codtracker-js/node_modules/eslint/lib/rules/no-useless-computed-key.js

/**
 * @fileoverview Rule to disallow unnecessary computed property keys in object literals
 * @author Burak Yigit Kaya
 */
'use strict';

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

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

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

/**
 * Determines whether the computed key syntax is unnecessarily used for the given node.
 * In particular, it determines whether removing the square brackets and using the content between them
 * directly as the key (e.g. ['foo'] -> 'foo') would produce valid syntax and preserve the same behavior.
 * Valid non-computed keys are only: identifiers, number literals and string literals.
 * Only literals can preserve the same behavior, with a few exceptions for specific node types:
 * Property
 *   - { ["__proto__"]: foo } defines a property named "__proto__"
 *     { "__proto__": foo } defines object's prototype
 * PropertyDefinition
 *   - class C { ["constructor"]; } defines an instance field named "constructor"
 *     class C { "constructor"; } produces a parsing error
 *   - class C { static ["constructor"]; } defines a static field named "constructor"
 *     class C { static "constructor"; } produces a parsing error
 *   - class C { static ["prototype"]; } produces a runtime error (doesn't break the whole script)
 *     class C { static "prototype"; } produces a parsing error (breaks the whole script)
 * MethodDefinition
 *   - class C { ["constructor"]() {} } defines a prototype method named "constructor"
 *     class C { "constructor"() {} } defines the constructor
 *   - class C { static ["prototype"]() {} } produces a runtime error (doesn't break the whole script)
 *     class C { static "prototype"() {} } produces a parsing error (breaks the whole script)
 * @param {ASTNode} node The node to check. It can be `Property`, `PropertyDefinition` or `MethodDefinition`.
 * @throws {Error} (Unreachable.)
 * @returns {void} `true` if the node has useless computed key.
 */
function hasUselessComputedKey(node) {
  if (!node.computed) {
    return false;
  }

  const { key } = node;

  if (key.type !== 'Literal') {
    return false;
  }

  const { value } = key;

  if (typeof value !== 'number' && typeof value !== 'string') {
    return false;
  }

  switch (node.type) {
    case 'Property':
      if (node.parent.type === 'ObjectExpression') {
        return value !== '__proto__';
      }
      return true;

    case 'PropertyDefinition':
      if (node.static) {
        return value !== 'constructor' && value !== 'prototype';
      }

      return value !== 'constructor';

    case 'MethodDefinition':
      if (node.static) {
        return value !== 'prototype';
      }

      return value !== 'constructor';

    /* c8 ignore next */
    default:
      throw new Error(`Unexpected node type: ${node.type}`);
  }
}

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

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

    defaultOptions: [
      {
        enforceForClassMembers: true,
      },
    ],

    docs: {
      description:
        'Disallow unnecessary computed property keys in objects and classes',
      recommended: false,
      frozen: true,
      url: 'https://eslint.org/docs/latest/rules/no-useless-computed-key',
    },

    schema: [
      {
        type: 'object',
        properties: {
          enforceForClassMembers: {
            type: 'boolean',
          },
        },
        additionalProperties: false,
      },
    ],
    fixable: 'code',

    messages: {
      unnecessarilyComputedProperty:
        'Unnecessarily computed property [{{property}}] found.',
    },
  },
  create(context) {
    const sourceCode = context.sourceCode;
    const [{ enforceForClassMembers }] = context.options;

    /**
     * Reports a given node if it violated this rule.
     * @param {ASTNode} node The node to check.
     * @returns {void}
     */
    function check(node) {
      if (hasUselessComputedKey(node)) {
        const { key } = node;

        context.report({
          node,
          messageId: 'unnecessarilyComputedProperty',
          data: { property: sourceCode.getText(key) },
          fix(fixer) {
            const leftSquareBracket = sourceCode.getTokenBefore(
              key,
              astUtils.isOpeningBracketToken
            );
            const rightSquareBracket = sourceCode.getTokenAfter(
              key,
              astUtils.isClosingBracketToken
            );

            // If there are comments between the brackets and the property name, don't do a fix.
            if (
              sourceCode.commentsExistBetween(
                leftSquareBracket,
                rightSquareBracket
              )
            ) {
              return null;
            }

            const tokenBeforeLeftBracket =
              sourceCode.getTokenBefore(leftSquareBracket);

            // Insert a space before the key to avoid changing identifiers, e.g. ({ get[2]() {} }) to ({ get2() {} })
            const needsSpaceBeforeKey =
              tokenBeforeLeftBracket.range[1] === leftSquareBracket.range[0] &&
              !astUtils.canTokensBeAdjacent(
                tokenBeforeLeftBracket,
                sourceCode.getFirstToken(key)
              );

            const replacementKey = (needsSpaceBeforeKey ? ' ' : '') + key.raw;

            return fixer.replaceTextRange(
              [leftSquareBracket.range[0], rightSquareBracket.range[1]],
              replacementKey
            );
          },
        });
      }
    }

    /**
     * A no-op function to act as placeholder for checking a node when the `enforceForClassMembers` option is `false`.
     * @returns {void}
     * @private
     */
    function noop() {}

    return {
      Property: check,
      MethodDefinition: enforceForClassMembers ? check : noop,
      PropertyDefinition: enforceForClassMembers ? check : noop,
    };
  },
};