fix: report default paths in VersionError message because they can can cause VersionError

lib/model.js

@@ -460,8 +460,8 @@ Model.prototype.$__handleSave = function(options, callback) {
     return;
   }
 
-  // store the modified paths before the document is reset
-  this.$__.modifiedPaths = this.modifiedPaths();
+  // store the modified paths before the document is reset in case we need to generate version error.
+  this.$__.modifiedPaths = this.modifiedPaths().concat(Object.keys(this.$__.activePaths.getStatePaths('default')));
   this.$__reset();
 
   _setIsNew(this, false);
@@ -562,13 +562,13 @@ Model.prototype.$__save = function(options, callback) {
  * ignore
  */
 
-function generateVersionError(doc, modifiedPaths) {
+function generateVersionError(doc, modifiedPaths, defaultPaths) {
   const key = doc.$__schema.options.versionKey;
   if (!key) {
     return null;
   }
   const version = doc.$__getValue(key) || 0;
-  return new VersionError(doc, version, modifiedPaths);
+  return new VersionError(doc, version, modifiedPaths.concat(defaultPaths));
 }
 
 /**
@@ -626,7 +626,11 @@ Model.prototype.save = async function save(options) {
   if (this.$__.timestamps != null) {
     options.timestamps = this.$__.timestamps;
   }
-  this.$__.$versionError = generateVersionError(this, this.modifiedPaths());
+  this.$__.$versionError = generateVersionError(
+    this,
+    this.modifiedPaths(),
+    Object.keys(this.$__.activePaths.getStatePaths('default'))
+  );
 
   if (parallelSave) {
     this.$__handleReject(parallelSave);

test/document.test.js

@@ -14469,6 +14469,33 @@ describe('document', function() {
     assert.strictEqual(strValidateCalls, 1);
 
   });
+
+  it('triggers VersionError when using push() to an array', async function() {
+    const schema = new Schema({ texts: [{ text: String, _id: false }], test: String });
+    const Test = db.model('Test', schema);
+
+    const doc = new Test({ texts: [{ text: 'test' }], test: 'Test' });
+    await doc.save();
+    await Test.collection.updateOne({ _id: doc._id }, { $unset: { texts: 1 } });
+
+    // Get two instances of the same document to create a version conflict
+    const doc1 = await Test.findById(doc._id);
+    const doc2 = await Test.findById(doc._id);
+
+    // Modify and save the first instance
+    doc1.texts.push({ text: 'name1' });
+    await doc1.save();
+
+    // Try to modify and save the second instance
+    // This should cause a VersionError because `texts` gets a default value of `[]`.
+    doc2.test = null;
+
+    // Should throw VersionError because doc1 was saved with a new version number
+    const err = await doc2.save().then(() => null, err => err);
+    assert.ok(err);
+    assert.strictEqual(err.name, 'VersionError');
+    assert.ok(err.message.includes('texts'));
+  });
 });
 
 describe('Check if instance function that is supplied in schema option is available', function() {