eslint/lib/rules/object-curly-newline.js

/**
 * @fileoverview Rule to require or disallow line breaks inside braces.
 * @author Toru Nagashima
 */

"use strict";

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

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

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

// Schema objects.
const OPTION_VALUE = {
    oneOf: [
        {
            enum: ["always", "never"]
        },
        {
            type: "object",
            properties: {
                multiline: {
                    type: "boolean"
                },
                minProperties: {
                    type: "integer",
                    minimum: 0
                },
                consistent: {
                    type: "boolean"
                }
            },
            additionalProperties: false,
            minProperties: 1
        }
    ]
};

/**
 * Normalizes a given option value.
 *
 * @param {string|Object|undefined} value - An option value to parse.
 * @returns {{multiline: boolean, minProperties: number, consistent: boolean}} Normalized option object.
 */
function normalizeOptionValue(value) {
    let multiline = false;
    let minProperties = Number.POSITIVE_INFINITY;
    let consistent = false;

    if (value) {
        if (value === "always") {
            minProperties = 0;
        } else if (value === "never") {
            minProperties = Number.POSITIVE_INFINITY;
        } else {
            multiline = Boolean(value.multiline);
            minProperties = value.minProperties || Number.POSITIVE_INFINITY;
            consistent = Boolean(value.consistent);
        }
    } else {
        consistent = true;
    }

    return { multiline, minProperties, consistent };
}

/**
 * Normalizes a given option value.
 *
 * @param {string|Object|undefined} options - An option value to parse.
 * @returns {{
 *   ObjectExpression: {multiline: boolean, minProperties: number, consistent: boolean},
 *   ObjectPattern: {multiline: boolean, minProperties: number, consistent: boolean},
 *   ImportDeclaration: {multiline: boolean, minProperties: number, consistent: boolean},
 *   ExportNamedDeclaration : {multiline: boolean, minProperties: number, consistent: boolean}
 * }} Normalized option object.
 */
function normalizeOptions(options) {
    const isNodeSpecificOption = lodash.overSome([lodash.isPlainObject, lodash.isString]);

    if (lodash.isPlainObject(options) && lodash.some(options, isNodeSpecificOption)) {
        return {
            ObjectExpression: normalizeOptionValue(options.ObjectExpression),
            ObjectPattern: normalizeOptionValue(options.ObjectPattern),
            ImportDeclaration: normalizeOptionValue(options.ImportDeclaration),
            ExportNamedDeclaration: normalizeOptionValue(options.ExportDeclaration)
        };
    }

    const value = normalizeOptionValue(options);

    return { ObjectExpression: value, ObjectPattern: value, ImportDeclaration: value, ExportNamedDeclaration: value };
}

/**
 * Determines if ObjectExpression, ObjectPattern, ImportDeclaration or ExportNamedDeclaration
 * node needs to be checked for missing line breaks
 *
 * @param {ASTNode} node - Node under inspection
 * @param {Object} options - option specific to node type
 * @param {Token} first - First object property
 * @param {Token} last - Last object property
 * @returns {boolean} `true` if node needs to be checked for missing line breaks
 */
function areLineBreaksRequired(node, options, first, last) {
    let objectProperties;

    if (node.type === "ObjectExpression" || node.type === "ObjectPattern") {
        objectProperties = node.properties;
    } else {

        // is ImportDeclaration or ExportNamedDeclaration
        objectProperties = node.specifiers
            .filter(s => s.type === "ImportSpecifier" || s.type === "ExportSpecifier");
    }

    return objectProperties.length >= options.minProperties ||
        (
            options.multiline &&
            objectProperties.length > 0 &&
            first.loc.start.line !== last.loc.end.line
        );
}

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

module.exports = {
    meta: {
        type: "layout",

        docs: {
            description: "enforce consistent line breaks inside braces",
            category: "Stylistic Issues",
            recommended: false,
            url: "https://eslint.org/docs/rules/object-curly-newline"
        },

        fixable: "whitespace",

        schema: [
            {
                oneOf: [
                    OPTION_VALUE,
                    {
                        type: "object",
                        properties: {
                            ObjectExpression: OPTION_VALUE,
                            ObjectPattern: OPTION_VALUE,
                            ImportDeclaration: OPTION_VALUE,
                            ExportDeclaration: OPTION_VALUE
                        },
                        additionalProperties: false,
                        minProperties: 1
                    }
                ]
            }
        ]
    },

    create(context) {
        const sourceCode = context.getSourceCode();
        const normalizedOptions = normalizeOptions(context.options[0]);

        /**
         * Reports a given node if it violated this rule.
         * @param {ASTNode} node - A node to check. This is an ObjectExpression, ObjectPattern, ImportDeclaration or ExportNamedDeclaration node.
         * @returns {void}
         */
        function check(node) {
            const options = normalizedOptions[node.type];

            if (
                (node.type === "ImportDeclaration" &&
                    !node.specifiers.some(specifier => specifier.type === "ImportSpecifier")) ||
                (node.type === "ExportNamedDeclaration" &&
                    !node.specifiers.some(specifier => specifier.type === "ExportSpecifier"))
            ) {
                return;
            }

            const openBrace = sourceCode.getFirstToken(node, token => token.value === "{");

            let closeBrace;

            if (node.typeAnnotation) {
                closeBrace = sourceCode.getTokenBefore(node.typeAnnotation);
            } else {
                closeBrace = sourceCode.getLastToken(node, token => token.value === "}");
            }

            let first = sourceCode.getTokenAfter(openBrace, { includeComments: true });
            let last = sourceCode.getTokenBefore(closeBrace, { includeComments: true });

            const needsLineBreaks = areLineBreaksRequired(node, options, first, last);

            const hasCommentsFirstToken = astUtils.isCommentToken(first);
            const hasCommentsLastToken = astUtils.isCommentToken(last);

            /*
             * Use tokens or comments to check multiline or not.
             * But use only tokens to check whether line breaks are needed.
             * This allows:
             *     var obj = { // eslint-disable-line foo
             *         a: 1
             *     }
             */
            first = sourceCode.getTokenAfter(openBrace);
            last = sourceCode.getTokenBefore(closeBrace);

            if (needsLineBreaks) {
                if (astUtils.isTokenOnSameLine(openBrace, first)) {
                    context.report({
                        message: "Expected a line break after this opening brace.",
                        node,
                        loc: openBrace.loc.start,
                        fix(fixer) {
                            if (hasCommentsFirstToken) {
                                return null;
                            }

                            return fixer.insertTextAfter(openBrace, "\n");
                        }
                    });
                }
                if (astUtils.isTokenOnSameLine(last, closeBrace)) {
                    context.report({
                        message: "Expected a line break before this closing brace.",
                        node,
                        loc: closeBrace.loc.start,
                        fix(fixer) {
                            if (hasCommentsLastToken) {
                                return null;
                            }

                            return fixer.insertTextBefore(closeBrace, "\n");
                        }
                    });
                }
            } else {
                const consistent = options.consistent;
                const hasLineBreakBetweenOpenBraceAndFirst = !astUtils.isTokenOnSameLine(openBrace, first);
                const hasLineBreakBetweenCloseBraceAndLast = !astUtils.isTokenOnSameLine(last, closeBrace);

                if (
                    (!consistent && hasLineBreakBetweenOpenBraceAndFirst) ||
                    (consistent && hasLineBreakBetweenOpenBraceAndFirst && !hasLineBreakBetweenCloseBraceAndLast)
                ) {
                    context.report({
                        message: "Unexpected line break after this opening brace.",
                        node,
                        loc: openBrace.loc.start,
                        fix(fixer) {
                            if (hasCommentsFirstToken) {
                                return null;
                            }

                            return fixer.removeRange([
                                openBrace.range[1],
                                first.range[0]
                            ]);
                        }
                    });
                }
                if (
                    (!consistent && hasLineBreakBetweenCloseBraceAndLast) ||
                    (consistent && !hasLineBreakBetweenOpenBraceAndFirst && hasLineBreakBetweenCloseBraceAndLast)
                ) {
                    context.report({
                        message: "Unexpected line break before this closing brace.",
                        node,
                        loc: closeBrace.loc.start,
                        fix(fixer) {
                            if (hasCommentsLastToken) {
                                return null;
                            }

                            return fixer.removeRange([
                                last.range[1],
                                closeBrace.range[0]
                            ]);
                        }
                    });
                }
            }
        }

        return {
            ObjectExpression: check,
            ObjectPattern: check,
            ImportDeclaration: check,
            ExportNamedDeclaration: check
        };
    }
};