max-classes-per-file.js

/**
 * @fileoverview Enforce a maximum number of classes per file
 * @author James Garbutt <https://github.com/43081j>
 */
"use strict";

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


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

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

        docs: {
            description: "enforce a maximum number of classes per file",
            recommended: false,
            url: "https://eslint.org/docs/rules/max-classes-per-file"
        },

        schema: [
            {
                oneOf: [
                    {
                        type: "integer",
                        minimum: 1
                    },
                    {
                        type: "object",
                        properties: {
                            ignoreExpressions: {
                                type: "boolean"
                            },
                            max: {
                                type: "integer",
                                minimum: 1
                            }
                        },
                        additionalProperties: false
                    }
                ]
            }
        ],

        messages: {
            maximumExceeded: "File has too many classes ({{ classCount }}). Maximum allowed is {{ max }}."
        }
    },
    create(context) {
        const [option = {}] = context.options;
        const [ignoreExpressions, max] = typeof option === "number"
            ? [false, option || 1]
            : [option.ignoreExpressions, option.max || 1];

        let classCount = 0;

        return {
            Program() {
                classCount = 0;
            },
            "Program:exit"(node) {
                if (classCount > max) {
                    context.report({
                        node,
                        messageId: "maximumExceeded",
                        data: {
                            classCount,
                            max
                        }
                    });
                }
            },
            "ClassDeclaration"() {
                classCount++;
            },
            "ClassExpression"() {
                if (!ignoreExpressions) {
                    classCount++;
                }
            }
        };
    }
};