From e2d191aa8a07c965123e3ab7d1c989c9c1f917d3 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Sun, 22 Sep 2019 21:06:31 -0700
Subject: [PATCH] fix(discriminator): support `tiedValue` parameter for
 embedded discriminators analagous to top-level discriminators

Fix #8164
---
 lib/schema/SingleNestedPath.js   |  4 ++--
 lib/schema/documentarray.js      |  4 ++--
 test/model.discriminator.test.js | 40 ++++++++++++++++++++++++++++++++
 3 files changed, 44 insertions(+), 4 deletions(-)

diff --git a/lib/schema/SingleNestedPath.js b/lib/schema/SingleNestedPath.js
index 9a2142f4159..3862529619c 100644
--- a/lib/schema/SingleNestedPath.js
+++ b/lib/schema/SingleNestedPath.js
@@ -283,8 +283,8 @@ SingleNestedPath.prototype.doValidateSync = function(value, scope, options) {
  * @api public
  */
 
-SingleNestedPath.prototype.discriminator = function(name, schema) {
-  discriminator(this.caster, name, schema);
+SingleNestedPath.prototype.discriminator = function(name, schema, tiedValue) {
+  discriminator(this.caster, name, schema, tiedValue);
 
   this.caster.discriminators[name] = _createConstructor(schema, this.caster);
 
diff --git a/lib/schema/documentarray.js b/lib/schema/documentarray.js
index cce9026d776..9229676f77d 100644
--- a/lib/schema/documentarray.js
+++ b/lib/schema/documentarray.js
@@ -126,12 +126,12 @@ function _createConstructor(schema, options, baseClass) {
  * Ignore
  */
 
-DocumentArray.prototype.discriminator = function(name, schema) {
+DocumentArray.prototype.discriminator = function(name, schema, tiedValue) {
   if (typeof name === 'function') {
     name = utils.getFunctionName(name);
   }
 
-  schema = discriminator(this.casterConstructor, name, schema);
+  schema = discriminator(this.casterConstructor, name, schema, tiedValue);
 
   const EmbeddedDocument = _createConstructor(schema, null, this.casterConstructor);
   EmbeddedDocument.baseCasterConstructor = this.casterConstructor;
diff --git a/test/model.discriminator.test.js b/test/model.discriminator.test.js
index 0155ad61824..eb25e0a3939 100644
--- a/test/model.discriminator.test.js
+++ b/test/model.discriminator.test.js
@@ -1080,6 +1080,46 @@ describe('model', function() {
         catch(done);
     });
 
+    it('embedded with single nested subdocs and tied value (gh-8164)', function() {
+      const eventSchema = new Schema({ message: String },
+        { discriminatorKey: 'kind', _id: false });
+
+        const trackSchema = new Schema({ event: eventSchema });
+      trackSchema.path('event').discriminator('Clicked', new Schema({
+        element: String
+      }, { _id: false }), 'click');
+      trackSchema.path('event').discriminator('Purchased', new Schema({
+        product: String
+      }, { _id: false }), 'purchase');
+
+      const MyModel = db.model('gh8164', trackSchema);
+      const doc1 = {
+        event: {
+          kind: 'click',
+          element: 'Amazon Link'
+        }
+      };
+      const doc2 = {
+        event: {
+          kind: 'purchase',
+          product: 'Professional AngularJS'
+        }
+      };
+      return MyModel.create([doc1, doc2]).
+        then(function(docs) {
+          const doc1 = docs[0];
+          const doc2 = docs[1];
+
+          assert.equal(doc1.event.kind, 'click');
+          assert.equal(doc1.event.element, 'Amazon Link');
+          assert.ok(!doc1.event.product);
+
+          assert.equal(doc2.event.kind, 'purchase');
+          assert.equal(doc2.event.product, 'Professional AngularJS');
+          assert.ok(!doc2.event.element);
+        });
+    });
+
     it('Embedded discriminators in nested doc arrays (gh-6202)', function() {
       const eventSchema = new Schema({ message: String }, {
         discriminatorKey: 'kind',