| /** |
| * @fileoverview Rule to disallow a negated condition |
| * @author Alberto RodrÃguez |
| */ |
| "use strict"; |
| |
| //------------------------------------------------------------------------------ |
| // Rule Definition |
| //------------------------------------------------------------------------------ |
| |
| module.exports = { |
| meta: { |
| type: "suggestion", |
| |
| docs: { |
| description: "disallow negated conditions", |
| category: "Stylistic Issues", |
| recommended: false, |
| url: "https://eslint.org/docs/rules/no-negated-condition" |
| }, |
| |
| schema: [] |
| }, |
| |
| create(context) { |
| |
| /** |
| * Determines if a given node is an if-else without a condition on the else |
| * @param {ASTNode} node The node to check. |
| * @returns {boolean} True if the node has an else without an if. |
| * @private |
| */ |
| function hasElseWithoutCondition(node) { |
| return node.alternate && node.alternate.type !== "IfStatement"; |
| } |
| |
| /** |
| * Determines if a given node is a negated unary expression |
| * @param {Object} test The test object to check. |
| * @returns {boolean} True if the node is a negated unary expression. |
| * @private |
| */ |
| function isNegatedUnaryExpression(test) { |
| return test.type === "UnaryExpression" && test.operator === "!"; |
| } |
| |
| /** |
| * Determines if a given node is a negated binary expression |
| * @param {Test} test The test to check. |
| * @returns {boolean} True if the node is a negated binary expression. |
| * @private |
| */ |
| function isNegatedBinaryExpression(test) { |
| return test.type === "BinaryExpression" && |
| (test.operator === "!=" || test.operator === "!=="); |
| } |
| |
| /** |
| * Determines if a given node has a negated if expression |
| * @param {ASTNode} node The node to check. |
| * @returns {boolean} True if the node has a negated if expression. |
| * @private |
| */ |
| function isNegatedIf(node) { |
| return isNegatedUnaryExpression(node.test) || isNegatedBinaryExpression(node.test); |
| } |
| |
| return { |
| IfStatement(node) { |
| if (!hasElseWithoutCondition(node)) { |
| return; |
| } |
| |
| if (isNegatedIf(node)) { |
| context.report({ node, message: "Unexpected negated condition." }); |
| } |
| }, |
| ConditionalExpression(node) { |
| if (isNegatedIf(node)) { |
| context.report({ node, message: "Unexpected negated condition." }); |
| } |
| } |
| }; |
| } |
| }; |