brace-style.js

/**
 * @fileoverview Rule to flag block statements that do not use the one true brace style
 * @author Ian Christian Myers
 * @deprecated in ESLint v8.53.0
 */

"use strict";

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

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

/** @type {import('../types').Rule.RuleModule} */
module.exports = {
	meta: {
		deprecated: {
			message: "Formatting rules are being moved out of ESLint core.",
			url: "https://eslint.org/blog/2023/10/deprecating-formatting-rules/",
			deprecatedSince: "8.53.0",
			availableUntil: "11.0.0",
			replacedBy: [
				{
					message:
						"ESLint Stylistic now maintains deprecated stylistic core rules.",
					url: "https://eslint.style/guide/migration",
					plugin: {
						name: "@stylistic/eslint-plugin",
						url: "https://eslint.style",
					},
					rule: {
						name: "brace-style",
						url: "https://eslint.style/rules/brace-style",
					},
				},
			],
		},
		type: "layout",

		docs: {
			description: "Enforce consistent brace style for blocks",
			recommended: false,
			url: "https://eslint.org/docs/latest/rules/brace-style",
		},

		schema: [
			{
				enum: ["1tbs", "stroustrup", "allman"],
			},
			{
				type: "object",
				properties: {
					allowSingleLine: {
						type: "boolean",
						default: false,
					},
				},
				additionalProperties: false,
			},
		],

		fixable: "whitespace",

		messages: {
			nextLineOpen:
				"Opening curly brace does not appear on the same line as controlling statement.",
			sameLineOpen:
				"Opening curly brace appears on the same line as controlling statement.",
			blockSameLine:
				"Statement inside of curly braces should be on next line.",
			nextLineClose:
				"Closing curly brace does not appear on the same line as the subsequent block.",
			singleLineClose:
				"Closing curly brace should be on the same line as opening curly brace or on the line after the previous block.",
			sameLineClose:
				"Closing curly brace appears on the same line as the subsequent block.",
		},
	},

	create(context) {
		const style = context.options[0] || "1tbs",
			params = context.options[1] || {},
			sourceCode = context.sourceCode;

		//--------------------------------------------------------------------------
		// Helpers
		//--------------------------------------------------------------------------

		/**
		 * Fixes a place where a newline unexpectedly appears
		 * @param {Token} firstToken The token before the unexpected newline
		 * @param {Token} secondToken The token after the unexpected newline
		 * @returns {Function} A fixer function to remove the newlines between the tokens
		 */
		function removeNewlineBetween(firstToken, secondToken) {
			const textRange = [firstToken.range[1], secondToken.range[0]];
			const textBetween = sourceCode.text.slice(
				textRange[0],
				textRange[1],
			);

			// Don't do a fix if there is a comment between the tokens
			if (textBetween.trim()) {
				return null;
			}
			return fixer => fixer.replaceTextRange(textRange, " ");
		}

		/**
		 * Validates a pair of curly brackets based on the user's config
		 * @param {Token} openingCurly The opening curly bracket
		 * @param {Token} closingCurly The closing curly bracket
		 * @returns {void}
		 */
		function validateCurlyPair(openingCurly, closingCurly) {
			const tokenBeforeOpeningCurly =
				sourceCode.getTokenBefore(openingCurly);
			const tokenAfterOpeningCurly =
				sourceCode.getTokenAfter(openingCurly);
			const tokenBeforeClosingCurly =
				sourceCode.getTokenBefore(closingCurly);
			const singleLineException =
				params.allowSingleLine &&
				astUtils.isTokenOnSameLine(openingCurly, closingCurly);

			if (
				style !== "allman" &&
				!astUtils.isTokenOnSameLine(
					tokenBeforeOpeningCurly,
					openingCurly,
				)
			) {
				context.report({
					node: openingCurly,
					messageId: "nextLineOpen",
					fix: removeNewlineBetween(
						tokenBeforeOpeningCurly,
						openingCurly,
					),
				});
			}

			if (
				style === "allman" &&
				astUtils.isTokenOnSameLine(
					tokenBeforeOpeningCurly,
					openingCurly,
				) &&
				!singleLineException
			) {
				context.report({
					node: openingCurly,
					messageId: "sameLineOpen",
					fix: fixer => fixer.insertTextBefore(openingCurly, "\n"),
				});
			}

			if (
				astUtils.isTokenOnSameLine(
					openingCurly,
					tokenAfterOpeningCurly,
				) &&
				tokenAfterOpeningCurly !== closingCurly &&
				!singleLineException
			) {
				context.report({
					node: openingCurly,
					messageId: "blockSameLine",
					fix: fixer => fixer.insertTextAfter(openingCurly, "\n"),
				});
			}

			if (
				tokenBeforeClosingCurly !== openingCurly &&
				!singleLineException &&
				astUtils.isTokenOnSameLine(
					tokenBeforeClosingCurly,
					closingCurly,
				)
			) {
				context.report({
					node: closingCurly,
					messageId: "singleLineClose",
					fix: fixer => fixer.insertTextBefore(closingCurly, "\n"),
				});
			}
		}

		/**
		 * Validates the location of a token that appears before a keyword (e.g. a newline before `else`)
		 * @param {Token} curlyToken The closing curly token. This is assumed to precede a keyword token (such as `else` or `finally`).
		 * @returns {void}
		 */
		function validateCurlyBeforeKeyword(curlyToken) {
			const keywordToken = sourceCode.getTokenAfter(curlyToken);

			if (
				style === "1tbs" &&
				!astUtils.isTokenOnSameLine(curlyToken, keywordToken)
			) {
				context.report({
					node: curlyToken,
					messageId: "nextLineClose",
					fix: removeNewlineBetween(curlyToken, keywordToken),
				});
			}

			if (
				style !== "1tbs" &&
				astUtils.isTokenOnSameLine(curlyToken, keywordToken)
			) {
				context.report({
					node: curlyToken,
					messageId: "sameLineClose",
					fix: fixer => fixer.insertTextAfter(curlyToken, "\n"),
				});
			}
		}

		//--------------------------------------------------------------------------
		// Public API
		//--------------------------------------------------------------------------

		return {
			BlockStatement(node) {
				if (!astUtils.STATEMENT_LIST_PARENTS.has(node.parent.type)) {
					validateCurlyPair(
						sourceCode.getFirstToken(node),
						sourceCode.getLastToken(node),
					);
				}
			},
			StaticBlock(node) {
				validateCurlyPair(
					sourceCode.getFirstToken(node, { skip: 1 }), // skip the `static` token
					sourceCode.getLastToken(node),
				);
			},
			ClassBody(node) {
				validateCurlyPair(
					sourceCode.getFirstToken(node),
					sourceCode.getLastToken(node),
				);
			},
			SwitchStatement(node) {
				const closingCurly = sourceCode.getLastToken(node);
				const openingCurly = sourceCode.getTokenBefore(
					node.cases.length ? node.cases[0] : closingCurly,
				);

				validateCurlyPair(openingCurly, closingCurly);
			},
			IfStatement(node) {
				if (
					node.consequent.type === "BlockStatement" &&
					node.alternate
				) {
					// Handle the keyword after the `if` block (before `else`)
					validateCurlyBeforeKeyword(
						sourceCode.getLastToken(node.consequent),
					);
				}
			},
			TryStatement(node) {
				// Handle the keyword after the `try` block (before `catch` or `finally`)
				validateCurlyBeforeKeyword(sourceCode.getLastToken(node.block));

				if (node.handler && node.finalizer) {
					// Handle the keyword after the `catch` block (before `finally`)
					validateCurlyBeforeKeyword(
						sourceCode.getLastToken(node.handler.body),
					);
				}
			},
		};
	},
};