101 lines
2.6 KiB
JavaScript
101 lines
2.6 KiB
JavaScript
/**
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* @fileoverview Rule to disallow a negated condition
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* @author Alberto Rodríguez
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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: 'suggestion',
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docs: {
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description: 'Disallow negated conditions',
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recommended: false,
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frozen: true,
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url: 'https://eslint.org/docs/latest/rules/no-negated-condition',
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},
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schema: [],
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messages: {
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unexpectedNegated: 'Unexpected negated condition.',
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},
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},
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create(context) {
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/**
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* Determines if a given node is an if-else without a condition on the else
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* @param {ASTNode} node The node to check.
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* @returns {boolean} True if the node has an else without an if.
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* @private
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*/
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function hasElseWithoutCondition(node) {
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return node.alternate && node.alternate.type !== 'IfStatement';
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}
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/**
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* Determines if a given node is a negated unary expression
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* @param {Object} test The test object to check.
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* @returns {boolean} True if the node is a negated unary expression.
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* @private
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*/
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function isNegatedUnaryExpression(test) {
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return test.type === 'UnaryExpression' && test.operator === '!';
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}
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/**
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* Determines if a given node is a negated binary expression
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* @param {Test} test The test to check.
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* @returns {boolean} True if the node is a negated binary expression.
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* @private
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*/
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function isNegatedBinaryExpression(test) {
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return (
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test.type === 'BinaryExpression' &&
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(test.operator === '!=' || test.operator === '!==')
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);
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}
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/**
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* Determines if a given node has a negated if expression
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* @param {ASTNode} node The node to check.
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* @returns {boolean} True if the node has a negated if expression.
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* @private
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*/
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function isNegatedIf(node) {
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return (
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isNegatedUnaryExpression(node.test) ||
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isNegatedBinaryExpression(node.test)
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);
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}
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return {
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IfStatement(node) {
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if (!hasElseWithoutCondition(node)) {
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return;
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}
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if (isNegatedIf(node)) {
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context.report({
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node,
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messageId: 'unexpectedNegated',
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});
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}
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},
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ConditionalExpression(node) {
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if (isNegatedIf(node)) {
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context.report({
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node,
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messageId: 'unexpectedNegated',
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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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