fix: avoid applying map property getters when saving

lib/utils.js

@@ -630,9 +630,23 @@ function _populateObj(obj) {
  */
 
 exports.getValue = function(path, obj, map) {
-  return mpath.get(path, obj, '_doc', map);
+  return mpath.get(path, obj, getValueLookup, map);
 };
 
+/*!
+ * ignore
+ */
+
+const mapGetterOptions = Object.freeze({ getters: false });
+
+function getValueLookup(obj, part) {
+  const _from = obj && obj._doc ? obj._doc : obj;
+  obj = _from instanceof Map ?
+    _from.get(part, mapGetterOptions) :
+    _from[part];
+  return obj;
+}
+
 /**
  * Sets the value of `obj` at the given `path`.
  *

test/schema.uuid.test.js

@@ -172,6 +172,37 @@ describe('SchemaUUID', function() {
     assert.equal(_id, uuid.toString());
   });
 
+  it('avoids converting maps of uuids to strings (gh-13657)', async function() {
+    const schema = new mongoose.Schema(
+      {
+        doc_map: {
+          type: mongoose.Schema.Types.Map,
+          of: mongoose.Schema.Types.UUID
+        }
+      }
+    );
+    db.deleteModel(/Test/);
+    const Test = db.model('Test', schema);
+    await Test.deleteMany({});
+
+    const user = new Test({
+      doc_map: new Map([
+        ['role_1', new mongoose.Types.UUID()],
+        ['role_2', new mongoose.Types.UUID()]
+      ])
+    });
+
+    await user.save();
+
+    user.doc_map.set('role_1', new mongoose.Types.UUID());
+    await user.save();
+
+    const exists = await Test.findOne({ 'doc_map.role_1': { $type: 'binData' } });
+    assert.ok(exists);
+
+    assert.equal(typeof user.get('doc_map.role_1'), 'string');
+  });
+
   // the following are TODOs based on SchemaUUID.prototype.$conditionalHandlers which are not tested yet
   it('should work with $bits* operators');
   it('should work with $all operator');