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| /** | |
| * @fileoverview Rule to flag comparison where left part is the same as the right | |
| * part. | |
| * @author Ilya Volodin | |
| */ | |
| "use strict"; | |
| //------------------------------------------------------------------------------ | |
| // Rule Definition | |
| //------------------------------------------------------------------------------ | |
| module.exports = { | |
| meta: { | |
| type: "problem", | |
| docs: { | |
| description: "disallow comparisons where both sides are exactly the same", | |
| category: "Best Practices", | |
| recommended: false, | |
| url: "https://eslint.org/docs/rules/no-self-compare" | |
| }, | |
| schema: [] | |
| }, | |
| create(context) { | |
| const sourceCode = context.getSourceCode(); | |
| /** | |
| * Determines whether two nodes are composed of the same tokens. | |
| * @param {ASTNode} nodeA The first node | |
| * @param {ASTNode} nodeB The second node | |
| * @returns {boolean} true if the nodes have identical token representations | |
| */ | |
| function hasSameTokens(nodeA, nodeB) { | |
| const tokensA = sourceCode.getTokens(nodeA); | |
| const tokensB = sourceCode.getTokens(nodeB); | |
| return tokensA.length === tokensB.length && | |
| tokensA.every((token, index) => token.type === tokensB[index].type && token.value === tokensB[index].value); | |
| } | |
| return { | |
| BinaryExpression(node) { | |
| const operators = new Set(["===", "==", "!==", "!=", ">", "<", ">=", "<="]); | |
| if (operators.has(node.operator) && hasSameTokens(node.left, node.right)) { | |
| context.report({ node, message: "Comparing to itself is potentially pointless." }); | |
| } | |
| } | |
| }; | |
| } | |
| }; |