frontend/node_modules/eslint/lib/rules/curly.js

/**
 * @fileoverview Rule to flag statements without curly braces
 * @author Nicholas C. Zakas
 */
"use strict";

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

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

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

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

		docs: {
			description:
				"Enforce consistent brace style for all control statements",
			recommended: false,
			frozen: true,
			url: "https://eslint.org/docs/latest/rules/curly",
		},

		schema: {
			anyOf: [
				{
					type: "array",
					items: [
						{
							enum: ["all"],
						},
					],
					minItems: 0,
					maxItems: 1,
				},
				{
					type: "array",
					items: [
						{
							enum: ["multi", "multi-line", "multi-or-nest"],
						},
						{
							enum: ["consistent"],
						},
					],
					minItems: 0,
					maxItems: 2,
				},
			],
		},

		defaultOptions: ["all"],

		fixable: "code",

		messages: {
			missingCurlyAfter: "Expected { after '{{name}}'.",
			missingCurlyAfterCondition:
				"Expected { after '{{name}}' condition.",
			unexpectedCurlyAfter: "Unnecessary { after '{{name}}'.",
			unexpectedCurlyAfterCondition:
				"Unnecessary { after '{{name}}' condition.",
		},
	},

	create(context) {
		const multiOnly = context.options[0] === "multi";
		const multiLine = context.options[0] === "multi-line";
		const multiOrNest = context.options[0] === "multi-or-nest";
		const consistent = context.options[1] === "consistent";

		const sourceCode = context.sourceCode;

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

		/**
		 * Determines if a given node is a one-liner that's on the same line as it's preceding code.
		 * @param {ASTNode} node The node to check.
		 * @returns {boolean} True if the node is a one-liner that's on the same line as it's preceding code.
		 * @private
		 */
		function isCollapsedOneLiner(node) {
			const before = sourceCode.getTokenBefore(node);
			const last = sourceCode.getLastToken(node);
			const lastExcludingSemicolon = astUtils.isSemicolonToken(last)
				? sourceCode.getTokenBefore(last)
				: last;

			return (
				before.loc.start.line === lastExcludingSemicolon.loc.end.line
			);
		}

		/**
		 * Determines if a given node is a one-liner.
		 * @param {ASTNode} node The node to check.
		 * @returns {boolean} True if the node is a one-liner.
		 * @private
		 */
		function isOneLiner(node) {
			if (node.type === "EmptyStatement") {
				return true;
			}

			const first = sourceCode.getFirstToken(node);
			const last = sourceCode.getLastToken(node);
			const lastExcludingSemicolon = astUtils.isSemicolonToken(last)
				? sourceCode.getTokenBefore(last)
				: last;

			return first.loc.start.line === lastExcludingSemicolon.loc.end.line;
		}

		/**
		 * Determines if a semicolon needs to be inserted after removing a set of curly brackets, in order to avoid a SyntaxError.
		 * @param {Token} closingBracket The } token
		 * @returns {boolean} `true` if a semicolon needs to be inserted after the last statement in the block.
		 */
		function needsSemicolon(closingBracket) {
			const tokenBefore = sourceCode.getTokenBefore(closingBracket);
			const tokenAfter = sourceCode.getTokenAfter(closingBracket);
			const lastBlockNode = sourceCode.getNodeByRangeIndex(
				tokenBefore.range[0],
			);

			if (astUtils.isSemicolonToken(tokenBefore)) {
				// If the last statement already has a semicolon, don't add another one.
				return false;
			}

			if (!tokenAfter) {
				// If there are no statements after this block, there is no need to add a semicolon.
				return false;
			}

			if (
				lastBlockNode.type === "BlockStatement" &&
				lastBlockNode.parent.type !== "FunctionExpression" &&
				lastBlockNode.parent.type !== "ArrowFunctionExpression"
			) {
				/*
				 * If the last node surrounded by curly brackets is a BlockStatement (other than a FunctionExpression or an ArrowFunctionExpression),
				 * don't insert a semicolon. Otherwise, the semicolon would be parsed as a separate statement, which would cause
				 * a SyntaxError if it was followed by `else`.
				 */
				return false;
			}

			if (tokenBefore.loc.end.line === tokenAfter.loc.start.line) {
				// If the next token is on the same line, insert a semicolon.
				return true;
			}

			if (/^[([/`+-]/u.test(tokenAfter.value)) {
				// If the next token starts with a character that would disrupt ASI, insert a semicolon.
				return true;
			}

			if (
				tokenBefore.type === "Punctuator" &&
				(tokenBefore.value === "++" || tokenBefore.value === "--")
			) {
				// If the last token is ++ or --, insert a semicolon to avoid disrupting ASI.
				return true;
			}

			// Otherwise, do not insert a semicolon.
			return false;
		}

		/**
		 * Prepares to check the body of a node to see if it's a block statement.
		 * @param {ASTNode} node The node to report if there's a problem.
		 * @param {ASTNode} body The body node to check for blocks.
		 * @param {string} name The name to report if there's a problem.
		 * @param {{ condition: boolean }} opts Options to pass to the report functions
		 * @returns {Object} a prepared check object, with "actual", "expected", "check" properties.
		 *   "actual" will be `true` or `false` whether the body is already a block statement.
		 *   "expected" will be `true` or `false` if the body should be a block statement or not, or
		 *   `null` if it doesn't matter, depending on the rule options. It can be modified to change
		 *   the final behavior of "check".
		 *   "check" will be a function reporting appropriate problems depending on the other
		 *   properties.
		 */
		function prepareCheck(node, body, name, opts) {
			const hasBlock = body.type === "BlockStatement";
			let expected = null;

			if (
				hasBlock &&
				(body.body.length !== 1 ||
					astUtils.areBracesNecessary(body, sourceCode))
			) {
				expected = true;
			} else if (multiOnly) {
				expected = false;
			} else if (multiLine) {
				if (!isCollapsedOneLiner(body)) {
					expected = true;
				}

				// otherwise, the body is allowed to have braces or not to have braces
			} else if (multiOrNest) {
				if (hasBlock) {
					const statement = body.body[0];
					const leadingCommentsInBlock =
						sourceCode.getCommentsBefore(statement);

					expected =
						!isOneLiner(statement) ||
						leadingCommentsInBlock.length > 0;
				} else {
					expected = !isOneLiner(body);
				}
			} else {
				// default "all"
				expected = true;
			}

			return {
				actual: hasBlock,
				expected,
				check() {
					if (
						this.expected !== null &&
						this.expected !== this.actual
					) {
						if (this.expected) {
							context.report({
								node,
								loc: body.loc,
								messageId:
									opts && opts.condition
										? "missingCurlyAfterCondition"
										: "missingCurlyAfter",
								data: {
									name,
								},
								fix: fixer =>
									fixer.replaceText(
										body,
										`{${sourceCode.getText(body)}}`,
									),
							});
						} else {
							context.report({
								node,
								loc: body.loc,
								messageId:
									opts && opts.condition
										? "unexpectedCurlyAfterCondition"
										: "unexpectedCurlyAfter",
								data: {
									name,
								},
								fix(fixer) {
									/*
									 * `do while` expressions sometimes need a space to be inserted after `do`.
									 * e.g. `do{foo()} while (bar)` should be corrected to `do foo() while (bar)`
									 */
									const needsPrecedingSpace =
										node.type === "DoWhileStatement" &&
										sourceCode.getTokenBefore(body)
											.range[1] === body.range[0] &&
										!astUtils.canTokensBeAdjacent(
											"do",
											sourceCode.getFirstToken(body, {
												skip: 1,
											}),
										);

									const openingBracket =
										sourceCode.getFirstToken(body);
									const closingBracket =
										sourceCode.getLastToken(body);
									const lastTokenInBlock =
										sourceCode.getTokenBefore(
											closingBracket,
										);

									if (needsSemicolon(closingBracket)) {
										/*
										 * If removing braces would cause a SyntaxError due to multiple statements on the same line (or
										 * change the semantics of the code due to ASI), don't perform a fix.
										 */
										return null;
									}

									const resultingBodyText =
										sourceCode
											.getText()
											.slice(
												openingBracket.range[1],
												lastTokenInBlock.range[0],
											) +
										sourceCode.getText(lastTokenInBlock) +
										sourceCode
											.getText()
											.slice(
												lastTokenInBlock.range[1],
												closingBracket.range[0],
											);

									return fixer.replaceText(
										body,
										(needsPrecedingSpace ? " " : "") +
											resultingBodyText,
									);
								},
							});
						}
					}
				},
			};
		}

		/**
		 * Prepares to check the bodies of a "if", "else if" and "else" chain.
		 * @param {ASTNode} node The first IfStatement node of the chain.
		 * @returns {Object[]} prepared checks for each body of the chain. See `prepareCheck` for more
		 *   information.
		 */
		function prepareIfChecks(node) {
			const preparedChecks = [];

			for (
				let currentNode = node;
				currentNode;
				currentNode = currentNode.alternate
			) {
				preparedChecks.push(
					prepareCheck(currentNode, currentNode.consequent, "if", {
						condition: true,
					}),
				);
				if (
					currentNode.alternate &&
					currentNode.alternate.type !== "IfStatement"
				) {
					preparedChecks.push(
						prepareCheck(
							currentNode,
							currentNode.alternate,
							"else",
						),
					);
					break;
				}
			}

			if (consistent) {
				/*
				 * If any node should have or already have braces, make sure they
				 * all have braces.
				 * If all nodes shouldn't have braces, make sure they don't.
				 */
				const expected = preparedChecks.some(preparedCheck => {
					if (preparedCheck.expected !== null) {
						return preparedCheck.expected;
					}
					return preparedCheck.actual;
				});

				preparedChecks.forEach(preparedCheck => {
					preparedCheck.expected = expected;
				});
			}

			return preparedChecks;
		}

		//--------------------------------------------------------------------------
		// Public
		//--------------------------------------------------------------------------

		return {
			IfStatement(node) {
				const parent = node.parent;
				const isElseIf =
					parent.type === "IfStatement" && parent.alternate === node;

				if (!isElseIf) {
					// This is a top `if`, check the whole `if-else-if` chain
					prepareIfChecks(node).forEach(preparedCheck => {
						preparedCheck.check();
					});
				}

				// Skip `else if`, it's already checked (when the top `if` was visited)
			},

			WhileStatement(node) {
				prepareCheck(node, node.body, "while", {
					condition: true,
				}).check();
			},

			DoWhileStatement(node) {
				prepareCheck(node, node.body, "do").check();
			},

			ForStatement(node) {
				prepareCheck(node, node.body, "for", {
					condition: true,
				}).check();
			},

			ForInStatement(node) {
				prepareCheck(node, node.body, "for-in").check();
			},

			ForOfStatement(node) {
				prepareCheck(node, node.body, "for-of").check();
			},
		};
	},
};