77 lines
1.8 KiB
JavaScript
77 lines
1.8 KiB
JavaScript
/**
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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('../types').Rule.RuleModule} */
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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 (
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tokensA.length === tokensB.length &&
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tokensA.every(
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(token, index) =>
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token.type === tokensB[index].type &&
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token.value === tokensB[index].value
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)
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);
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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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'===',
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'==',
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'!==',
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'!=',
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'>',
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'<',
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'>=',
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'<=',
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]);
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if (
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operators.has(node.operator) &&
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hasSameTokens(node.left, node.right)
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) {
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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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