fix(schema): correctly handle uuids with populate()

lib/schema/uuid.js

@@ -8,7 +8,6 @@ const MongooseBuffer = require('../types/buffer');
 const SchemaType = require('../schematype');
 const CastError = SchemaType.CastError;
 const utils = require('../utils');
-const isBsonType = require('../helpers/isBsonType');
 const handleBitwiseOperator = require('./operators/bitwise');
 
 const UUID_FORMAT = /[0-9a-f]{8}-[0-9a-f]{4}-[0-9][0-9a-f]{3}-[89ab][0-9a-f]{3}-[0-9a-f]{12}/i;
@@ -86,7 +85,13 @@ function binaryToString(uuidBin) {
 
 function SchemaUUID(key, options) {
   SchemaType.call(this, key, options, 'UUID');
-  this.getters.push(binaryToString);
+  this.getters.push(function(value) {
+    // For populated
+    if (value != null && value.$__ != null) {
+      return value;
+    }
+    return binaryToString(value);
+  });
 }
 
 /**
@@ -110,7 +115,7 @@ SchemaUUID.prototype.constructor = SchemaUUID;
  */
 
 SchemaUUID._cast = function(value) {
-  if (value === null) {
+  if (value == null) {
     return value;
   }
 
@@ -247,11 +252,8 @@ SchemaUUID.prototype.checkRequired = function checkRequired(value) {
  */
 
 SchemaUUID.prototype.cast = function(value, doc, init) {
-  if (SchemaType._isRef(this, value, doc, init)) {
-    if (isBsonType(value, 'UUID')) {
-      return value;
-    }
-
+  if (utils.isNonBuiltinObject(value) &&
+      SchemaType._isRef(this, value, doc, init)) {
     return this._castRef(value, doc, init);
   }
 

lib/schematype.js

@@ -1522,6 +1522,7 @@ SchemaType.prototype._castRef = function _castRef(value, doc, init) {
   const path = doc.$__fullPath(this.path, true);
   const owner = doc.ownerDocument();
   const pop = owner.$populated(path, true);
+
   let ret = value;
   if (!doc.$__.populated ||
     !doc.$__.populated[path] ||

lib/utils.js

@@ -4,6 +4,7 @@
  * Module dependencies.
  */
 
+const UUID = require('bson').UUID;
 const ms = require('ms');
 const mpath = require('mpath');
 const ObjectId = require('./types/objectid');
@@ -395,6 +396,7 @@ exports.isNonBuiltinObject = function isNonBuiltinObject(val) {
   return typeof val === 'object' &&
     !exports.isNativeObject(val) &&
     !exports.isMongooseType(val) &&
+    !(val instanceof UUID) &&
     val != null;
 };
 

test/schema.uuid.test.js

@@ -3,9 +3,9 @@
 const start = require('./common');
 const util = require('./util');
 
-const bson = require('bson');
-
 const assert = require('assert');
+const bson = require('bson');
+const { randomUUID } = require('crypto');
 
 const mongoose = start.mongoose;
 const Schema = mongoose.Schema;
@@ -129,6 +129,27 @@ describe('SchemaUUID', function() {
     assert.equal(organization, undefined);
   });
 
+  it('works with populate (gh-13267)', async function() {
+    const userSchema = new mongoose.Schema({
+      _id: { type: 'UUID', default: () => randomUUID() },
+      name: String,
+      createdBy: {
+        type: 'UUID',
+        ref: 'User'
+      }
+    });
+    const User = db.model('User', userSchema);
+
+    const u1 = await User.create({ name: 'admin' });
+    const { _id } = await User.create({ name: 'created', createdBy: u1._id });
+
+    const pop = await User.findById(_id).populate('createdBy').orFail();
+    assert.equal(pop.createdBy.name, 'admin');
+    assert.equal(pop.createdBy._id.toString(), u1._id.toString());
+
+    await pop.save();
+  });
+
   // the following are TODOs based on SchemaUUID.prototype.$conditionalHandlers which are not tested yet
   it('should work with $bits* operators');
   it('should work with $all operator');