some progress

node_modules/mongoose/lib/helpers/populate/SkipPopulateValue.js

@@ -0,0 +1,10 @@
+'use strict';
+
+module.exports = function SkipPopulateValue(val) {
+  if (!(this instanceof SkipPopulateValue)) {
+    return new SkipPopulateValue(val);
+  }
+
+  this.val = val;
+  return this;
+};

node_modules/mongoose/lib/helpers/populate/assignRawDocsToIdStructure.js

@@ -0,0 +1,125 @@
+'use strict';
+
+const clone = require('../../helpers/clone');
+const leanPopulateMap = require('./leanPopulateMap');
+const modelSymbol = require('../symbols').modelSymbol;
+const utils = require('../../utils');
+
+module.exports = assignRawDocsToIdStructure;
+
+const kHasArray = Symbol('assignRawDocsToIdStructure.hasArray');
+
+/**
+ * Assign `vals` returned by mongo query to the `rawIds`
+ * structure returned from utils.getVals() honoring
+ * query sort order if specified by user.
+ *
+ * This can be optimized.
+ *
+ * Rules:
+ *
+ *   if the value of the path is not an array, use findOne rules, else find.
+ *   for findOne the results are assigned directly to doc path (including null results).
+ *   for find, if user specified sort order, results are assigned directly
+ *   else documents are put back in original order of array if found in results
+ *
+ * @param {Array} rawIds
+ * @param {Array} resultDocs
+ * @param {Array} resultOrder
+ * @param {Object} options
+ * @param {Boolean} recursed
+ * @api private
+ */
+
+function assignRawDocsToIdStructure(rawIds, resultDocs, resultOrder, options, recursed) {
+  // honor user specified sort order
+  const newOrder = [];
+  const sorting = options.sort && rawIds.length > 1;
+  const nullIfNotFound = options.$nullIfNotFound;
+  let doc;
+  let sid;
+  let id;
+
+  if (utils.isMongooseArray(rawIds)) {
+    rawIds = rawIds.__array;
+  }
+
+  let i = 0;
+  const len = rawIds.length;
+
+  if (sorting && recursed && options[kHasArray] === undefined) {
+    options[kHasArray] = false;
+    for (const key in resultOrder) {
+      if (Array.isArray(resultOrder[key])) {
+        options[kHasArray] = true;
+        break;
+      }
+    }
+  }
+
+  for (i = 0; i < len; ++i) {
+    id = rawIds[i];
+
+    if (Array.isArray(id)) {
+      // handle [ [id0, id2], [id3] ]
+      assignRawDocsToIdStructure(id, resultDocs, resultOrder, options, true);
+      newOrder.push(id);
+      continue;
+    }
+
+    if (id === null && sorting === false) {
+      // keep nulls for findOne unless sorting, which always
+      // removes them (backward compat)
+      newOrder.push(id);
+      continue;
+    }
+
+    sid = String(id);
+    doc = resultDocs[sid];
+    // If user wants separate copies of same doc, use this option
+    if (options.clone && doc != null) {
+      if (options.lean) {
+        const _model = leanPopulateMap.get(doc);
+        doc = clone(doc);
+        leanPopulateMap.set(doc, _model);
+      } else {
+        doc = doc.constructor.hydrate(doc._doc);
+      }
+    }
+
+    if (recursed) {
+      if (doc) {
+        if (sorting) {
+          const _resultOrder = resultOrder[sid];
+          if (options[kHasArray]) {
+            // If result arrays, rely on the MongoDB server response for ordering
+            newOrder.push(doc);
+          } else {
+            newOrder[_resultOrder] = doc;
+          }
+        } else {
+          newOrder.push(doc);
+        }
+      } else if (id != null && id[modelSymbol] != null) {
+        newOrder.push(id);
+      } else {
+        newOrder.push(options.retainNullValues || nullIfNotFound ? null : id);
+      }
+    } else {
+      // apply findOne behavior - if document in results, assign, else assign null
+      newOrder[i] = doc || null;
+    }
+  }
+
+  rawIds.length = 0;
+  if (newOrder.length) {
+    // reassign the documents based on corrected order
+
+    // forEach skips over sparse entries in arrays so we
+    // can safely use this to our advantage dealing with sorted
+    // result sets too.
+    newOrder.forEach(function(doc, i) {
+      rawIds[i] = doc;
+    });
+  }
+}

node_modules/mongoose/lib/helpers/populate/assignVals.js

@@ -0,0 +1,341 @@
+'use strict';
+
+const MongooseMap = require('../../types/map');
+const SkipPopulateValue = require('./SkipPopulateValue');
+const assignRawDocsToIdStructure = require('./assignRawDocsToIdStructure');
+const get = require('../get');
+const getVirtual = require('./getVirtual');
+const leanPopulateMap = require('./leanPopulateMap');
+const lookupLocalFields = require('./lookupLocalFields');
+const markArraySubdocsPopulated = require('./markArraySubdocsPopulated');
+const mpath = require('mpath');
+const sift = require('sift').default;
+const utils = require('../../utils');
+const { populateModelSymbol } = require('../symbols');
+
+module.exports = function assignVals(o) {
+  // Options that aren't explicitly listed in `populateOptions`
+  const userOptions = Object.assign({}, get(o, 'allOptions.options.options'), get(o, 'allOptions.options'));
+  // `o.options` contains options explicitly listed in `populateOptions`, like
+  // `match` and `limit`.
+  const populateOptions = Object.assign({}, o.options, userOptions, {
+    justOne: o.justOne
+  });
+  populateOptions.$nullIfNotFound = o.isVirtual;
+  const populatedModel = o.populatedModel;
+
+  const originalIds = [].concat(o.rawIds);
+
+  // replace the original ids in our intermediate _ids structure
+  // with the documents found by query
+  o.allIds = [].concat(o.allIds);
+  assignRawDocsToIdStructure(o.rawIds, o.rawDocs, o.rawOrder, populateOptions);
+
+  // now update the original documents being populated using the
+  // result structure that contains real documents.
+  const docs = o.docs;
+  const rawIds = o.rawIds;
+  const options = o.options;
+  const count = o.count && o.isVirtual;
+  let i;
+
+  function setValue(val) {
+    if (count) {
+      return val;
+    }
+    if (val instanceof SkipPopulateValue) {
+      return val.val;
+    }
+    if (val === void 0) {
+      return val;
+    }
+
+    const _allIds = o.allIds[i];
+
+    if (o.path.endsWith('.$*')) {
+      // Skip maps re: gh-12494
+      return valueFilter(val, options, populateOptions, _allIds);
+    }
+
+    if (o.justOne === true && Array.isArray(val)) {
+      // Might be an embedded discriminator (re: gh-9244) with multiple models, so make sure to pick the right
+      // model before assigning.
+      const ret = [];
+      for (const doc of val) {
+        const _docPopulatedModel = leanPopulateMap.get(doc);
+        if (_docPopulatedModel == null || _docPopulatedModel === populatedModel) {
+          ret.push(doc);
+        }
+      }
+      // Since we don't want to have to create a new mongoosearray, make sure to
+      // modify the array in place
+      while (val.length > ret.length) {
+        Array.prototype.pop.apply(val, []);
+      }
+      for (let i = 0; i < ret.length; ++i) {
+        val[i] = ret[i];
+      }
+
+      return valueFilter(val[0], options, populateOptions, _allIds);
+    } else if (o.justOne === false && !Array.isArray(val)) {
+      return valueFilter([val], options, populateOptions, _allIds);
+    }
+    return valueFilter(val, options, populateOptions, _allIds);
+  }
+
+  for (i = 0; i < docs.length; ++i) {
+    const _path = o.path.endsWith('.$*') ? o.path.slice(0, -3) : o.path;
+    const existingVal = mpath.get(_path, docs[i], lookupLocalFields);
+    if (existingVal == null && !getVirtual(o.originalModel.schema, _path)) {
+      continue;
+    }
+
+    let valueToSet;
+    if (count) {
+      valueToSet = numDocs(rawIds[i]);
+    } else if (Array.isArray(o.match)) {
+      valueToSet = Array.isArray(rawIds[i]) ?
+        rawIds[i].filter(sift(o.match[i])) :
+        [rawIds[i]].filter(sift(o.match[i]))[0];
+    } else {
+      valueToSet = rawIds[i];
+    }
+
+    // If we're populating a map, the existing value will be an object, so
+    // we need to transform again
+    const originalSchema = o.originalModel.schema;
+    const isDoc = get(docs[i], '$__', null) != null;
+    let isMap = isDoc ?
+      existingVal instanceof Map :
+      utils.isPOJO(existingVal);
+    // If we pass the first check, also make sure the local field's schematype
+    // is map (re: gh-6460)
+    isMap = isMap && get(originalSchema._getSchema(_path), '$isSchemaMap');
+    if (!o.isVirtual && isMap) {
+      const _keys = existingVal instanceof Map ?
+        Array.from(existingVal.keys()) :
+        Object.keys(existingVal);
+      valueToSet = valueToSet.reduce((cur, v, i) => {
+        cur.set(_keys[i], v);
+        return cur;
+      }, new Map());
+    }
+
+    if (isDoc && Array.isArray(valueToSet)) {
+      for (const val of valueToSet) {
+        if (val != null && val.$__ != null) {
+          val.$__.parent = docs[i];
+        }
+      }
+    } else if (isDoc && valueToSet != null && valueToSet.$__ != null) {
+      valueToSet.$__.parent = docs[i];
+    }
+
+    if (o.isVirtual && isDoc) {
+      docs[i].$populated(_path, o.justOne ? originalIds[0] : originalIds, o.allOptions);
+      // If virtual populate and doc is already init-ed, need to walk through
+      // the actual doc to set rather than setting `_doc` directly
+      if (Array.isArray(valueToSet)) {
+        valueToSet = valueToSet.map(v => v == null ? void 0 : v);
+      }
+      mpath.set(_path, valueToSet, docs[i], void 0, setValue, false);
+      continue;
+    }
+
+    const parts = _path.split('.');
+    let cur = docs[i];
+    const curPath = parts[0];
+    for (let j = 0; j < parts.length - 1; ++j) {
+      // If we get to an array with a dotted path, like `arr.foo`, don't set
+      // `foo` on the array.
+      if (Array.isArray(cur) && !utils.isArrayIndex(parts[j])) {
+        break;
+      }
+
+      if (parts[j] === '$*') {
+        break;
+      }
+
+      if (cur[parts[j]] == null) {
+        // If nothing to set, avoid creating an unnecessary array. Otherwise
+        // we'll end up with a single doc in the array with only defaults.
+        // See gh-8342, gh-8455
+        const schematype = originalSchema._getSchema(curPath);
+        if (valueToSet == null && schematype != null && schematype.$isMongooseArray) {
+          break;
+        }
+        cur[parts[j]] = {};
+      }
+      cur = cur[parts[j]];
+      // If the property in MongoDB is a primitive, we won't be able to populate
+      // the nested path, so skip it. See gh-7545
+      if (typeof cur !== 'object') {
+        break;
+      }
+    }
+    if (docs[i].$__) {
+      o.allOptions.options[populateModelSymbol] = o.allOptions.model;
+      docs[i].$populated(_path, o.unpopulatedValues[i], o.allOptions.options);
+
+      if (valueToSet != null && valueToSet.$__ != null) {
+        valueToSet.$__.wasPopulated = { value: o.unpopulatedValues[i] };
+      }
+
+      if (valueToSet instanceof Map && !valueToSet.$isMongooseMap) {
+        valueToSet = new MongooseMap(valueToSet, _path, docs[i], docs[i].schema.path(_path).$__schemaType);
+      }
+    }
+
+    // If lean, need to check that each individual virtual respects
+    // `justOne`, because you may have a populated virtual with `justOne`
+    // underneath an array. See gh-6867
+    mpath.set(_path, valueToSet, docs[i], lookupLocalFields, setValue, false);
+
+    if (docs[i].$__) {
+      markArraySubdocsPopulated(docs[i], [o.allOptions.options]);
+    }
+  }
+};
+
+function numDocs(v) {
+  if (Array.isArray(v)) {
+    // If setting underneath an array of populated subdocs, we may have an
+    // array of arrays. See gh-7573
+    if (v.some(el => Array.isArray(el) || el === null)) {
+      return v.map(el => {
+        if (el == null) {
+          return 0;
+        }
+        if (Array.isArray(el)) {
+          return el.filter(el => el != null).length;
+        }
+        return 1;
+      });
+    }
+    return v.filter(el => el != null).length;
+  }
+  return v == null ? 0 : 1;
+}
+
+/**
+ * 1) Apply backwards compatible find/findOne behavior to sub documents
+ *
+ *    find logic:
+ *      a) filter out non-documents
+ *      b) remove _id from sub docs when user specified
+ *
+ *    findOne
+ *      a) if no doc found, set to null
+ *      b) remove _id from sub docs when user specified
+ *
+ * 2) Remove _ids when specified by users query.
+ *
+ * background:
+ * _ids are left in the query even when user excludes them so
+ * that population mapping can occur.
+ * @param {Any} val
+ * @param {Object} assignmentOpts
+ * @param {Object} populateOptions
+ * @param {Function} [populateOptions.transform]
+ * @param {Boolean} allIds
+ * @api private
+ */
+
+function valueFilter(val, assignmentOpts, populateOptions, allIds) {
+  const userSpecifiedTransform = typeof populateOptions.transform === 'function';
+  const transform = userSpecifiedTransform ? populateOptions.transform : noop;
+  if (Array.isArray(val)) {
+    // find logic
+    const ret = [];
+    const numValues = val.length;
+    for (let i = 0; i < numValues; ++i) {
+      let subdoc = val[i];
+      const _allIds = Array.isArray(allIds) ? allIds[i] : allIds;
+      if (!isPopulatedObject(subdoc) && (!populateOptions.retainNullValues || subdoc != null) && !userSpecifiedTransform) {
+        continue;
+      } else if (!populateOptions.retainNullValues && subdoc == null) {
+        continue;
+      } else if (userSpecifiedTransform) {
+        subdoc = transform(isPopulatedObject(subdoc) ? subdoc : null, _allIds);
+      }
+      maybeRemoveId(subdoc, assignmentOpts);
+      ret.push(subdoc);
+      if (assignmentOpts.originalLimit &&
+          ret.length >= assignmentOpts.originalLimit) {
+        break;
+      }
+    }
+
+    const rLen = ret.length;
+    // Since we don't want to have to create a new mongoosearray, make sure to
+    // modify the array in place
+    while (val.length > rLen) {
+      Array.prototype.pop.apply(val, []);
+    }
+    let i = 0;
+    if (utils.isMongooseArray(val)) {
+      for (i = 0; i < rLen; ++i) {
+        val.set(i, ret[i], true);
+      }
+    } else {
+      for (i = 0; i < rLen; ++i) {
+        val[i] = ret[i];
+      }
+    }
+    return val;
+  }
+
+  // findOne
+  if (isPopulatedObject(val) || utils.isPOJO(val)) {
+    maybeRemoveId(val, assignmentOpts);
+    return transform(val, allIds);
+  }
+  if (val instanceof Map) {
+    return val;
+  }
+
+  if (populateOptions.justOne === false) {
+    return [];
+  }
+
+  return val == null ? transform(val, allIds) : transform(null, allIds);
+}
+
+/**
+ * Remove _id from `subdoc` if user specified "lean" query option
+ * @param {Document} subdoc
+ * @param {Object} assignmentOpts
+ * @api private
+ */
+
+function maybeRemoveId(subdoc, assignmentOpts) {
+  if (subdoc != null && assignmentOpts.excludeId) {
+    if (typeof subdoc.$__setValue === 'function') {
+      delete subdoc._doc._id;
+    } else {
+      delete subdoc._id;
+    }
+  }
+}
+
+/**
+ * Determine if `obj` is something we can set a populated path to. Can be a
+ * document, a lean document, or an array/map that contains docs.
+ * @param {Any} obj
+ * @api private
+ */
+
+function isPopulatedObject(obj) {
+  if (obj == null) {
+    return false;
+  }
+
+  return Array.isArray(obj) ||
+    obj.$isMongooseMap ||
+    obj.$__ != null ||
+    leanPopulateMap.has(obj);
+}
+
+function noop(v) {
+  return v;
+}

node_modules/mongoose/lib/helpers/populate/createPopulateQueryFilter.js

@@ -0,0 +1,97 @@
+'use strict';
+
+const SkipPopulateValue = require('./SkipPopulateValue');
+const parentPaths = require('../path/parentPaths');
+const { trusted } = require('../query/trusted');
+const hasDollarKeys = require('../query/hasDollarKeys');
+
+module.exports = function createPopulateQueryFilter(ids, _match, _foreignField, model, skipInvalidIds) {
+  const match = _formatMatch(_match);
+
+  if (_foreignField.size === 1) {
+    const foreignField = Array.from(_foreignField)[0];
+    const foreignSchemaType = model.schema.path(foreignField);
+    if (foreignField !== '_id' || !match['_id']) {
+      ids = _filterInvalidIds(ids, foreignSchemaType, skipInvalidIds);
+      match[foreignField] = trusted({ $in: ids });
+    } else if (foreignField === '_id' && match['_id']) {
+      const userSpecifiedMatch = hasDollarKeys(match[foreignField]) ?
+        match[foreignField] :
+        { $eq: match[foreignField] };
+      match[foreignField] = { ...trusted({ $in: ids }), ...userSpecifiedMatch };
+    }
+
+    const _parentPaths = parentPaths(foreignField);
+    for (let i = 0; i < _parentPaths.length - 1; ++i) {
+      const cur = _parentPaths[i];
+      if (match[cur] != null && match[cur].$elemMatch != null) {
+        match[cur].$elemMatch[foreignField.slice(cur.length + 1)] = trusted({ $in: ids });
+        delete match[foreignField];
+        break;
+      }
+    }
+  } else {
+    const $or = [];
+    if (Array.isArray(match.$or)) {
+      match.$and = [{ $or: match.$or }, { $or: $or }];
+      delete match.$or;
+    } else {
+      match.$or = $or;
+    }
+    for (const foreignField of _foreignField) {
+      if (foreignField !== '_id' || !match['_id']) {
+        const foreignSchemaType = model.schema.path(foreignField);
+        ids = _filterInvalidIds(ids, foreignSchemaType, skipInvalidIds);
+        $or.push({ [foreignField]: { $in: ids } });
+      } else if (foreignField === '_id' && match['_id']) {
+        const userSpecifiedMatch = hasDollarKeys(match[foreignField]) ?
+          match[foreignField] :
+          { $eq: match[foreignField] };
+        match[foreignField] = { ...trusted({ $in: ids }), ...userSpecifiedMatch };
+      }
+    }
+  }
+
+  return match;
+};
+
+/**
+ * Optionally filter out invalid ids that don't conform to foreign field's schema
+ * to avoid cast errors (gh-7706)
+ * @param {Array} ids
+ * @param {SchemaType} foreignSchemaType
+ * @param {Boolean} [skipInvalidIds]
+ * @api private
+ */
+
+function _filterInvalidIds(ids, foreignSchemaType, skipInvalidIds) {
+  ids = ids.filter(v => !(v instanceof SkipPopulateValue));
+  if (!skipInvalidIds) {
+    return ids;
+  }
+  return ids.filter(id => {
+    try {
+      foreignSchemaType.cast(id);
+      return true;
+    } catch (err) {
+      return false;
+    }
+  });
+}
+
+/**
+ * Format `mod.match` given that it may be an array that we need to $or if
+ * the client has multiple docs with match functions
+ * @param {Array|Any} match
+ * @api private
+ */
+
+function _formatMatch(match) {
+  if (Array.isArray(match)) {
+    if (match.length > 1) {
+      return { $or: [].concat(match.map(m => Object.assign({}, m))) };
+    }
+    return Object.assign({}, match[0]);
+  }
+  return Object.assign({}, match);
+}

node_modules/mongoose/lib/helpers/populate/getModelsMapForPopulate.js

@@ -0,0 +1,733 @@
+'use strict';
+
+const MongooseError = require('../../error/index');
+const SkipPopulateValue = require('./SkipPopulateValue');
+const clone = require('../clone');
+const get = require('../get');
+const getDiscriminatorByValue = require('../discriminator/getDiscriminatorByValue');
+const getConstructorName = require('../getConstructorName');
+const getSchemaTypes = require('./getSchemaTypes');
+const getVirtual = require('./getVirtual');
+const lookupLocalFields = require('./lookupLocalFields');
+const mpath = require('mpath');
+const modelNamesFromRefPath = require('./modelNamesFromRefPath');
+const utils = require('../../utils');
+
+const modelSymbol = require('../symbols').modelSymbol;
+const populateModelSymbol = require('../symbols').populateModelSymbol;
+const schemaMixedSymbol = require('../../schema/symbols').schemaMixedSymbol;
+const StrictPopulate = require('../../error/strictPopulate');
+
+module.exports = function getModelsMapForPopulate(model, docs, options) {
+  let doc;
+  const len = docs.length;
+  const map = [];
+  const modelNameFromQuery = options.model && options.model.modelName || options.model;
+  let schema;
+  let refPath;
+  let modelNames;
+  const available = {};
+
+  const modelSchema = model.schema;
+
+  // Populating a nested path should always be a no-op re: #9073.
+  // People shouldn't do this, but apparently they do.
+  if (options._localModel != null && options._localModel.schema.nested[options.path]) {
+    return [];
+  }
+
+  const _virtualRes = getVirtual(model.schema, options.path);
+  const virtual = _virtualRes == null ? null : _virtualRes.virtual;
+  if (virtual != null) {
+    return _virtualPopulate(model, docs, options, _virtualRes);
+  }
+
+  let allSchemaTypes = getSchemaTypes(model, modelSchema, null, options.path);
+  allSchemaTypes = Array.isArray(allSchemaTypes) ? allSchemaTypes : [allSchemaTypes].filter(v => v != null);
+
+  if (allSchemaTypes.length === 0 && options.strictPopulate !== false && options._localModel != null) {
+    return new StrictPopulate(options._fullPath || options.path);
+  }
+
+  for (let i = 0; i < len; i++) {
+    doc = docs[i];
+    let justOne = null;
+
+    const docSchema = doc != null && doc.$__ != null ? doc.$__schema : modelSchema;
+    schema = getSchemaTypes(model, docSchema, doc, options.path);
+
+    // Special case: populating a path that's a DocumentArray unless
+    // there's an explicit `ref` or `refPath` re: gh-8946
+    if (schema != null &&
+        schema.$isMongooseDocumentArray &&
+        schema.options.ref == null &&
+        schema.options.refPath == null) {
+      continue;
+    }
+    const isUnderneathDocArray = schema && schema.$isUnderneathDocArray;
+    if (isUnderneathDocArray && get(options, 'options.sort') != null) {
+      return new MongooseError('Cannot populate with `sort` on path ' + options.path +
+        ' because it is a subproperty of a document array');
+    }
+
+    modelNames = null;
+    let isRefPath = false;
+    let normalizedRefPath = null;
+    let schemaOptions = null;
+    let modelNamesInOrder = null;
+
+    if (schema != null && schema.instance === 'Embedded') {
+      if (schema.options.ref) {
+        const data = {
+          localField: options.path + '._id',
+          foreignField: '_id',
+          justOne: true
+        };
+        const res = _getModelNames(doc, schema, modelNameFromQuery, model);
+
+        const unpopulatedValue = mpath.get(options.path, doc);
+        const id = mpath.get('_id', unpopulatedValue);
+        addModelNamesToMap(model, map, available, res.modelNames, options, data, id, doc, schemaOptions, unpopulatedValue);
+      }
+      // No-op if no `ref` set. See gh-11538
+      continue;
+    }
+
+    if (Array.isArray(schema)) {
+      const schemasArray = schema;
+      for (const _schema of schemasArray) {
+        let _modelNames;
+        let res;
+        try {
+          res = _getModelNames(doc, _schema, modelNameFromQuery, model);
+          _modelNames = res.modelNames;
+          isRefPath = isRefPath || res.isRefPath;
+          normalizedRefPath = normalizedRefPath || res.refPath;
+          justOne = res.justOne;
+        } catch (error) {
+          return error;
+        }
+
+        if (isRefPath && !res.isRefPath) {
+          continue;
+        }
+        if (!_modelNames) {
+          continue;
+        }
+        modelNames = modelNames || [];
+        for (const modelName of _modelNames) {
+          if (modelNames.indexOf(modelName) === -1) {
+            modelNames.push(modelName);
+          }
+        }
+      }
+    } else {
+      try {
+        const res = _getModelNames(doc, schema, modelNameFromQuery, model);
+        modelNames = res.modelNames;
+        isRefPath = res.isRefPath;
+        normalizedRefPath = normalizedRefPath || res.refPath;
+        justOne = res.justOne;
+        schemaOptions = get(schema, 'options.populate', null);
+        // Dedupe, because `refPath` can return duplicates of the same model name,
+        // and that causes perf issues.
+        if (isRefPath) {
+          modelNamesInOrder = modelNames;
+          modelNames = Array.from(new Set(modelNames));
+        }
+      } catch (error) {
+        return error;
+      }
+
+      if (!modelNames) {
+        continue;
+      }
+    }
+
+    const data = {};
+    const localField = options.path;
+    const foreignField = '_id';
+
+    // `justOne = null` means we don't know from the schema whether the end
+    // result should be an array or a single doc. This can result from
+    // populating a POJO using `Model.populate()`
+    if ('justOne' in options && options.justOne !== void 0) {
+      justOne = options.justOne;
+    } else if (schema && !schema[schemaMixedSymbol]) {
+      // Skip Mixed types because we explicitly don't do casting on those.
+      if (options.path.endsWith('.' + schema.path) || options.path === schema.path) {
+        justOne = Array.isArray(schema) ?
+          schema.every(schema => !schema.$isMongooseArray) :
+          !schema.$isMongooseArray;
+      }
+    }
+
+    if (!modelNames) {
+      continue;
+    }
+
+    data.isVirtual = false;
+    data.justOne = justOne;
+    data.localField = localField;
+    data.foreignField = foreignField;
+
+    // Get local fields
+    const ret = _getLocalFieldValues(doc, localField, model, options, null, schema);
+
+    const id = String(utils.getValue(foreignField, doc));
+    options._docs[id] = Array.isArray(ret) ? ret.slice() : ret;
+
+    let match = get(options, 'match', null);
+
+    const hasMatchFunction = typeof match === 'function';
+    if (hasMatchFunction) {
+      match = match.call(doc, doc);
+    }
+    data.match = match;
+    data.hasMatchFunction = hasMatchFunction;
+    data.isRefPath = isRefPath;
+    data.modelNamesInOrder = modelNamesInOrder;
+
+    if (isRefPath) {
+      const embeddedDiscriminatorModelNames = _findRefPathForDiscriminators(doc,
+        modelSchema, data, options, normalizedRefPath, ret);
+
+      modelNames = embeddedDiscriminatorModelNames || modelNames;
+    }
+
+    try {
+      addModelNamesToMap(model, map, available, modelNames, options, data, ret, doc, schemaOptions);
+    } catch (err) {
+      return err;
+    }
+  }
+  return map;
+
+  function _getModelNames(doc, schema, modelNameFromQuery, model) {
+    let modelNames;
+    let isRefPath = false;
+    let justOne = null;
+
+    const originalSchema = schema;
+    if (schema && schema.instance === 'Array') {
+      schema = schema.caster;
+    }
+    if (schema && schema.$isSchemaMap) {
+      schema = schema.$__schemaType;
+    }
+
+    const ref = schema && schema.options && schema.options.ref;
+    refPath = schema && schema.options && schema.options.refPath;
+    if (schema != null &&
+        schema[schemaMixedSymbol] &&
+        !ref &&
+        !refPath &&
+        !modelNameFromQuery) {
+      return { modelNames: null };
+    }
+
+    if (modelNameFromQuery) {
+      modelNames = [modelNameFromQuery]; // query options
+    } else if (refPath != null) {
+      if (typeof refPath === 'function') {
+        const subdocPath = options.path.slice(0, options.path.length - schema.path.length - 1);
+        const vals = mpath.get(subdocPath, doc, lookupLocalFields);
+        const subdocsBeingPopulated = Array.isArray(vals) ?
+          utils.array.flatten(vals) :
+          (vals ? [vals] : []);
+
+        modelNames = new Set();
+        for (const subdoc of subdocsBeingPopulated) {
+          refPath = refPath.call(subdoc, subdoc, options.path);
+          modelNamesFromRefPath(refPath, doc, options.path, modelSchema, options._queryProjection).
+            forEach(name => modelNames.add(name));
+        }
+        modelNames = Array.from(modelNames);
+      } else {
+        modelNames = modelNamesFromRefPath(refPath, doc, options.path, modelSchema, options._queryProjection);
+      }
+
+      isRefPath = true;
+    } else {
+      let ref;
+      let refPath;
+      let schemaForCurrentDoc;
+      let discriminatorValue;
+      let modelForCurrentDoc = model;
+      const discriminatorKey = model.schema.options.discriminatorKey;
+
+      if (!schema && discriminatorKey && (discriminatorValue = utils.getValue(discriminatorKey, doc))) {
+        // `modelNameForFind` is the discriminator value, so we might need
+        // find the discriminated model name
+        const discriminatorModel = getDiscriminatorByValue(model.discriminators, discriminatorValue) || model;
+        if (discriminatorModel != null) {
+          modelForCurrentDoc = discriminatorModel;
+        } else {
+          try {
+            modelForCurrentDoc = _getModelFromConn(model.db, discriminatorValue);
+          } catch (error) {
+            return error;
+          }
+        }
+
+        schemaForCurrentDoc = modelForCurrentDoc.schema._getSchema(options.path);
+
+        if (schemaForCurrentDoc && schemaForCurrentDoc.caster) {
+          schemaForCurrentDoc = schemaForCurrentDoc.caster;
+        }
+      } else {
+        schemaForCurrentDoc = schema;
+      }
+
+      if (originalSchema && originalSchema.path.endsWith('.$*')) {
+        justOne = !originalSchema.$isMongooseArray && !originalSchema._arrayPath;
+      } else if (schemaForCurrentDoc != null) {
+        justOne = !schemaForCurrentDoc.$isMongooseArray && !schemaForCurrentDoc._arrayPath;
+      }
+
+      if ((ref = get(schemaForCurrentDoc, 'options.ref')) != null) {
+        if (schemaForCurrentDoc != null &&
+            typeof ref === 'function' &&
+            options.path.endsWith('.' + schemaForCurrentDoc.path)) {
+          // Ensure correct context for ref functions: subdoc, not top-level doc. See gh-8469
+          modelNames = new Set();
+
+          const subdocPath = options.path.slice(0, options.path.length - schemaForCurrentDoc.path.length - 1);
+          const vals = mpath.get(subdocPath, doc, lookupLocalFields);
+          const subdocsBeingPopulated = Array.isArray(vals) ?
+            utils.array.flatten(vals) :
+            (vals ? [vals] : []);
+          for (const subdoc of subdocsBeingPopulated) {
+            modelNames.add(handleRefFunction(ref, subdoc));
+          }
+
+          if (subdocsBeingPopulated.length === 0) {
+            modelNames = [handleRefFunction(ref, doc)];
+          } else {
+            modelNames = Array.from(modelNames);
+          }
+        } else {
+          ref = handleRefFunction(ref, doc);
+          modelNames = [ref];
+        }
+      } else if ((schemaForCurrentDoc = get(schema, 'options.refPath')) != null) {
+        isRefPath = true;
+        if (typeof refPath === 'function') {
+          const subdocPath = options.path.slice(0, options.path.length - schemaForCurrentDoc.path.length - 1);
+          const vals = mpath.get(subdocPath, doc, lookupLocalFields);
+          const subdocsBeingPopulated = Array.isArray(vals) ?
+            utils.array.flatten(vals) :
+            (vals ? [vals] : []);
+
+          modelNames = new Set();
+          for (const subdoc of subdocsBeingPopulated) {
+            refPath = refPath.call(subdoc, subdoc, options.path);
+            modelNamesFromRefPath(refPath, doc, options.path, modelSchema, options._queryProjection).
+              forEach(name => modelNames.add(name));
+          }
+          modelNames = Array.from(modelNames);
+        } else {
+          modelNames = modelNamesFromRefPath(refPath, doc, options.path, modelSchema, options._queryProjection);
+        }
+      }
+    }
+
+    if (!modelNames) {
+      // `Model.populate()` on a POJO with no known local model. Default to using the `Model`
+      if (options._localModel == null) {
+        modelNames = [model.modelName];
+      } else {
+        return { modelNames: modelNames, justOne: justOne, isRefPath: isRefPath, refPath: refPath };
+      }
+    }
+
+    if (!Array.isArray(modelNames)) {
+      modelNames = [modelNames];
+    }
+
+    return { modelNames: modelNames, justOne: justOne, isRefPath: isRefPath, refPath: refPath };
+  }
+};
+
+/*!
+ * ignore
+ */
+
+function _virtualPopulate(model, docs, options, _virtualRes) {
+  const map = [];
+  const available = {};
+  const virtual = _virtualRes.virtual;
+
+  for (const doc of docs) {
+    let modelNames = null;
+    const data = {};
+
+    // localField and foreignField
+    let localField;
+    const virtualPrefix = _virtualRes.nestedSchemaPath ?
+      _virtualRes.nestedSchemaPath + '.' : '';
+    if (typeof options.localField === 'string') {
+      localField = options.localField;
+    } else if (typeof virtual.options.localField === 'function') {
+      localField = virtualPrefix + virtual.options.localField.call(doc, doc);
+    } else if (Array.isArray(virtual.options.localField)) {
+      localField = virtual.options.localField.map(field => virtualPrefix + field);
+    } else {
+      localField = virtualPrefix + virtual.options.localField;
+    }
+    data.count = virtual.options.count;
+
+    if (virtual.options.skip != null && !options.hasOwnProperty('skip')) {
+      options.skip = virtual.options.skip;
+    }
+    if (virtual.options.limit != null && !options.hasOwnProperty('limit')) {
+      options.limit = virtual.options.limit;
+    }
+    if (virtual.options.perDocumentLimit != null && !options.hasOwnProperty('perDocumentLimit')) {
+      options.perDocumentLimit = virtual.options.perDocumentLimit;
+    }
+    let foreignField = virtual.options.foreignField;
+
+    if (!localField || !foreignField) {
+      return new MongooseError('If you are populating a virtual, you must set the ' +
+        'localField and foreignField options');
+    }
+
+    if (typeof localField === 'function') {
+      localField = localField.call(doc, doc);
+    }
+    if (typeof foreignField === 'function') {
+      foreignField = foreignField.call(doc, doc);
+    }
+
+    data.isRefPath = false;
+
+    // `justOne = null` means we don't know from the schema whether the end
+    // result should be an array or a single doc. This can result from
+    // populating a POJO using `Model.populate()`
+    let justOne = null;
+    if ('justOne' in options && options.justOne !== void 0) {
+      justOne = options.justOne;
+    }
+
+    if (virtual.options.refPath) {
+      modelNames =
+        modelNamesFromRefPath(virtual.options.refPath, doc, options.path);
+      justOne = !!virtual.options.justOne;
+      data.isRefPath = true;
+    } else if (virtual.options.ref) {
+      let normalizedRef;
+      if (typeof virtual.options.ref === 'function' && !virtual.options.ref[modelSymbol]) {
+        normalizedRef = virtual.options.ref.call(doc, doc);
+      } else {
+        normalizedRef = virtual.options.ref;
+      }
+      justOne = !!virtual.options.justOne;
+      // When referencing nested arrays, the ref should be an Array
+      // of modelNames.
+      if (Array.isArray(normalizedRef)) {
+        modelNames = normalizedRef;
+      } else {
+        modelNames = [normalizedRef];
+      }
+    }
+
+    data.isVirtual = true;
+    data.virtual = virtual;
+    data.justOne = justOne;
+
+    // `match`
+    let match = get(options, 'match', null) ||
+      get(data, 'virtual.options.match', null) ||
+      get(data, 'virtual.options.options.match', null);
+
+    let hasMatchFunction = typeof match === 'function';
+    if (hasMatchFunction) {
+      match = match.call(doc, doc);
+    }
+
+    if (Array.isArray(localField) && Array.isArray(foreignField) && localField.length === foreignField.length) {
+      match = Object.assign({}, match);
+      for (let i = 1; i < localField.length; ++i) {
+        match[foreignField[i]] = convertTo_id(mpath.get(localField[i], doc, lookupLocalFields), model.schema);
+        hasMatchFunction = true;
+      }
+
+      localField = localField[0];
+      foreignField = foreignField[0];
+    }
+    data.localField = localField;
+    data.foreignField = foreignField;
+    data.match = match;
+    data.hasMatchFunction = hasMatchFunction;
+
+    // Get local fields
+    const ret = _getLocalFieldValues(doc, localField, model, options, virtual);
+
+    try {
+      addModelNamesToMap(model, map, available, modelNames, options, data, ret, doc);
+    } catch (err) {
+      return err;
+    }
+  }
+
+  return map;
+}
+
+/*!
+ * ignore
+ */
+
+function addModelNamesToMap(model, map, available, modelNames, options, data, ret, doc, schemaOptions, unpopulatedValue) {
+  // `PopulateOptions#connection`: if the model is passed as a string, the
+  // connection matters because different connections have different models.
+  const connection = options.connection != null ? options.connection : model.db;
+
+  unpopulatedValue = unpopulatedValue === void 0 ? ret : unpopulatedValue;
+  if (Array.isArray(unpopulatedValue)) {
+    unpopulatedValue = utils.cloneArrays(unpopulatedValue);
+  }
+
+  if (modelNames == null) {
+    return;
+  }
+
+  let k = modelNames.length;
+  while (k--) {
+    const modelName = modelNames[k];
+    if (modelName == null) {
+      continue;
+    }
+
+    let Model;
+    if (options.model && options.model[modelSymbol]) {
+      Model = options.model;
+    } else if (modelName[modelSymbol]) {
+      Model = modelName;
+    } else {
+      try {
+        Model = _getModelFromConn(connection, modelName);
+      } catch (err) {
+        if (ret !== void 0) {
+          throw err;
+        }
+        Model = null;
+      }
+    }
+
+    let ids = ret;
+    const flat = Array.isArray(ret) ? utils.array.flatten(ret) : [];
+
+    const modelNamesForRefPath = data.modelNamesInOrder ? data.modelNamesInOrder : modelNames;
+    if (data.isRefPath && Array.isArray(ret) && flat.length === modelNamesForRefPath.length) {
+      ids = flat.filter((val, i) => modelNamesForRefPath[i] === modelName);
+    }
+
+    const perDocumentLimit = options.perDocumentLimit == null ?
+      get(options, 'options.perDocumentLimit', null) :
+      options.perDocumentLimit;
+
+    if (!available[modelName] || perDocumentLimit != null) {
+      const currentOptions = {
+        model: Model
+      };
+      if (data.isVirtual && get(data.virtual, 'options.options')) {
+        currentOptions.options = clone(data.virtual.options.options);
+      } else if (schemaOptions != null) {
+        currentOptions.options = Object.assign({}, schemaOptions);
+      }
+      utils.merge(currentOptions, options);
+
+      // Used internally for checking what model was used to populate this
+      // path.
+      options[populateModelSymbol] = Model;
+      available[modelName] = {
+        model: Model,
+        options: currentOptions,
+        match: data.hasMatchFunction ? [data.match] : data.match,
+        docs: [doc],
+        ids: [ids],
+        allIds: [ret],
+        unpopulatedValues: [unpopulatedValue],
+        localField: new Set([data.localField]),
+        foreignField: new Set([data.foreignField]),
+        justOne: data.justOne,
+        isVirtual: data.isVirtual,
+        virtual: data.virtual,
+        count: data.count,
+        [populateModelSymbol]: Model
+      };
+      map.push(available[modelName]);
+    } else {
+      available[modelName].localField.add(data.localField);
+      available[modelName].foreignField.add(data.foreignField);
+      available[modelName].docs.push(doc);
+      available[modelName].ids.push(ids);
+      available[modelName].allIds.push(ret);
+      available[modelName].unpopulatedValues.push(unpopulatedValue);
+      if (data.hasMatchFunction) {
+        available[modelName].match.push(data.match);
+      }
+    }
+  }
+}
+
+function _getModelFromConn(conn, modelName) {
+  /* If this connection has a parent from `useDb()`, bubble up to parent's models */
+  if (conn.models[modelName] == null && conn._parent != null) {
+    return _getModelFromConn(conn._parent, modelName);
+  }
+
+  return conn.model(modelName);
+}
+
+/*!
+ * ignore
+ */
+
+function handleRefFunction(ref, doc) {
+  if (typeof ref === 'function' && !ref[modelSymbol]) {
+    return ref.call(doc, doc);
+  }
+  return ref;
+}
+
+/*!
+ * ignore
+ */
+
+function _getLocalFieldValues(doc, localField, model, options, virtual, schema) {
+  // Get Local fields
+  const localFieldPathType = model.schema._getPathType(localField);
+  const localFieldPath = localFieldPathType === 'real' ?
+    model.schema.path(localField) :
+    localFieldPathType.schema;
+  const localFieldGetters = localFieldPath && localFieldPath.getters ?
+    localFieldPath.getters : [];
+
+  localField = localFieldPath != null && localFieldPath.instance === 'Embedded' ? localField + '._id' : localField;
+
+  const _populateOptions = get(options, 'options', {});
+
+  const getters = 'getters' in _populateOptions ?
+    _populateOptions.getters :
+    get(virtual, 'options.getters', false);
+  if (localFieldGetters.length !== 0 && getters) {
+    const hydratedDoc = (doc.$__ != null) ? doc : model.hydrate(doc);
+    const localFieldValue = utils.getValue(localField, doc);
+    if (Array.isArray(localFieldValue)) {
+      const localFieldHydratedValue = utils.getValue(localField.split('.').slice(0, -1), hydratedDoc);
+      return localFieldValue.map((localFieldArrVal, localFieldArrIndex) =>
+        localFieldPath.applyGetters(localFieldArrVal, localFieldHydratedValue[localFieldArrIndex]));
+    } else {
+      return localFieldPath.applyGetters(localFieldValue, hydratedDoc);
+    }
+  } else {
+    return convertTo_id(mpath.get(localField, doc, lookupLocalFields), schema);
+  }
+}
+
+/**
+ * Retrieve the _id of `val` if a Document or Array of Documents.
+ *
+ * @param {Array|Document|Any} val
+ * @param {Schema} schema
+ * @return {Array|Document|Any}
+ * @api private
+ */
+
+function convertTo_id(val, schema) {
+  if (val != null && val.$__ != null) {
+    return val._id;
+  }
+  if (val != null && val._id != null && (schema == null || !schema.$isSchemaMap)) {
+    return val._id;
+  }
+
+  if (Array.isArray(val)) {
+    const rawVal = val.__array != null ? val.__array : val;
+    for (let i = 0; i < rawVal.length; ++i) {
+      if (rawVal[i] != null && rawVal[i].$__ != null) {
+        rawVal[i] = rawVal[i]._id;
+      }
+    }
+    if (utils.isMongooseArray(val) && val.$schema()) {
+      return val.$schema()._castForPopulate(val, val.$parent());
+    }
+
+    return [].concat(val);
+  }
+
+  // `populate('map')` may be an object if populating on a doc that hasn't
+  // been hydrated yet
+  if (getConstructorName(val) === 'Object' &&
+      // The intent here is we should only flatten the object if we expect
+      // to get a Map in the end. Avoid doing this for mixed types.
+      (schema == null || schema[schemaMixedSymbol] == null)) {
+    const ret = [];
+    for (const key of Object.keys(val)) {
+      ret.push(val[key]);
+    }
+    return ret;
+  }
+  // If doc has already been hydrated, e.g. `doc.populate('map')`
+  // then `val` will already be a map
+  if (val instanceof Map) {
+    return Array.from(val.values());
+  }
+
+  return val;
+}
+
+/*!
+ * ignore
+ */
+
+function _findRefPathForDiscriminators(doc, modelSchema, data, options, normalizedRefPath, ret) {
+  // Re: gh-8452. Embedded discriminators may not have `refPath`, so clear
+  // out embedded discriminator docs that don't have a `refPath` on the
+  // populated path.
+  if (!data.isRefPath || normalizedRefPath == null) {
+    return;
+  }
+
+  const pieces = normalizedRefPath.split('.');
+  let cur = '';
+  let modelNames = void 0;
+  for (let i = 0; i < pieces.length; ++i) {
+    const piece = pieces[i];
+    cur = cur + (cur.length === 0 ? '' : '.') + piece;
+    const schematype = modelSchema.path(cur);
+    if (schematype != null &&
+        schematype.$isMongooseArray &&
+        schematype.caster.discriminators != null &&
+        Object.keys(schematype.caster.discriminators).length !== 0) {
+      const subdocs = utils.getValue(cur, doc);
+      const remnant = options.path.substring(cur.length + 1);
+      const discriminatorKey = schematype.caster.schema.options.discriminatorKey;
+      modelNames = [];
+      for (const subdoc of subdocs) {
+        const discriminatorName = utils.getValue(discriminatorKey, subdoc);
+        const discriminator = schematype.caster.discriminators[discriminatorName];
+        const discriminatorSchema = discriminator && discriminator.schema;
+        if (discriminatorSchema == null) {
+          continue;
+        }
+        const _path = discriminatorSchema.path(remnant);
+        if (_path == null || _path.options.refPath == null) {
+          const docValue = utils.getValue(data.localField.substring(cur.length + 1), subdoc);
+          ret.forEach((v, i) => {
+            if (v === docValue) {
+              ret[i] = SkipPopulateValue(v);
+            }
+          });
+          continue;
+        }
+        const modelName = utils.getValue(pieces.slice(i + 1).join('.'), subdoc);
+        modelNames.push(modelName);
+      }
+    }
+  }
+
+  return modelNames;
+}

node_modules/mongoose/lib/helpers/populate/getSchemaTypes.js

@@ -0,0 +1,233 @@
+'use strict';
+
+/*!
+ * ignore
+ */
+
+const Mixed = require('../../schema/mixed');
+const get = require('../get');
+const getDiscriminatorByValue = require('../discriminator/getDiscriminatorByValue');
+const leanPopulateMap = require('./leanPopulateMap');
+const mpath = require('mpath');
+
+const populateModelSymbol = require('../symbols').populateModelSymbol;
+
+/**
+ * Given a model and its schema, find all possible schema types for `path`,
+ * including searching through discriminators. If `doc` is specified, will
+ * use the doc's values for discriminator keys when searching, otherwise
+ * will search all discriminators.
+ *
+ * @param {Model} model
+ * @param {Schema} schema
+ * @param {Object} doc POJO
+ * @param {string} path
+ * @api private
+ */
+
+module.exports = function getSchemaTypes(model, schema, doc, path) {
+  const pathschema = schema.path(path);
+  const topLevelDoc = doc;
+  if (pathschema) {
+    return pathschema;
+  }
+
+  const discriminatorKey = schema.discriminatorMapping &&
+    schema.discriminatorMapping.key;
+  if (discriminatorKey && model != null) {
+    if (doc != null && doc[discriminatorKey] != null) {
+      const discriminator = getDiscriminatorByValue(model.discriminators, doc[discriminatorKey]);
+      schema = discriminator ? discriminator.schema : schema;
+    } else if (model.discriminators != null) {
+      return Object.keys(model.discriminators).reduce((arr, name) => {
+        const disc = model.discriminators[name];
+        return arr.concat(getSchemaTypes(disc, disc.schema, null, path));
+      }, []);
+    }
+  }
+
+  function search(parts, schema, subdoc, nestedPath) {
+    let p = parts.length + 1;
+    let foundschema;
+    let trypath;
+
+    while (p--) {
+      trypath = parts.slice(0, p).join('.');
+      foundschema = schema.path(trypath);
+      if (foundschema == null) {
+        continue;
+      }
+
+      if (foundschema.caster) {
+        // array of Mixed?
+        if (foundschema.caster instanceof Mixed) {
+          return foundschema.caster;
+        }
+
+        let schemas = null;
+        if (foundschema.schema != null && foundschema.schema.discriminators != null) {
+          const discriminators = foundschema.schema.discriminators;
+          const discriminatorKeyPath = trypath + '.' +
+            foundschema.schema.options.discriminatorKey;
+          const keys = subdoc ? mpath.get(discriminatorKeyPath, subdoc) || [] : [];
+          schemas = Object.keys(discriminators).
+            reduce(function(cur, discriminator) {
+              const tiedValue = discriminators[discriminator].discriminatorMapping.value;
+              if (doc == null || keys.indexOf(discriminator) !== -1 || keys.indexOf(tiedValue) !== -1) {
+                cur.push(discriminators[discriminator]);
+              }
+              return cur;
+            }, []);
+        }
+
+        // Now that we found the array, we need to check if there
+        // are remaining document paths to look up for casting.
+        // Also we need to handle array.$.path since schema.path
+        // doesn't work for that.
+        // If there is no foundschema.schema we are dealing with
+        // a path like array.$
+        if (p !== parts.length && foundschema.schema) {
+          let ret;
+          if (parts[p] === '$') {
+            if (p + 1 === parts.length) {
+              // comments.$
+              return foundschema;
+            }
+            // comments.$.comments.$.title
+            ret = search(
+              parts.slice(p + 1),
+              schema,
+              subdoc ? mpath.get(trypath, subdoc) : null,
+              nestedPath.concat(parts.slice(0, p))
+            );
+            if (ret) {
+              ret.$isUnderneathDocArray = ret.$isUnderneathDocArray ||
+                !foundschema.schema.$isSingleNested;
+            }
+            return ret;
+          }
+
+          if (schemas != null && schemas.length > 0) {
+            ret = [];
+            for (const schema of schemas) {
+              const _ret = search(
+                parts.slice(p),
+                schema,
+                subdoc ? mpath.get(trypath, subdoc) : null,
+                nestedPath.concat(parts.slice(0, p))
+              );
+              if (_ret != null) {
+                _ret.$isUnderneathDocArray = _ret.$isUnderneathDocArray ||
+                  !foundschema.schema.$isSingleNested;
+                if (_ret.$isUnderneathDocArray) {
+                  ret.$isUnderneathDocArray = true;
+                }
+                ret.push(_ret);
+              }
+            }
+            return ret;
+          } else {
+            ret = search(
+              parts.slice(p),
+              foundschema.schema,
+              subdoc ? mpath.get(trypath, subdoc) : null,
+              nestedPath.concat(parts.slice(0, p))
+            );
+
+            if (ret) {
+              ret.$isUnderneathDocArray = ret.$isUnderneathDocArray ||
+                !foundschema.schema.$isSingleNested;
+            }
+            return ret;
+          }
+        } else if (p !== parts.length &&
+            foundschema.$isMongooseArray &&
+            foundschema.casterConstructor.$isMongooseArray) {
+          // Nested arrays. Drill down to the bottom of the nested array.
+          let type = foundschema;
+          while (type.$isMongooseArray && !type.$isMongooseDocumentArray) {
+            type = type.casterConstructor;
+          }
+
+          const ret = search(
+            parts.slice(p),
+            type.schema,
+            null,
+            nestedPath.concat(parts.slice(0, p))
+          );
+          if (ret != null) {
+            return ret;
+          }
+
+          if (type.schema.discriminators) {
+            const discriminatorPaths = [];
+            for (const discriminatorName of Object.keys(type.schema.discriminators)) {
+              const _schema = type.schema.discriminators[discriminatorName] || type.schema;
+              const ret = search(parts.slice(p), _schema, null, nestedPath.concat(parts.slice(0, p)));
+              if (ret != null) {
+                discriminatorPaths.push(ret);
+              }
+            }
+            if (discriminatorPaths.length > 0) {
+              return discriminatorPaths;
+            }
+          }
+        }
+      } else if (foundschema.$isSchemaMap && foundschema.$__schemaType instanceof Mixed) {
+        return foundschema.$__schemaType;
+      }
+
+      const fullPath = nestedPath.concat([trypath]).join('.');
+      if (topLevelDoc != null && topLevelDoc.$__ && topLevelDoc.$populated(fullPath) && p < parts.length) {
+        const model = doc.$__.populated[fullPath].options[populateModelSymbol];
+        if (model != null) {
+          const ret = search(
+            parts.slice(p),
+            model.schema,
+            subdoc ? mpath.get(trypath, subdoc) : null,
+            nestedPath.concat(parts.slice(0, p))
+          );
+
+          if (ret) {
+            ret.$isUnderneathDocArray = ret.$isUnderneathDocArray ||
+              !model.schema.$isSingleNested;
+          }
+          return ret;
+        }
+      }
+
+      const _val = get(topLevelDoc, trypath);
+      if (_val != null) {
+        const model = Array.isArray(_val) && _val.length > 0 ?
+          leanPopulateMap.get(_val[0]) :
+          leanPopulateMap.get(_val);
+        // Populated using lean, `leanPopulateMap` value is the foreign model
+        const schema = model != null ? model.schema : null;
+        if (schema != null) {
+          const ret = search(
+            parts.slice(p),
+            schema,
+            subdoc ? mpath.get(trypath, subdoc) : null,
+            nestedPath.concat(parts.slice(0, p))
+          );
+
+          if (ret != null) {
+            ret.$isUnderneathDocArray = ret.$isUnderneathDocArray ||
+              !schema.$isSingleNested;
+            return ret;
+          }
+        }
+      }
+      return foundschema;
+    }
+  }
+  // look for arrays
+  const parts = path.split('.');
+  for (let i = 0; i < parts.length; ++i) {
+    if (parts[i] === '$') {
+      // Re: gh-5628, because `schema.path()` doesn't take $ into account.
+      parts[i] = '0';
+    }
+  }
+  return search(parts, schema, doc, []);
+};

node_modules/mongoose/lib/helpers/populate/getVirtual.js

@@ -0,0 +1,72 @@
+'use strict';
+
+module.exports = getVirtual;
+
+/*!
+ * ignore
+ */
+
+function getVirtual(schema, name) {
+  if (schema.virtuals[name]) {
+    return { virtual: schema.virtuals[name], path: void 0 };
+  }
+
+  const parts = name.split('.');
+  let cur = '';
+  let nestedSchemaPath = '';
+  for (let i = 0; i < parts.length; ++i) {
+    cur += (cur.length > 0 ? '.' : '') + parts[i];
+    if (schema.virtuals[cur]) {
+      if (i === parts.length - 1) {
+        return { virtual: schema.virtuals[cur], path: nestedSchemaPath };
+      }
+      continue;
+    }
+
+    if (schema.nested[cur]) {
+      continue;
+    }
+
+    if (schema.paths[cur] && schema.paths[cur].schema) {
+      schema = schema.paths[cur].schema;
+      const rest = parts.slice(i + 1).join('.');
+
+      if (schema.virtuals[rest]) {
+        if (i === parts.length - 2) {
+          return {
+            virtual: schema.virtuals[rest],
+            nestedSchemaPath: [nestedSchemaPath, cur].filter(v => !!v).join('.')
+          };
+        }
+        continue;
+      }
+
+      if (i + 1 < parts.length && schema.discriminators) {
+        for (const key of Object.keys(schema.discriminators)) {
+          const res = getVirtual(schema.discriminators[key], rest);
+          if (res != null) {
+            const _path = [nestedSchemaPath, cur, res.nestedSchemaPath].
+              filter(v => !!v).join('.');
+            return {
+              virtual: res.virtual,
+              nestedSchemaPath: _path
+            };
+          }
+        }
+      }
+
+      nestedSchemaPath += (nestedSchemaPath.length > 0 ? '.' : '') + cur;
+      cur = '';
+      continue;
+    }
+
+    if (schema.discriminators) {
+      for (const discriminatorKey of Object.keys(schema.discriminators)) {
+        const virtualFromDiscriminator = getVirtual(schema.discriminators[discriminatorKey], name);
+        if (virtualFromDiscriminator) return virtualFromDiscriminator;
+      }
+    }
+
+    return null;
+  }
+}

node_modules/mongoose/lib/helpers/populate/leanPopulateMap.js

@@ -0,0 +1,7 @@
+'use strict';
+
+/*!
+ * ignore
+ */
+
+module.exports = new WeakMap();

node_modules/mongoose/lib/helpers/populate/lookupLocalFields.js

@@ -0,0 +1,40 @@
+'use strict';
+
+module.exports = function lookupLocalFields(cur, path, val) {
+  if (cur == null) {
+    return cur;
+  }
+
+  if (cur._doc != null) {
+    cur = cur._doc;
+  }
+
+  if (arguments.length >= 3) {
+    if (typeof cur !== 'object') {
+      return void 0;
+    }
+    if (val === void 0) {
+      return void 0;
+    }
+    if (cur instanceof Map) {
+      cur.set(path, val);
+    } else {
+      cur[path] = val;
+    }
+    return val;
+  }
+
+
+  // Support populating paths under maps using `map.$*.subpath`
+  if (path === '$*') {
+    return cur instanceof Map ?
+      Array.from(cur.values()) :
+      Object.keys(cur).map(key => cur[key]);
+  }
+
+  if (cur instanceof Map) {
+    return cur.get(path);
+  }
+
+  return cur[path];
+};

node_modules/mongoose/lib/helpers/populate/markArraySubdocsPopulated.js

@@ -0,0 +1,47 @@
+'use strict';
+
+const utils = require('../../utils');
+
+/**
+ * If populating a path within a document array, make sure each
+ * subdoc within the array knows its subpaths are populated.
+ *
+ * #### Example:
+ *
+ *     const doc = await Article.findOne().populate('comments.author');
+ *     doc.comments[0].populated('author'); // Should be set
+ *
+ * @param {Document} doc
+ * @param {Object} [populated]
+ * @api private
+ */
+
+module.exports = function markArraySubdocsPopulated(doc, populated) {
+  if (doc._id == null || populated == null || populated.length === 0) {
+    return;
+  }
+
+  const id = String(doc._id);
+  for (const item of populated) {
+    if (item.isVirtual) {
+      continue;
+    }
+    const path = item.path;
+    const pieces = path.split('.');
+    for (let i = 0; i < pieces.length - 1; ++i) {
+      const subpath = pieces.slice(0, i + 1).join('.');
+      const rest = pieces.slice(i + 1).join('.');
+      const val = doc.get(subpath);
+      if (val == null) {
+        continue;
+      }
+
+      if (utils.isMongooseDocumentArray(val)) {
+        for (let j = 0; j < val.length; ++j) {
+          val[j].populated(rest, item._docs[id] == null ? void 0 : item._docs[id][j], item);
+        }
+        break;
+      }
+    }
+  }
+};

node_modules/mongoose/lib/helpers/populate/modelNamesFromRefPath.js

@@ -0,0 +1,68 @@
+'use strict';
+
+const MongooseError = require('../../error/mongooseError');
+const isPathExcluded = require('../projection/isPathExcluded');
+const lookupLocalFields = require('./lookupLocalFields');
+const mpath = require('mpath');
+const util = require('util');
+const utils = require('../../utils');
+
+const hasNumericPropRE = /(\.\d+$|\.\d+\.)/g;
+
+module.exports = function modelNamesFromRefPath(refPath, doc, populatedPath, modelSchema, queryProjection) {
+  if (refPath == null) {
+    return [];
+  }
+
+  if (typeof refPath === 'string' && queryProjection != null && isPathExcluded(queryProjection, refPath)) {
+    throw new MongooseError('refPath `' + refPath + '` must not be excluded in projection, got ' +
+      util.inspect(queryProjection));
+  }
+
+  // If populated path has numerics, the end `refPath` should too. For example,
+  // if populating `a.0.b` instead of `a.b` and `b` has `refPath = a.c`, we
+  // should return `a.0.c` for the refPath.
+
+  if (hasNumericPropRE.test(populatedPath)) {
+    const chunks = populatedPath.split(hasNumericPropRE);
+
+    if (chunks[chunks.length - 1] === '') {
+      throw new Error('Can\'t populate individual element in an array');
+    }
+
+    let _refPath = '';
+    let _remaining = refPath;
+    // 2nd, 4th, etc. will be numeric props. For example: `[ 'a', '.0.', 'b' ]`
+    for (let i = 0; i < chunks.length; i += 2) {
+      const chunk = chunks[i];
+      if (_remaining.startsWith(chunk + '.')) {
+        _refPath += _remaining.substring(0, chunk.length) + chunks[i + 1];
+        _remaining = _remaining.substring(chunk.length + 1);
+      } else if (i === chunks.length - 1) {
+        _refPath += _remaining;
+        _remaining = '';
+        break;
+      } else {
+        throw new Error('Could not normalize ref path, chunk ' + chunk + ' not in populated path');
+      }
+    }
+
+    const refValue = mpath.get(_refPath, doc, lookupLocalFields);
+    let modelNames = Array.isArray(refValue) ? refValue : [refValue];
+    modelNames = utils.array.flatten(modelNames);
+    return modelNames;
+  }
+
+  const refValue = mpath.get(refPath, doc, lookupLocalFields);
+
+  let modelNames;
+  if (modelSchema != null && modelSchema.virtuals.hasOwnProperty(refPath)) {
+    modelNames = [modelSchema.virtuals[refPath].applyGetters(void 0, doc)];
+  } else {
+    modelNames = Array.isArray(refValue) ? refValue : [refValue];
+  }
+
+  modelNames = utils.array.flatten(modelNames);
+
+  return modelNames;
+};

node_modules/mongoose/lib/helpers/populate/removeDeselectedForeignField.js

@@ -0,0 +1,31 @@
+'use strict';
+
+const get = require('../get');
+const mpath = require('mpath');
+const parseProjection = require('../projection/parseProjection');
+
+/*!
+ * ignore
+ */
+
+module.exports = function removeDeselectedForeignField(foreignFields, options, docs) {
+  const projection = parseProjection(get(options, 'select', null), true) ||
+    parseProjection(get(options, 'options.select', null), true);
+
+  if (projection == null) {
+    return;
+  }
+  for (const foreignField of foreignFields) {
+    if (!projection.hasOwnProperty('-' + foreignField)) {
+      continue;
+    }
+
+    for (const val of docs) {
+      if (val.$__ != null) {
+        mpath.unset(foreignField, val._doc);
+      } else {
+        mpath.unset(foreignField, val);
+      }
+    }
+  }
+};

node_modules/mongoose/lib/helpers/populate/validateRef.js

@@ -0,0 +1,19 @@
+'use strict';
+
+const MongooseError = require('../../error/mongooseError');
+const util = require('util');
+
+module.exports = validateRef;
+
+function validateRef(ref, path) {
+  if (typeof ref === 'string') {
+    return;
+  }
+
+  if (typeof ref === 'function') {
+    return;
+  }
+
+  throw new MongooseError('Invalid ref at path "' + path + '". Got ' +
+    util.inspect(ref, { depth: 0 }));
+}