camelcase.js

/**
 * @fileoverview Rule to flag non-camelcased identifiers
 * @author Nicholas C. Zakas
 */

"use strict";

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

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

        docs: {
            description: "enforce camelcase naming convention",
            recommended: false,
            url: "https://eslint.org/docs/rules/camelcase"
        },

        schema: [
            {
                type: "object",
                properties: {
                    ignoreDestructuring: {
                        type: "boolean",
                        default: false
                    },
                    ignoreImports: {
                        type: "boolean",
                        default: false
                    },
                    ignoreGlobals: {
                        type: "boolean",
                        default: false
                    },
                    properties: {
                        enum: ["always", "never"]
                    },
                    allow: {
                        type: "array",
                        items: [
                            {
                                type: "string"
                            }
                        ],
                        minItems: 0,
                        uniqueItems: true
                    }
                },
                additionalProperties: false
            }
        ],

        messages: {
            notCamelCase: "Identifier '{{name}}' is not in camel case.",
            notCamelCasePrivate: "#{{name}} is not in camel case."
        }
    },

    create(context) {
        const options = context.options[0] || {};
        const properties = options.properties === "never" ? "never" : "always";
        const ignoreDestructuring = options.ignoreDestructuring;
        const ignoreImports = options.ignoreImports;
        const ignoreGlobals = options.ignoreGlobals;
        const allow = options.allow || [];

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

        // contains reported nodes to avoid reporting twice on destructuring with shorthand notation
        const reported = new Set();

        /**
         * Checks if a string contains an underscore and isn't all upper-case
         * @param {string} name The string to check.
         * @returns {boolean} if the string is underscored
         * @private
         */
        function isUnderscored(name) {
            const nameBody = name.replace(/^_+|_+$/gu, "");

            // if there's an underscore, it might be A_CONSTANT, which is okay
            return nameBody.includes("_") && nameBody !== nameBody.toUpperCase();
        }

        /**
         * Checks if a string match the ignore list
         * @param {string} name The string to check.
         * @returns {boolean} if the string is ignored
         * @private
         */
        function isAllowed(name) {
            return allow.some(
                entry => name === entry || name.match(new RegExp(entry, "u"))
            );
        }

        /**
         * Checks if a given name is good or not.
         * @param {string} name The name to check.
         * @returns {boolean} `true` if the name is good.
         * @private
         */
        function isGoodName(name) {
            return !isUnderscored(name) || isAllowed(name);
        }

        /**
         * Checks if a given identifier reference or member expression is an assignment
         * target.
         * @param {ASTNode} node The node to check.
         * @returns {boolean} `true` if the node is an assignment target.
         */
        function isAssignmentTarget(node) {
            const parent = node.parent;

            switch (parent.type) {
                case "AssignmentExpression":
                case "AssignmentPattern":
                    return parent.left === node;

                case "Property":
                    return (
                        parent.parent.type === "ObjectPattern" &&
                        parent.value === node
                    );
                case "ArrayPattern":
                case "RestElement":
                    return true;

                default:
                    return false;
            }
        }

        /**
         * Checks if a given binding identifier uses the original name as-is.
         * - If it's in object destructuring, the original name is its property name.
         * - If it's in import declaration, the original name is its exported name.
         * @param {ASTNode} node The `Identifier` node to check.
         * @returns {boolean} `true` if the identifier uses the original name as-is.
         */
        function equalsToOriginalName(node) {
            const localName = node.name;
            const valueNode = node.parent.type === "AssignmentPattern"
                ? node.parent
                : node;
            const parent = valueNode.parent;

            switch (parent.type) {
                case "Property":
                    return (
                        parent.parent.type === "ObjectPattern" &&
                        parent.value === valueNode &&
                        !parent.computed &&
                        parent.key.type === "Identifier" &&
                        parent.key.name === localName
                    );

                case "ImportSpecifier":
                    return (
                        parent.local === node &&
                        parent.imported.name === localName
                    );

                default:
                    return false;
            }
        }

        /**
         * Reports an AST node as a rule violation.
         * @param {ASTNode} node The node to report.
         * @returns {void}
         * @private
         */
        function report(node) {
            if (reported.has(node.range[0])) {
                return;
            }
            reported.add(node.range[0]);

            // Report it.
            context.report({
                node,
                messageId: node.type === "PrivateIdentifier"
                    ? "notCamelCasePrivate"
                    : "notCamelCase",
                data: { name: node.name }
            });
        }

        /**
         * Reports an identifier reference or a binding identifier.
         * @param {ASTNode} node The `Identifier` node to report.
         * @returns {void}
         */
        function reportReferenceId(node) {

            /*
             * For backward compatibility, if it's in callings then ignore it.
             * Not sure why it is.
             */
            if (
                node.parent.type === "CallExpression" ||
                node.parent.type === "NewExpression"
            ) {
                return;
            }

            /*
             * For backward compatibility, if it's a default value of
             * destructuring/parameters then ignore it.
             * Not sure why it is.
             */
            if (
                node.parent.type === "AssignmentPattern" &&
                node.parent.right === node
            ) {
                return;
            }

            /*
             * The `ignoreDestructuring` flag skips the identifiers that uses
             * the property name as-is.
             */
            if (ignoreDestructuring && equalsToOriginalName(node)) {
                return;
            }

            report(node);
        }

        return {

            // Report camelcase of global variable references ------------------
            Program() {
                const scope = context.getScope();

                if (!ignoreGlobals) {

                    // Defined globals in config files or directive comments.
                    for (const variable of scope.variables) {
                        if (
                            variable.identifiers.length > 0 ||
                            isGoodName(variable.name)
                        ) {
                            continue;
                        }
                        for (const reference of variable.references) {

                            /*
                             * For backward compatibility, this rule reports read-only
                             * references as well.
                             */
                            reportReferenceId(reference.identifier);
                        }
                    }
                }

                // Undefined globals.
                for (const reference of scope.through) {
                    const id = reference.identifier;

                    if (isGoodName(id.name)) {
                        continue;
                    }

                    /*
                     * For backward compatibility, this rule reports read-only
                     * references as well.
                     */
                    reportReferenceId(id);
                }
            },

            // Report camelcase of declared variables --------------------------
            [[
                "VariableDeclaration",
                "FunctionDeclaration",
                "FunctionExpression",
                "ArrowFunctionExpression",
                "ClassDeclaration",
                "ClassExpression",
                "CatchClause"
            ]](node) {
                for (const variable of context.getDeclaredVariables(node)) {
                    if (isGoodName(variable.name)) {
                        continue;
                    }
                    const id = variable.identifiers[0];

                    // Report declaration.
                    if (!(ignoreDestructuring && equalsToOriginalName(id))) {
                        report(id);
                    }

                    /*
                     * For backward compatibility, report references as well.
                     * It looks unnecessary because declarations are reported.
                     */
                    for (const reference of variable.references) {
                        if (reference.init) {
                            continue; // Skip the write references of initializers.
                        }
                        reportReferenceId(reference.identifier);
                    }
                }
            },

            // Report camelcase in properties ----------------------------------
            [[
                "ObjectExpression > Property[computed!=true] > Identifier.key",
                "MethodDefinition[computed!=true] > Identifier.key",
                "PropertyDefinition[computed!=true] > Identifier.key",
                "MethodDefinition > PrivateIdentifier.key",
                "PropertyDefinition > PrivateIdentifier.key"
            ]](node) {
                if (properties === "never" || isGoodName(node.name)) {
                    return;
                }
                report(node);
            },
            "MemberExpression[computed!=true] > Identifier.property"(node) {
                if (
                    properties === "never" ||
                    !isAssignmentTarget(node.parent) || // ← ignore read-only references.
                    isGoodName(node.name)
                ) {
                    return;
                }
                report(node);
            },

            // Report camelcase in import --------------------------------------
            ImportDeclaration(node) {
                for (const variable of context.getDeclaredVariables(node)) {
                    if (isGoodName(variable.name)) {
                        continue;
                    }
                    const id = variable.identifiers[0];

                    // Report declaration.
                    if (!(ignoreImports && equalsToOriginalName(id))) {
                        report(id);
                    }

                    /*
                     * For backward compatibility, report references as well.
                     * It looks unnecessary because declarations are reported.
                     */
                    for (const reference of variable.references) {
                        reportReferenceId(reference.identifier);
                    }
                }
            },

            // Report camelcase in re-export -----------------------------------
            [[
                "ExportAllDeclaration > Identifier.exported",
                "ExportSpecifier > Identifier.exported"
            ]](node) {
                if (isGoodName(node.name)) {
                    return;
                }
                report(node);
            },

            // Report camelcase in labels --------------------------------------
            [[
                "LabeledStatement > Identifier.label",

                /*
                 * For backward compatibility, report references as well.
                 * It looks unnecessary because declarations are reported.
                 */
                "BreakStatement > Identifier.label",
                "ContinueStatement > Identifier.label"
            ]](node) {
                if (isGoodName(node.name)) {
                    return;
                }
                report(node);
            }
        };
    }
};