oikos/web/node_modules/eslint/lib/rules/no-dupe-class-members.js

/**
 * @fileoverview A rule to disallow duplicate name in class members.
 * @author Toru Nagashima
 */

"use strict";

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

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

/** @type {import('../types').Rule.RuleModule} */
module.exports = {
	meta: {
		type: "problem",
		dialects: ["javascript", "typescript"],
		language: "javascript",

		docs: {
			description: "Disallow duplicate class members",
			recommended: true,
			url: "https://eslint.org/docs/latest/rules/no-dupe-class-members",
		},

		schema: [],

		messages: {
			unexpected: "Duplicate name '{{name}}'.",
		},
	},

	create(context) {
		let stack = [];

		/**
		 * Gets state of a given member name.
		 * @param {string} name A name of a member.
		 * @param {boolean} isStatic A flag which specifies that is a static member.
		 * @returns {Object} A state of a given member name.
		 *   - retv.init {boolean} A flag which shows the name is declared as normal member.
		 *   - retv.get {boolean} A flag which shows the name is declared as getter.
		 *   - retv.set {boolean} A flag which shows the name is declared as setter.
		 */
		function getState(name, isStatic) {
			const stateMap = stack.at(-1);
			const key = `$${name}`; // to avoid "__proto__".

			if (!stateMap[key]) {
				stateMap[key] = {
					nonStatic: { init: false, get: false, set: false },
					static: { init: false, get: false, set: false },
				};
			}

			return stateMap[key][isStatic ? "static" : "nonStatic"];
		}

		return {
			// Initializes the stack of state of member declarations.
			Program() {
				stack = [];
			},

			// Initializes state of member declarations for the class.
			ClassBody() {
				stack.push(Object.create(null));
			},

			// Disposes the state for the class.
			"ClassBody:exit"() {
				stack.pop();
			},

			// Reports the node if its name has been declared already.
			"MethodDefinition, PropertyDefinition"(node) {
				if (
					node.value &&
					node.value.type === "TSEmptyBodyFunctionExpression"
				) {
					return;
				}

				const name = astUtils.getStaticPropertyName(node);
				const kind =
					node.type === "MethodDefinition" ? node.kind : "field";

				if (name === null || kind === "constructor") {
					return;
				}

				const state = getState(name, node.static);
				let isDuplicate;

				if (kind === "get") {
					isDuplicate = state.init || state.get;
					state.get = true;
				} else if (kind === "set") {
					isDuplicate = state.init || state.set;
					state.set = true;
				} else {
					isDuplicate = state.init || state.get || state.set;
					state.init = true;
				}

				if (isDuplicate) {
					context.report({
						loc: node.key.loc,
						messageId: "unexpected",
						data: { name },
					});
				}
			},
		};
	},
};