: "'{{name}}:' is defined but never used." | |
| } | |
| }, | |
| create(context) { | |
| const sourceCode = context.getSourceCode(); | |
| let scopeInfo = null; | |
| /** | |
| * Adds a scope info to the stack. | |
| * @param {ASTNode} node A node to add. This is a LabeledStatement. | |
| * @returns {void} | |
| */ | |
| function enterLabeledScope(node) { | |
| scopeInfo = { | |
| label: node.label.name, | |
| used: false, | |
| upper: scopeInfo | |
| }; | |
| } | |
| /** | |
| * Removes the top of the stack. | |
| * At the same time, this reports the label if it's never used. | |
| * @param {ASTNode} node A node to report. This is a LabeledStatement. | |
| * @returns {void} | |
| */ | |
| function exitLabeledScope(node) { | |
| if (!scopeInfo.used) { | |
| context.report({ | |
| node: node.label, | |
| messageId: "unused", | |
| data: node.label, | |
| fix(fixer) { | |
| /* | |
| * Only perform a fix if there are no comments between the label and the body. This will be the case | |
| * when there is exactly one token/comment (the ":") between the label and the body. | |
| */ | |
| if (sourceCode.getTokenAfter(node.label, { includeComments: true }) === | |
| sourceCode.getTokenBefore(node.body, { includeComments: true })) { | |
| return fixer.removeRange([node.range[0], node.body.range[0]]); | |
| } | |
| return null; | |
| } | |
| }); | |
| } | |
| scopeInfo = scopeInfo.upper; | |
| } | |
| /** | |
| * Marks the label of a given node as used. | |
| * @param {ASTNode} node A node to mark. This is a BreakStatement or | |
| * ContinueStatement. | |
| * @returns {void} | |
| */ | |
| function markAsUsed(node) { | |
| if (!node.label) { | |
| return; | |
| } | |
| const label = node.label.name; | |
| let info = scopeInfo; | |
| while (info) { | |
| if (info.label === label) { | |
| info.used = true; | |
| break; | |
| } | |
| info = info.upper; | |
| } | |
| } | |
| return { | |
| LabeledStatement: enterLabeledScope, | |
| "LabeledStatement:exit": exitLabeledScope, | |
| BreakStatement: markAsUsed, | |
| ContinueStatement: markAsUsed | |
| }; | |
| } | |
| }; |