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