fix(document): allow setting keys with dots in mixed paths underneath nested paths

docs/connections.md

@@ -6,9 +6,9 @@ You can connect to MongoDB with the `mongoose.connect()` method.
 mongoose.connect('mongodb://127.0.0.1:27017/myapp');
 ```
 
-This is the minimum needed to connect the `myapp` database running locally
-on the default port (27017). If connecting fails on your machine, try using
-`127.0.0.1` instead of `localhost`.
+This is the minimum needed to connect the `myapp` database running locally on the default port (27017).
+For local MongoDB databases, we recommend using `127.0.0.1` instead of `localhost`.
+That is because Node.js 18 and up prefer IPv6 addresses, which means, on many machines, Node.js will resolve `localhost` to the IPv6 address `::1` and Mongoose will be unable to connect, unless the mongodb instance is running with ipv6 enabled.
 
 You can also specify several more parameters in the `uri`:
 

docs/faq.md

@@ -12,6 +12,19 @@ hr {
 }
 </style>
 
+<hr id="localhost-ipv6" />
+
+<a class="anchor" href="#localhost-ipv6">**Q**</a>. I get an error `connect ECONNREFUSED ::1:27017` when connecting to `localhost`. Why?
+
+The easy solution is to replace `localhost` with `127.0.0.1`.
+
+The reason why this error happens is that Node.js 18 and up prefer IPv6 addresses over IPv4 by default.
+And, most Linux and OSX machines have a `::1     localhost` entry in `/etc/hosts` by default.
+That means that Node.js 18 will assume that `localhost` means the IPv6 `::1` address.
+And MongoDB doesn't accept IPv6 connections by default.
+
+You can also fix this error by [enabling IPv6 support on your MongoDB server](https://www.mongodb.com/docs/manual/core/security-mongodb-configuration/).
+
 <hr id="operation-buffering-timed-out" />
 
 <a class="anchor" href="#operation-buffering-timed-out">**Q**</a>. Operation `...` timed out after 10000 ms. What gives?

lib/document.js

@@ -22,7 +22,6 @@ const clone = require('./helpers/clone');
 const compile = require('./helpers/document/compile').compile;
 const defineKey = require('./helpers/document/compile').defineKey;
 const flatten = require('./helpers/common').flatten;
-const flattenObjectWithDottedPaths = require('./helpers/path/flattenObjectWithDottedPaths');
 const get = require('./helpers/get');
 const getEmbeddedDiscriminatorPath = require('./helpers/document/getEmbeddedDiscriminatorPath');
 const getKeysInSchemaOrder = require('./helpers/schema/getKeysInSchemaOrder');
@@ -473,8 +472,6 @@ function $applyDefaultsToNested(val, path, doc) {
     return;
   }
 
-  flattenObjectWithDottedPaths(val);
-
   const paths = Object.keys(doc.$__schema.paths);
   const plen = paths.length;
 

test/document.test.js

@@ -12212,6 +12212,27 @@ describe('document', function() {
     const fromDb = await Test.findById(x._id).lean();
     assert.equal(fromDb.c.x.y, 1);
   });
+
+  it('should allow storing keys with dots in name in mixed under nested (gh-13530)', async function() {
+    const TestModelSchema = new mongoose.Schema({
+      metadata:
+        {
+          labels: mongoose.Schema.Types.Mixed
+        }
+    });
+    const TestModel = db.model('Test', TestModelSchema);
+    const { _id } = await TestModel.create({
+      metadata: {
+        labels: { 'my.label.com': 'true' }
+      }
+    });
+    const doc = await TestModel.findById(_id).lean();
+    assert.deepStrictEqual(doc.metadata, {
+      labels: {
+        'my.label.com': 'true'
+      }
+    });
+  });
 });
 
 describe('Check if instance function that is supplied in schema option is availabe', function() {