eslint-plugin-san/lib/rules/no-unused-vars.js

Official ESLint plugin for San

/**
 * @fileoverview disallow unused variable definitions of s-for directives or scope attributes.
 * @author 薛定谔的猫<hh_2013@foxmail.com>
 */
'use strict';

/* eslint-disable */

const utils = require('../utils');

/**
 * @typedef {VVariable['kind']} VariableKind
 */

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

/**
 * Groups variables by directive kind.
 * @param {VElement} node The element node
 * @returns { { [kind in VariableKind]?: VVariable[] } } The variables of grouped by directive kind.
 */
function groupingVariables(node) {
    /** @type { { [kind in VariableKind]?: VVariable[] } } */
    const result = {};
    for (const variable of node.variables) {
        const vars = result[variable.kind] || (result[variable.kind] = []);
        vars.push(variable);
    }
    return result;
}

/**
 * Checks if the given variable was defined by destructuring.
 * @param {VVariable} variable the given variable to check
 * @returns {boolean} `true` if the given variable was defined by destructuring.
 */
function isDestructuringVar(variable) {
    const node = variable.id;
    /** @type {ASTNode | null} */
    let parent = node.parent;
    while (parent) {
        if (parent.type === 'VForExpression' || parent.type === 'VSlotScopeExpression') {
            return false;
        }
        if (parent.type === 'Property' || parent.type === 'ArrayPattern') {
            return true;
        }
        parent = parent.parent;
    }
    return false;
}

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

module.exports = {
    meta: {
        type: 'suggestion',
        docs: {
            description: 'disallow unused variable definitions of s-for directives or scope attributes',
            categories: ['essential'],
            url: 'https://ecomfe.github.io/eslint-plugin-san/rules/no-unused-vars.html'
        },
        fixable: null,
        schema: [
            {
                type: 'object',
                properties: {
                    ignorePattern: {
                        type: 'string'
                    }
                },
                additionalProperties: false
            }
        ]
    },
    /** @param {RuleContext} context */
    create(context) {
        const option = context.options[0] || {};
        const ignorePattern = option.ignorePattern;
        /** @type {RegExp | null} */
        let ignoreRegEx = null;
        if (ignorePattern) {
            ignoreRegEx = new RegExp(ignorePattern, 'u');
        }
        return utils.defineTemplateBodyVisitor(context, {
            /**
             * @param {VElement} node
             */
            VElement(node) {
                const vars = groupingVariables(node);
                for (const variables of Object.values(vars)) {
                    if (!variables) {
                        continue;
                    }
                    
                    let hasAfterUsed = false;
                    for (let i = variables.length - 1; i >= 0; i--) {
                        const variable = variables[i];

                        if (variable.references.length) {
                            hasAfterUsed = true;
                            continue;
                        }

                        if (ignoreRegEx != null && ignoreRegEx.test(variable.id.name)) {
                            continue;
                        }

                        if (hasAfterUsed && !isDestructuringVar(variable)) {
                            // If a variable after the variable is used, it will be skipped.
                            continue;
                        }

                        context.report({
                            node: variable.id,
                            loc: variable.id.loc,
                            message: `'{{name}}' is defined but never used.`,
                            data: {
                                name: variable.id.name
                            },
                            suggest:
                                ignorePattern === '^_'
                                    ? [
                                          {
                                              desc: `Replace the ${variable.id.name} with _${variable.id.name}`,
                                              fix(fixer) {
                                                  return fixer.replaceText(variable.id, `_${variable.id.name}`);
                                              }
                                          }
                                      ]
                                    : []
                        });
                    }
                }
            }
        });
    }
};