node_modules/eslint/lib/rules/dot-notation.js

/**
 * @fileoverview Rule to warn about using dot notation instead of square bracket notation when possible.
 * @author Josh Perez
 */
"use strict";

//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------

const astUtils = require("./utils/ast-utils");
const keywords = require("./utils/keywords");

//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

const validIdentifier = /^[a-zA-Z_$][\w$]*$/u;

// `null` literal must be handled separately.
const literalTypesToCheck = new Set(["string", "boolean"]);

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

		defaultOptions: [
			{
				allowKeywords: true,
				allowPattern: "",
			},
		],

		docs: {
			description: "Enforce dot notation whenever possible",
			recommended: false,
			frozen: true,
			url: "https://eslint.org/docs/latest/rules/dot-notation",
		},

		schema: [
			{
				type: "object",
				properties: {
					allowKeywords: {
						type: "boolean",
					},
					allowPattern: {
						type: "string",
					},
				},
				additionalProperties: false,
			},
		],

		fixable: "code",

		messages: {
			useDot: "[{{key}}] is better written in dot notation.",
			useBrackets: ".{{key}} is a syntax error.",
		},
	},

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

		let allowPattern;

		if (options.allowPattern) {
			allowPattern = new RegExp(options.allowPattern, "u");
		}

		/**
		 * Check if the property is valid dot notation
		 * @param {ASTNode} node The dot notation node
		 * @param {string} value Value which is to be checked
		 * @returns {void}
		 */
		function checkComputedProperty(node, value) {
			if (
				validIdentifier.test(value) &&
				(allowKeywords || !keywords.includes(String(value))) &&
				!(allowPattern && allowPattern.test(value))
			) {
				const formattedValue =
					node.property.type === "Literal"
						? JSON.stringify(value)
						: `\`${value}\``;

				context.report({
					node: node.property,
					messageId: "useDot",
					data: {
						key: formattedValue,
					},
					*fix(fixer) {
						const leftBracket = sourceCode.getTokenAfter(
							node.object,
							astUtils.isOpeningBracketToken,
						);
						const rightBracket = sourceCode.getLastToken(node);
						const nextToken = sourceCode.getTokenAfter(node);

						// Don't perform any fixes if there are comments inside the brackets.
						if (
							sourceCode.commentsExistBetween(
								leftBracket,
								rightBracket,
							)
						) {
							return;
						}

						// Replace the brackets by an identifier.
						if (!node.optional) {
							yield fixer.insertTextBefore(
								leftBracket,
								astUtils.isDecimalInteger(node.object)
									? " ."
									: ".",
							);
						}
						yield fixer.replaceTextRange(
							[leftBracket.range[0], rightBracket.range[1]],
							value,
						);

						// Insert a space after the property if it will be connected to the next token.
						if (
							nextToken &&
							rightBracket.range[1] === nextToken.range[0] &&
							!astUtils.canTokensBeAdjacent(
								String(value),
								nextToken,
							)
						) {
							yield fixer.insertTextAfter(node, " ");
						}
					},
				});
			}
		}

		return {
			MemberExpression(node) {
				if (
					node.computed &&
					node.property.type === "Literal" &&
					(literalTypesToCheck.has(typeof node.property.value) ||
						astUtils.isNullLiteral(node.property))
				) {
					checkComputedProperty(node, node.property.value);
				}
				if (
					node.computed &&
					astUtils.isStaticTemplateLiteral(node.property)
				) {
					checkComputedProperty(
						node,
						node.property.quasis[0].value.cooked,
					);
				}
				if (
					!allowKeywords &&
					!node.computed &&
					node.property.type === "Identifier" &&
					keywords.includes(String(node.property.name))
				) {
					context.report({
						node: node.property,
						messageId: "useBrackets",
						data: {
							key: node.property.name,
						},
						*fix(fixer) {
							const dotToken = sourceCode.getTokenBefore(
								node.property,
							);

							// A statement that starts with `let[` is parsed as a destructuring variable declaration, not a MemberExpression.
							if (
								node.object.type === "Identifier" &&
								node.object.name === "let" &&
								!node.optional
							) {
								return;
							}

							// Don't perform any fixes if there are comments between the dot and the property name.
							if (
								sourceCode.commentsExistBetween(
									dotToken,
									node.property,
								)
							) {
								return;
							}

							// Replace the identifier to brackets.
							if (!node.optional) {
								yield fixer.remove(dotToken);
							}
							yield fixer.replaceText(
								node.property,
								`["${node.property.name}"]`,
							);
						},
					});
				}
			},
		};
	},
};