codtracker-js/node_modules/eslint/lib/rules/no-unneeded-ternary.js

/**
 * @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
//------------------------------------------------------------------------------

/** @type {import('../types').Rule.RuleModule} */
module.exports = {
	meta: {
		type: "suggestion",

		defaultOptions: [{ defaultAssignment: true }],

		docs: {
			description:
				"Disallow ternary operators when simpler alternatives exist",
			recommended: false,
			frozen: true,
			url: "https://eslint.org/docs/latest/rules/no-unneeded-ternary",
		},

		schema: [
			{
				type: "object",
				properties: {
					defaultAssignment: {
						type: "boolean",
					},
				},
				additionalProperties: false,
			},
		],

		fixable: "code",

		messages: {
			unnecessaryConditionalExpression:
				"Unnecessary use of boolean literals in conditional expression.",
			unnecessaryConditionalAssignment:
				"Unnecessary use of conditional expression for default assignment.",
		},
	},

	create(context) {
		const [{ defaultAssignment }] = context.options;
		const sourceCode = context.sourceCode;

		/**
		 * 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.hasOwn(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,
						messageId: "unnecessaryConditionalExpression",
						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,
										)
									: `!${invertExpression(node.test)}`,
							);
						},
					});
				} else if (
					!defaultAssignment &&
					matchesDefaultAssignment(node)
				) {
					context.report({
						node,
						messageId: "unnecessaryConditionalAssignment",
						fix(fixer) {
							const shouldParenthesizeAlternate =
								(astUtils.getPrecedence(node.alternate) <
									OR_PRECEDENCE ||
									astUtils.isCoalesceExpression(
										node.alternate,
									)) &&
								!astUtils.isParenthesised(
									sourceCode,
									node.alternate,
								);
							const alternateText = shouldParenthesizeAlternate
								? `(${sourceCode.getText(node.alternate)})`
								: astUtils.getParenthesisedText(
										sourceCode,
										node.alternate,
									);
							const testText = astUtils.getParenthesisedText(
								sourceCode,
								node.test,
							);

							return fixer.replaceText(
								node,
								`${testText} || ${alternateText}`,
							);
						},
					});
				}
			},
		};
	},
};