@hapi/eslint-plugin/lib/rules/scope-start.js

ESLint plugin containing hapi style guide rules and config

'use strict';

const internals = {};


module.exports = {
    meta: {
        type: 'layout',
        docs: {
            description: 'enforce new line at the beginning of function scope',
            category: 'Stylistic Issues',
            recommended: true
        },
        schema: [{
            enum: ['allow-one-liners']
        }, {
            type: 'integer'
        }],
        messages: {
            missingBlank: 'Missing blank line at beginning of function.'
        }
    },
    create(context) {

        const sourceCode = context.sourceCode ?? context.getSourceCode();

        const maxInOneLiner = context.options[1] !== undefined ? context.options[1] : 1;

        const checkFunction = function (node) {

            const allowOneLiners = context.options[0] === 'allow-one-liners';
            check(node, allowOneLiners);
        };

        const checkArrow = function (node) {

            check(node, true);
        };

        const check = function (node, allowOneLiners) {

            const fnBody = node.body;

            // Arrow functions can return literals that span multiple lines

            if (fnBody.type === 'ObjectExpression' ||
                fnBody.type === 'ArrayExpression') {

                return;
            }

            const isBlockBody = fnBody.type === 'BlockStatement';
            const body = isBlockBody ? fnBody.body : [fnBody];

            // Allow empty function bodies to be of any size

            if (body.length === 0) {
                return;
            }

            const stmt = body[0];
            const bodyStartLine = stmt.loc.start.line;
            const openTokenLine = sourceCode.getTokenBefore(stmt).loc.start.line;
            const closeTokenLine = isBlockBody ? sourceCode.getTokenAfter(stmt).loc.start.line : sourceCode.getLastToken(stmt).loc.start.line;

            if (allowOneLiners === true &&
                body.length <= maxInOneLiner &&
                openTokenLine === closeTokenLine) {

                return;
            }

            if (bodyStartLine - openTokenLine < 2) {
                context.report({ node, messageId: 'missingBlank' });
            }
        };

        return {
            ArrowFunctionExpression: checkArrow,
            FunctionExpression: checkFunction,
            FunctionDeclaration: checkFunction
        };
    }
};