eslint-plugin-lodash/lib/rules/prefer-constant.js

Lodash specific linting rules for ESLint

/**
 * @fileoverview Rule to check if the expression could be better expressed as a _.constant
 */
'use strict';

/**
 * @fileoverview Rule to check if the expression could be better expressed as a _.constant
 */
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------

module.exports = {
    meta: {
        schema: [{
            type: 'boolean'
        }, {
            type: 'boolean'
        }]
    },

    create: function create(context) {
        var _require = require('../util/astUtil');

        var getValueReturnedInFirstStatement = _require.getValueReturnedInFirstStatement;

        var shouldCheckArrowFunctions = context.options[0] !== undefined ? context.options[0] : true;
        var shouldCheckFunctionDeclarations = context.options[1] !== undefined ? context.options[1] : false;

        function isCompletelyLiteral(node) {
            switch (node.type) {
                case 'Literal':
                    return true;
                case 'BinaryExpression':
                    return isCompletelyLiteral(node.left) && isCompletelyLiteral(node.right);
                case 'UnaryExpression':
                    return isCompletelyLiteral(node.argument);
                case 'ConditionalExpression':
                    return isCompletelyLiteral(node.test) && isCompletelyLiteral(node.consequent) && isCompletelyLiteral(node.alternate);
                default:
                    return false;
            }
        }

        function reportIfLikeConstant(func, node) {
            var valueReturnedInFirstLine = func(node);
            if (valueReturnedInFirstLine && isCompletelyLiteral(valueReturnedInFirstLine)) {
                context.report(node, 'Prefer _.constant over a function returning a literal');
            }
        }

        function handleFunctionDefinition(node) {
            reportIfLikeConstant(getValueReturnedInFirstStatement, node);
        }

        return {
            FunctionExpression: handleFunctionDefinition,
            FunctionDeclaration: function FunctionDeclaration(node) {
                if (shouldCheckFunctionDeclarations) {
                    handleFunctionDefinition(node);
                }
            },
            ArrowFunctionExpression: function ArrowFunctionExpression(node) {
                if (shouldCheckArrowFunctions) {
                    handleFunctionDefinition(node);
                }
            }
        };
    }
};