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- 'use strict';
- const {isParenthesized, getParenthesizedText} = require('./utils/parentheses.js');
- const isSameReference = require('./utils/is-same-reference.js');
- const shouldAddParenthesesToLogicalExpressionChild = require('./utils/should-add-parentheses-to-logical-expression-child.js');
- const needsSemicolon = require('./utils/needs-semicolon.js');
- const MESSAGE_ID_ERROR = 'prefer-logical-operator-over-ternary/error';
- const MESSAGE_ID_SUGGESTION = 'prefer-logical-operator-over-ternary/suggestion';
- const messages = {
- [MESSAGE_ID_ERROR]: 'Prefer using a logical operator over a ternary.',
- [MESSAGE_ID_SUGGESTION]: 'Switch to `{{operator}}` operator.',
- };
- function isSameNode(left, right, sourceCode) {
- if (isSameReference(left, right)) {
- return true;
- }
- if (left.type !== right.type) {
- return false;
- }
- switch (left.type) {
- case 'AwaitExpression': {
- return isSameNode(left.argument, right.argument, sourceCode);
- }
- case 'LogicalExpression': {
- return (
- left.operator === right.operator
- && isSameNode(left.left, right.left, sourceCode)
- && isSameNode(left.right, right.right, sourceCode)
- );
- }
- case 'UnaryExpression': {
- return (
- left.operator === right.operator
- && left.prefix === right.prefix
- && isSameNode(left.argument, right.argument, sourceCode)
- );
- }
- case 'UpdateExpression': {
- return false;
- }
- // No default
- }
- return sourceCode.getText(left) === sourceCode.getText(right);
- }
- function fix({
- fixer,
- sourceCode,
- conditionalExpression,
- left,
- right,
- operator,
- }) {
- let text = [left, right].map((node, index) => {
- const isNodeParenthesized = isParenthesized(node, sourceCode);
- let text = isNodeParenthesized ? getParenthesizedText(node, sourceCode) : sourceCode.getText(node);
- if (
- !isNodeParenthesized
- && shouldAddParenthesesToLogicalExpressionChild(node, {operator, property: index === 0 ? 'left' : 'right'})
- ) {
- text = `(${text})`;
- }
- return text;
- }).join(` ${operator} `);
- // According to https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Operator_Precedence#table
- // There should be no cases need add parentheses when switching ternary to logical expression
- // ASI
- if (needsSemicolon(sourceCode.getTokenBefore(conditionalExpression), sourceCode, text)) {
- text = `;${text}`;
- }
- return fixer.replaceText(conditionalExpression, text);
- }
- function getProblem({
- sourceCode,
- conditionalExpression,
- left,
- right,
- }) {
- return {
- node: conditionalExpression,
- messageId: MESSAGE_ID_ERROR,
- suggest: ['??', '||'].map(operator => ({
- messageId: MESSAGE_ID_SUGGESTION,
- data: {operator},
- fix: fixer => fix({
- fixer,
- sourceCode,
- conditionalExpression,
- left,
- right,
- operator,
- }),
- })),
- };
- }
- /** @param {import('eslint').Rule.RuleContext} context */
- const create = context => {
- const sourceCode = context.getSourceCode();
- return {
- ConditionalExpression(conditionalExpression) {
- const {test, consequent, alternate} = conditionalExpression;
- // `foo ? foo : bar`
- if (isSameNode(test, consequent, sourceCode)) {
- return getProblem({
- sourceCode,
- conditionalExpression,
- left: test,
- right: alternate,
- });
- }
- // `!bar ? foo : bar`
- if (
- test.type === 'UnaryExpression'
- && test.operator === '!'
- && test.prefix
- && isSameNode(test.argument, alternate, sourceCode)
- ) {
- return getProblem({
- sourceCode,
- conditionalExpression,
- left: test.argument,
- right: consequent,
- });
- }
- },
- };
- };
- /** @type {import('eslint').Rule.RuleModule} */
- module.exports = {
- create,
- meta: {
- type: 'suggestion',
- docs: {
- description: 'Prefer using a logical operator over a ternary.',
- },
- hasSuggestions: true,
- messages,
- },
- };
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