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'use strict';const assert = require('assert');const mongoose = require('../../lib');const Schema = mongoose.Schema;const ObjectId = mongoose.Types.ObjectId;
/** * Connect to the db */
const dbname = 'testing_populateAdInfinitum_' + require('../../lib/utils').random();mongoose.connect('localhost', dbname);mongoose.connection.on('error', function() {  console.error('connection error', arguments);});
/** * Schemas */
const user = new Schema({  name: String,  friends: [{    type: Schema.ObjectId,    ref: 'User'  }]});const User = mongoose.model('User', user);
const blogpost = Schema({  title: String,  tags: [String],  author: {    type: Schema.ObjectId,    ref: 'User'  }});const BlogPost = mongoose.model('BlogPost', blogpost);
/** * example */
mongoose.connection.on('open', function() {  /**   * Generate data   */
  const userIds = [new ObjectId(), new ObjectId(), new ObjectId(), new ObjectId()];  const users = [];
  users.push({    _id: userIds[0],    name: 'mary',    friends: [userIds[1], userIds[2], userIds[3]]  });  users.push({    _id: userIds[1],    name: 'bob',    friends: [userIds[0], userIds[2], userIds[3]]  });  users.push({    _id: userIds[2],    name: 'joe',    friends: [userIds[0], userIds[1], userIds[3]]  });  users.push({    _id: userIds[3],    name: 'sally',    friends: [userIds[0], userIds[1], userIds[2]]  });
  User.create(users, function(err) {    assert.ifError(err);
    const blogposts = [];    blogposts.push({      title: 'blog 1',      tags: ['fun', 'cool'],      author: userIds[3]    });    blogposts.push({      title: 'blog 2',      tags: ['cool'],      author: userIds[1]    });    blogposts.push({      title: 'blog 3',      tags: ['fun', 'odd'],      author: userIds[2]    });
    BlogPost.create(blogposts, function(err) {      assert.ifError(err);
      /**       * Population       */
      BlogPost        .find({ tags: 'fun' })        .lean()        .populate('author')        .exec(function(err, docs) {          assert.ifError(err);
          /**         * Populate the populated documents         */
          const opts = {            path: 'author.friends',            select: 'name',            options: { limit: 2 }          };
          BlogPost.populate(docs, opts, function(err, docs) {            assert.ifError(err);            console.log('populated');            const s = require('util').inspect(docs, { depth: null, colors: true });            console.log(s);            done();          });        });    });  });});
function done(err) {  if (err) console.error(err.stack);  mongoose.connection.db.dropDatabase(function() {    mongoose.connection.close();  });}