react-native-macos/Libraries/Renderer/src/renderers/shared/stack/reconciler/traverseStackChildren.js

A framework for building native macOS apps using React

/**
 * Copyright 2013-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree. An additional grant
 * of patent rights can be found in the PATENTS file in the same directory.
 *
 * @providesModule traverseStackChildren
 */

'use strict';

var REACT_ELEMENT_TYPE = require('ReactElementSymbol');

var getIteratorFn = require('getIteratorFn');
var invariant = require('fbjs/lib/invariant');
var KeyEscapeUtils = require('KeyEscapeUtils');
var warning = require('fbjs/lib/warning');

if (__DEV__) {
  var {
    getCurrentStackAddendum,
  } = require('ReactGlobalSharedState').ReactComponentTreeHook;
}

var SEPARATOR = '.';
var SUBSEPARATOR = ':';

/**
 * This is inlined from ReactElement since this file is shared between
 * isomorphic and renderers. We could extract this to a
 *
 */

/**
 * TODO: Test that a single child and an array with one item have the same key
 * pattern.
 */

var didWarnAboutMaps = false;

/**
 * Generate a key string that identifies a component within a set.
 *
 * @param {*} component A component that could contain a manual key.
 * @param {number} index Index that is used if a manual key is not provided.
 * @return {string}
 */
function getComponentKey(component, index) {
  // Do some typechecking here since we call this blindly. We want to ensure
  // that we don't block potential future ES APIs.
  if (component && typeof component === 'object' && component.key != null) {
    // Explicit key
    return KeyEscapeUtils.escape(component.key);
  }
  // Implicit key determined by the index in the set
  return index.toString(36);
}

/**
 * @param {?*} children Children tree container.
 * @param {!string} nameSoFar Name of the key path so far.
 * @param {!function} callback Callback to invoke with each child found.
 * @param {?*} traverseContext Used to pass information throughout the traversal
 * process.
 * @return {!number} The number of children in this subtree.
 */
function traverseStackChildrenImpl(
  children,
  nameSoFar,
  callback,
  traverseContext,
) {
  var type = typeof children;

  if (type === 'undefined' || type === 'boolean') {
    // All of the above are perceived as null.
    children = null;
  }

  if (
    children === null ||
    type === 'string' ||
    type === 'number' ||
    // The following is inlined from ReactElement. This means we can optimize
    // some checks. React Fiber also inlines this logic for similar purposes.
    (type === 'object' && children.$$typeof === REACT_ELEMENT_TYPE)
  ) {
    callback(
      traverseContext,
      children,
      // If it's the only child, treat the name as if it was wrapped in an array
      // so that it's consistent if the number of children grows.
      nameSoFar === '' ? SEPARATOR + getComponentKey(children, 0) : nameSoFar,
    );
    return 1;
  }

  var child;
  var nextName;
  var subtreeCount = 0; // Count of children found in the current subtree.
  var nextNamePrefix = nameSoFar === '' ? SEPARATOR : nameSoFar + SUBSEPARATOR;

  if (Array.isArray(children)) {
    for (var i = 0; i < children.length; i++) {
      child = children[i];
      nextName = nextNamePrefix + getComponentKey(child, i);
      subtreeCount += traverseStackChildrenImpl(
        child,
        nextName,
        callback,
        traverseContext,
      );
    }
  } else {
    var iteratorFn = getIteratorFn(children);
    if (iteratorFn) {
      if (__DEV__) {
        // Warn about using Maps as children
        if (iteratorFn === children.entries) {
          warning(
            didWarnAboutMaps,
            'Using Maps as children is unsupported and will likely yield ' +
              'unexpected results. Convert it to a sequence/iterable of keyed ' +
              'ReactElements instead.%s',
            getCurrentStackAddendum(),
          );
          didWarnAboutMaps = true;
        }
      }

      var iterator = iteratorFn.call(children);
      var step;
      var ii = 0;
      while (!(step = iterator.next()).done) {
        child = step.value;
        nextName = nextNamePrefix + getComponentKey(child, ii++);
        subtreeCount += traverseStackChildrenImpl(
          child,
          nextName,
          callback,
          traverseContext,
        );
      }
    } else if (type === 'object') {
      var addendum = '';
      if (__DEV__) {
        addendum =
          ' If you meant to render a collection of children, use an array ' +
          'instead.' +
          getCurrentStackAddendum();
      }
      var childrenString = '' + children;
      invariant(
        false,
        'Objects are not valid as a React child (found: %s).%s',
        childrenString === '[object Object]'
          ? 'object with keys {' + Object.keys(children).join(', ') + '}'
          : childrenString,
        addendum,
      );
    }
  }

  return subtreeCount;
}

/**
 * Traverses children that are typically specified as `props.children`, but
 * might also be specified through attributes:
 *
 * - `traverseStackChildren(this.props.children, ...)`
 * - `traverseStackChildren(this.props.leftPanelChildren, ...)`
 *
 * The `traverseContext` is an optional argument that is passed through the
 * entire traversal. It can be used to store accumulations or anything else that
 * the callback might find relevant.
 *
 * @param {?*} children Children tree object.
 * @param {!function} callback To invoke upon traversing each child.
 * @param {?*} traverseContext Context for traversal.
 * @return {!number} The number of children in this subtree.
 */
function traverseStackChildren(children, callback, traverseContext) {
  if (children == null) {
    return 0;
  }

  return traverseStackChildrenImpl(children, '', callback, traverseContext);
}

module.exports = traverseStackChildren;