Merge pull request #13427 from Automattic/IslandRhythms/gh-13379

fix: avoid setting null property when updating doc

lib/helpers/update/applyTimestampsToUpdate.js

@@ -44,11 +44,12 @@ function applyTimestampsToUpdate(now, createdAt, updatedAt, currentUpdate, optio
 
   if (Array.isArray(updates)) {
     // Update with aggregation pipeline
+    if (updatedAt == null) {
+      return updates;
+    }
     updates.push({ $set: { [updatedAt]: now } });
-
     return updates;
   }
-
   updates.$set = updates.$set || {};
   if (!skipUpdatedAt && updatedAt &&
       (!currentUpdate.$currentDate || !currentUpdate.$currentDate[updatedAt])) {

test/timestamps.test.js

@@ -1009,6 +1009,39 @@ describe('timestamps', function() {
       assert.deepStrictEqual(keys, ['location', '_id', 'createdAt', 'updatedAt']);
     }
   });
+  it('should avoid setting null update when updating document with timestamps gh-13379', async function() {
+
+    const subWithTimestampSchema = new Schema({
+      subName: {
+        type: String,
+        default: 'anonymous',
+        required: true
+      }
+    });
+
+    subWithTimestampSchema.set('timestamps', true);
+
+    const testSchema = new Schema({
+      name: String,
+      sub: { type: subWithTimestampSchema }
+    });
+
+    const Test = db.model('gh13379', testSchema);
+
+    const doc = new Test({
+      name: 'Test Testerson',
+      sub: { subName: 'John' }
+    });
+    await doc.save();
+    await Test.updateMany({}, [{ $set: { updateCounter: 1 } }]);
+    // oddly enough, the null property is not accessible. Doing check.null doesn't return anything even though
+    // if you were to console.log() the output of a findOne you would be able to see it. This is the workaround.
+    const test = await Test.countDocuments({ null: { $exists: true } });
+    assert.equal(test, 0);
+    // now we need to make sure that the solution didn't prevent the updateCounter addition
+    const check = await Test.findOne();
+    assert(check.toString().includes('updateCounter: 1'));
+  });
 });
 
 async function delay(ms) {