safe-string-coercion.js — react Source File

Source Code

/**
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 *
 * @emails react-core
 */

'use strict';

function isEmptyLiteral(node) {
  return (
    node.type === 'Literal' &&
    typeof node.value === 'string' &&
    node.value === ''
  );
}

function isStringLiteral(node) {
  return (
    // TaggedTemplateExpressions can return non-strings
    (node.type === 'TemplateLiteral' &&
      node.parent.type !== 'TaggedTemplateExpression') ||
    (node.type === 'Literal' && typeof node.value === 'string')
  );
}

// Symbols and Temporal.* objects will throw when using `'' + value`, but that
// pattern can be faster than `String(value)` because JS engines can optimize
// `+` better in some cases. Therefore, in perf-sensitive production codepaths
// we require using `'' + value` for string coercion. The only exception is prod
// error handling code, because it's bad to crash while assembling an error
// message or call stack! Also, error-handling code isn't usually perf-critical.
//
// Non-production codepaths (tests, devtools extension, build tools, etc.)
// should use `String(value)` because it will never crash and the (small) perf
// difference doesn't matter enough for non-prod use cases.
//
// This rule assists enforcing these guidelines:
// * `'' + value` is flagged with a message to remind developers to add a DEV
//   check from shared/CheckStringCoercion.js to make sure that the user gets a
//   clear error message in DEV is the coercion will throw. These checks are not
//   needed if throwing is not possible, e.g. if the value is already known to
//   be a string or number.
// * `String(value)` is flagged only if the `isProductionUserAppCode` option
//   is set. Set this option for prod code files, and don't set it for non-prod
//   files.

const ignoreKeys = [
  'range',
  'raw',
  'parent',
  'loc',
  'start',
  'end',
  '_babelType',
  'leadingComments',
  'trailingComments',
];
// ... (315 more lines)