95 lines
2.9 KiB
JavaScript
95 lines
2.9 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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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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category: "Stylistic Issues",
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recommended: false,
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url: "https://eslint.org/docs/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 test.type === "BinaryExpression" &&
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(test.operator === "!=" || test.operator === "!==");
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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 isNegatedUnaryExpression(node.test) || isNegatedBinaryExpression(node.test);
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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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