From 1b190b63f6067e950a385b900e94d7ad0ec2b3d6 Mon Sep 17 00:00:00 2001
From: Jeremy Philippe <jeremy.philippe@gmail.com>
Date: Sat, 16 May 2020 12:32:30 +0200
Subject: [PATCH] fix(documentarray): make sure you can call `unshift()` after
 `map()`

Fix #9012
---
 lib/types/core_array.js          | 12 +++++++++---
 test/types.documentarray.test.js | 21 +++++++++++++++++++++
 2 files changed, 30 insertions(+), 3 deletions(-)

diff --git a/lib/types/core_array.js b/lib/types/core_array.js
index b6632359daa..c4c6b33b441 100644
--- a/lib/types/core_array.js
+++ b/lib/types/core_array.js
@@ -879,7 +879,7 @@ class CoreMongooseArray extends Array {
    *
    * ####Note:
    *
-   * _marks the entire array as modified, which if saved, will store it as a `$set` operation, potentially overwritting any changes that happen between when you retrieved the object and when you save it._
+   * _marks the entire array as modified, which if saved, will store it as a `$set` operation, potentially overwriting any changes that happen between when you retrieved the object and when you save it._
    *
    * @api public
    * @method unshift
@@ -889,8 +889,14 @@ class CoreMongooseArray extends Array {
   unshift() {
     _checkManualPopulation(this, arguments);
 
-    let values = [].map.call(arguments, this._cast, this);
-    values = this[arraySchemaSymbol].applySetters(values, this[arrayParentSymbol]);
+    let values;
+    if (this[arraySchemaSymbol] == null) {
+      values = arguments;
+    } else {
+      values = [].map.call(arguments, this._cast, this);
+      values = this[arraySchemaSymbol].applySetters(values, this[arrayParentSymbol]);
+    }
+
     [].unshift.apply(this, values);
     this._registerAtomic('$set', this);
     this._markModified();
diff --git a/test/types.documentarray.test.js b/test/types.documentarray.test.js
index 22d9db368a9..93bafeccaa8 100644
--- a/test/types.documentarray.test.js
+++ b/test/types.documentarray.test.js
@@ -611,6 +611,27 @@ describe('types.documentarray', function() {
         'd'
       ]);
     });
+
+    it('unshift() after map() works (gh-9012)', function() {
+      const MyModel = db.model('Test', Schema({
+        myArray: [{ name: String }]
+      }));
+
+      const doc = new MyModel({
+        myArray: [{ name: 'b' }, { name: 'c' }]
+      });
+      let myArray = doc.myArray;
+
+      myArray = myArray.map(val => ({ name: `${val.name} mapped` }));
+
+      myArray.unshift({ name: 'a inserted' });
+
+      assert.deepEqual(myArray.map(v => v.name), [
+        'a inserted',
+        'b mapped',
+        'c mapped'
+      ]);
+    });
   });
 
   it('cleans modified subpaths on splice() (gh-7249)', function() {