codtracker-js/node_modules/eslint/lib/rules/no-useless-constructor.js

/**
 * @fileoverview Rule to flag the use of redundant constructors in classes.
 * @author Alberto Rodríguez
 */
'use strict';

const astUtils = require('./utils/ast-utils');

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

/**
 * Checks whether any of a method's parameters have a decorator or are a parameter property.
 * @param {ASTNode} node A method definition node.
 * @returns {boolean} `true` if any parameter had a decorator or is a parameter property.
 */
function hasDecoratorsOrParameterProperty(node) {
  return node.value.params.some(
    (param) => param.decorators?.length || param.type === 'TSParameterProperty'
  );
}

/**
 * Checks whether a node's accessibility makes it not useless.
 * @param {ASTNode} node A method definition node.
 * @returns {boolean} `true` if the node has a useful accessibility.
 */
function hasUsefulAccessibility(node) {
  switch (node.accessibility) {
    case 'protected':
    case 'private':
      return true;
    case 'public':
      return !!node.parent.parent.superClass;
    default:
      return false;
  }
}

/**
 * Checks whether a given array of statements is a single call of `super`.
 * @param {ASTNode[]} body An array of statements to check.
 * @returns {boolean} `true` if the body is a single call of `super`.
 */
function isSingleSuperCall(body) {
  return (
    body.length === 1 &&
    body[0].type === 'ExpressionStatement' &&
    body[0].expression.type === 'CallExpression' &&
    body[0].expression.callee.type === 'Super'
  );
}

/**
 * Checks whether a given node is a pattern which doesn't have any side effects.
 * Default parameters and Destructuring parameters can have side effects.
 * @param {ASTNode} node A pattern node.
 * @returns {boolean} `true` if the node doesn't have any side effects.
 */
function isSimple(node) {
  return node.type === 'Identifier' || node.type === 'RestElement';
}

/**
 * Checks whether a given array of expressions is `...arguments` or not.
 * `super(...arguments)` passes all arguments through.
 * @param {ASTNode[]} superArgs An array of expressions to check.
 * @returns {boolean} `true` if the superArgs is `...arguments`.
 */
function isSpreadArguments(superArgs) {
  return (
    superArgs.length === 1 &&
    superArgs[0].type === 'SpreadElement' &&
    superArgs[0].argument.type === 'Identifier' &&
    superArgs[0].argument.name === 'arguments'
  );
}

/**
 * Checks whether given 2 nodes are identifiers which have the same name or not.
 * @param {ASTNode} ctorParam A node to check.
 * @param {ASTNode} superArg A node to check.
 * @returns {boolean} `true` if the nodes are identifiers which have the same
 *      name.
 */
function isValidIdentifierPair(ctorParam, superArg) {
  return (
    ctorParam.type === 'Identifier' &&
    superArg.type === 'Identifier' &&
    ctorParam.name === superArg.name
  );
}

/**
 * Checks whether given 2 nodes are a rest/spread pair which has the same values.
 * @param {ASTNode} ctorParam A node to check.
 * @param {ASTNode} superArg A node to check.
 * @returns {boolean} `true` if the nodes are a rest/spread pair which has the
 *      same values.
 */
function isValidRestSpreadPair(ctorParam, superArg) {
  return (
    ctorParam.type === 'RestElement' &&
    superArg.type === 'SpreadElement' &&
    isValidIdentifierPair(ctorParam.argument, superArg.argument)
  );
}

/**
 * Checks whether given 2 nodes have the same value or not.
 * @param {ASTNode} ctorParam A node to check.
 * @param {ASTNode} superArg A node to check.
 * @returns {boolean} `true` if the nodes have the same value or not.
 */
function isValidPair(ctorParam, superArg) {
  return (
    isValidIdentifierPair(ctorParam, superArg) ||
    isValidRestSpreadPair(ctorParam, superArg)
  );
}

/**
 * Checks whether the parameters of a constructor and the arguments of `super()`
 * have the same values or not.
 * @param {ASTNode} ctorParams The parameters of a constructor to check.
 * @param {ASTNode} superArgs The arguments of `super()` to check.
 * @returns {boolean} `true` if those have the same values.
 */
function isPassingThrough(ctorParams, superArgs) {
  if (ctorParams.length !== superArgs.length) {
    return false;
  }

  for (let i = 0; i < ctorParams.length; ++i) {
    if (!isValidPair(ctorParams[i], superArgs[i])) {
      return false;
    }
  }

  return true;
}

/**
 * Checks whether the constructor body is a redundant super call.
 * @param {Array} body constructor body content.
 * @param {Array} ctorParams The params to check against super call.
 * @returns {boolean} true if the constructor body is redundant
 */
function isRedundantSuperCall(body, ctorParams) {
  return (
    isSingleSuperCall(body) &&
    ctorParams.every(isSimple) &&
    (isSpreadArguments(body[0].expression.arguments) ||
      isPassingThrough(ctorParams, body[0].expression.arguments))
  );
}

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

/** @type {import('../types').Rule.RuleModule} */
module.exports = {
  meta: {
    dialects: ['javascript', 'typescript'],
    language: 'javascript',
    type: 'suggestion',

    docs: {
      description: 'Disallow unnecessary constructors',
      recommended: false,
      url: 'https://eslint.org/docs/latest/rules/no-useless-constructor',
    },

    hasSuggestions: true,

    schema: [],

    messages: {
      noUselessConstructor: 'Useless constructor.',
      removeConstructor: 'Remove the constructor.',
    },
  },

  create(context) {
    /**
     * Checks whether a node is a redundant constructor
     * @param {ASTNode} node node to check
     * @returns {void}
     */
    function checkForConstructor(node) {
      if (
        node.kind !== 'constructor' ||
        node.value.type !== 'FunctionExpression' ||
        hasDecoratorsOrParameterProperty(node) ||
        hasUsefulAccessibility(node)
      ) {
        return;
      }

      /*
       * Prevent crashing on parsers which do not require class constructor
       * to have a body, e.g. typescript and flow
       */
      if (!node.value.body) {
        return;
      }

      const body = node.value.body.body;
      const ctorParams = node.value.params;
      const superClass = node.parent.parent.superClass;

      if (
        superClass ? isRedundantSuperCall(body, ctorParams) : body.length === 0
      ) {
        context.report({
          node,
          messageId: 'noUselessConstructor',
          suggest: [
            {
              messageId: 'removeConstructor',
              *fix(fixer) {
                const nextToken = context.sourceCode.getTokenAfter(node);
                const addSemiColon =
                  nextToken.type === 'Punctuator' &&
                  nextToken.value === '[' &&
                  astUtils.needsPrecedingSemicolon(context.sourceCode, node);

                yield fixer.replaceText(node, addSemiColon ? ';' : '');
              },
            },
          ],
        });
      }
    }

    return {
      MethodDefinition: checkForConstructor,
    };
  },
};