+++ /dev/null
-/**
- * @fileoverview Rule to flag no-unneeded-ternary
- * @author Gyandeep Singh
- */
-
-"use strict";
-
-const astUtils = require("./utils/ast-utils");
-
-// Operators that always result in a boolean value
-const BOOLEAN_OPERATORS = new Set(["==", "===", "!=", "!==", ">", ">=", "<", "<=", "in", "instanceof"]);
-const OPERATOR_INVERSES = {
- "==": "!=",
- "!=": "==",
- "===": "!==",
- "!==": "==="
-
- // Operators like < and >= are not true inverses, since both will return false with NaN.
-};
-const OR_PRECEDENCE = astUtils.getPrecedence({ type: "LogicalExpression", operator: "||" });
-
-//------------------------------------------------------------------------------
-// Rule Definition
-//------------------------------------------------------------------------------
-
-module.exports = {
- meta: {
- type: "suggestion",
-
- docs: {
- description: "disallow ternary operators when simpler alternatives exist",
- category: "Stylistic Issues",
- recommended: false,
- url: "https://eslint.org/docs/rules/no-unneeded-ternary"
- },
-
- schema: [
- {
- type: "object",
- properties: {
- defaultAssignment: {
- type: "boolean",
- default: true
- }
- },
- additionalProperties: false
- }
- ],
-
- fixable: "code"
- },
-
- create(context) {
- const options = context.options[0] || {};
- const defaultAssignment = options.defaultAssignment !== false;
- const sourceCode = context.getSourceCode();
-
- /**
- * Test if the node is a boolean literal
- * @param {ASTNode} node The node to report.
- * @returns {boolean} True if the its a boolean literal
- * @private
- */
- function isBooleanLiteral(node) {
- return node.type === "Literal" && typeof node.value === "boolean";
- }
-
- /**
- * Creates an expression that represents the boolean inverse of the expression represented by the original node
- * @param {ASTNode} node A node representing an expression
- * @returns {string} A string representing an inverted expression
- */
- function invertExpression(node) {
- if (node.type === "BinaryExpression" && Object.prototype.hasOwnProperty.call(OPERATOR_INVERSES, node.operator)) {
- const operatorToken = sourceCode.getFirstTokenBetween(
- node.left,
- node.right,
- token => token.value === node.operator
- );
- const text = sourceCode.getText();
-
- return text.slice(node.range[0],
- operatorToken.range[0]) + OPERATOR_INVERSES[node.operator] + text.slice(operatorToken.range[1], node.range[1]);
- }
-
- if (astUtils.getPrecedence(node) < astUtils.getPrecedence({ type: "UnaryExpression" })) {
- return `!(${astUtils.getParenthesisedText(sourceCode, node)})`;
- }
- return `!${astUtils.getParenthesisedText(sourceCode, node)}`;
- }
-
- /**
- * Tests if a given node always evaluates to a boolean value
- * @param {ASTNode} node An expression node
- * @returns {boolean} True if it is determined that the node will always evaluate to a boolean value
- */
- function isBooleanExpression(node) {
- return node.type === "BinaryExpression" && BOOLEAN_OPERATORS.has(node.operator) ||
- node.type === "UnaryExpression" && node.operator === "!";
- }
-
- /**
- * Test if the node matches the pattern id ? id : expression
- * @param {ASTNode} node The ConditionalExpression to check.
- * @returns {boolean} True if the pattern is matched, and false otherwise
- * @private
- */
- function matchesDefaultAssignment(node) {
- return node.test.type === "Identifier" &&
- node.consequent.type === "Identifier" &&
- node.test.name === node.consequent.name;
- }
-
- return {
-
- ConditionalExpression(node) {
- if (isBooleanLiteral(node.alternate) && isBooleanLiteral(node.consequent)) {
- context.report({
- node,
- loc: node.consequent.loc.start,
- message: "Unnecessary use of boolean literals in conditional expression.",
- fix(fixer) {
- if (node.consequent.value === node.alternate.value) {
-
- // Replace `foo ? true : true` with just `true`, but don't replace `foo() ? true : true`
- return node.test.type === "Identifier" ? fixer.replaceText(node, node.consequent.value.toString()) : null;
- }
- if (node.alternate.value) {
-
- // Replace `foo() ? false : true` with `!(foo())`
- return fixer.replaceText(node, invertExpression(node.test));
- }
-
- // Replace `foo ? true : false` with `foo` if `foo` is guaranteed to be a boolean, or `!!foo` otherwise.
-
- return fixer.replaceText(node, isBooleanExpression(node.test) ? astUtils.getParenthesisedText(sourceCode, node.test) : `!${invertExpression(node.test)}`);
- }
- });
- } else if (!defaultAssignment && matchesDefaultAssignment(node)) {
- context.report({
- node,
- loc: node.consequent.loc.start,
- message: "Unnecessary use of conditional expression for default assignment.",
- fix: fixer => {
- const shouldParenthesizeAlternate = (
- astUtils.getPrecedence(node.alternate) < OR_PRECEDENCE &&
- !astUtils.isParenthesised(sourceCode, node.alternate)
- );
- const alternateText = shouldParenthesizeAlternate
- ? `(${sourceCode.getText(node.alternate)})`
- : astUtils.getParenthesisedText(sourceCode, node.alternate);
- const testText = astUtils.getParenthesisedText(sourceCode, node.test);
-
- return fixer.replaceText(node, `${testText} || ${alternateText}`);
- }
- });
- }
- }
- };
- }
-};
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