From 6c1dcb28cc6eb528a3710f64fe3cc95ea7e628ff Mon Sep 17 00:00:00 2001
From: Hafez <a.hafez852@gmail.com>
Date: Wed, 13 Nov 2019 15:50:42 +0200
Subject: [PATCH 1/2] Fixes #8331

---
 lib/helpers/model/castBulkWrite.js | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/lib/helpers/model/castBulkWrite.js b/lib/helpers/model/castBulkWrite.js
index f4e15648979..f724afb0b31 100644
--- a/lib/helpers/model/castBulkWrite.js
+++ b/lib/helpers/model/castBulkWrite.js
@@ -34,6 +34,9 @@ module.exports = function castBulkWrite(model, op, options) {
     op = op['updateOne'];
     return (callback) => {
       try {
+        if (!op['filter']) throw new Error('Must provide a filter object.');
+        if (!op['update']) throw new Error('Must provide an update object.');
+
         op['filter'] = cast(model.schema, op['filter']);
         op['update'] = castUpdate(model.schema, op['update'], {
           strict: model.schema.options.strict,
@@ -61,6 +64,9 @@ module.exports = function castBulkWrite(model, op, options) {
     op = op['updateMany'];
     return (callback) => {
       try {
+        if (!op['filter']) throw new Error('Must provide a filter object.');
+        if (!op['update']) throw new Error('Must provide an update object.');
+
         op['filter'] = cast(model.schema, op['filter']);
         op['update'] = castUpdate(model.schema, op['update'], {
           strict: model.schema.options.strict,

From a91dc93a3750d024899ac8b3a56a9d2b8f682759 Mon Sep 17 00:00:00 2001
From: Hafez <a.hafez852@gmail.com>
Date: Wed, 13 Nov 2019 16:04:54 +0200
Subject: [PATCH 2/2] Add test for #8331

---
 test/model.test.js | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/test/model.test.js b/test/model.test.js
index a0bf8dc8960..ce2ceddb56e 100644
--- a/test/model.test.js
+++ b/test/model.test.js
@@ -5671,6 +5671,34 @@ describe('Model', function() {
           then(() => Model.findOne()).
           then(doc => assert.equal(doc.nested.name, 'foo'));
       });
+
+      it('throws an error if no update object is provided (gh-8331)', function() {
+        const userSchema = new Schema({ name: { type: String, required: true } });
+        const User = db.model('gh8331', userSchema);
+
+        return co(function*() {
+          const createdUser = yield User.create({ name: 'Hafez' });
+          let threw = false;
+          try {
+            yield User.bulkWrite([{
+              updateOne: {
+                filter: { _id: createdUser._id }
+              }
+            }]);
+          }
+          catch (err) {
+            threw = true;
+            assert.equal(err.message, 'Must provide an update object.');
+          }
+          finally {
+            assert.equal(threw, true);
+
+            const userAfterUpdate = yield User.findOne({ _id: createdUser._id });
+
+            assert.equal(userAfterUpdate.name, 'Hafez', 'Document data is not wiped if no update object is provided.');
+          }
+        });
+      });
     });
 
     it('insertMany with Decimal (gh-5190)', function(done) {