From fb0539aa6dca2d1bbf1bc730215c7a8fb7bd13b6 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Sat, 10 Jun 2023 21:32:08 -0400
Subject: [PATCH] fix(query): handle non-string discriminator key values in
 query

Fix #13492
---
 lib/cast.js       | 14 +++++++++++---
 test/cast.test.js | 30 ++++++++++++++++++++++++++++++
 2 files changed, 41 insertions(+), 3 deletions(-)

diff --git a/lib/cast.js b/lib/cast.js
index 1637c2794de..278cc1f00cf 100644
--- a/lib/cast.js
+++ b/lib/cast.js
@@ -118,9 +118,17 @@ module.exports = function cast(schema, obj, options, context) {
             discriminatorKey != null &&
             pathLastHalf !== discriminatorKey) {
             const discriminatorVal = get(obj, pathFirstHalf + '.' + discriminatorKey);
-            if (discriminatorVal != null) {
-              schematype = _schematype.schema.discriminators[discriminatorVal].
-                path(pathLastHalf);
+            const discriminators = _schematype.schema.discriminators;
+            if (typeof discriminatorVal === 'string' && discriminators[discriminatorVal] != null) {
+
+              schematype = discriminators[discriminatorVal].path(pathLastHalf);
+            } else if (discriminatorVal != null &&
+              Object.keys(discriminatorVal).length === 1 &&
+              Array.isArray(discriminatorVal.$in) &&
+              discriminatorVal.$in.length === 1 &&
+              typeof discriminatorVal.$in[0] === 'string' &&
+              discriminators[discriminatorVal.$in[0]] != null) {
+              schematype = discriminators[discriminatorVal.$in[0]].path(pathLastHalf);
             }
           }
         }
diff --git a/test/cast.test.js b/test/cast.test.js
index 51b97518ff3..8557a97eec4 100644
--- a/test/cast.test.js
+++ b/test/cast.test.js
@@ -193,4 +193,34 @@ describe('cast: ', function() {
       name: 'foo'
     });
   });
+
+  it('handles $in with discriminators if $in has exactly 1 element (gh-13492)', function() {
+    const itemStateFooSchema = new Schema({
+      fieldFoo: String
+    });
+
+    const itemSchema = new Schema({
+      state: new Schema(
+        {
+          field: String
+        },
+        {
+          discriminatorKey: 'type'
+        }
+      )
+    });
+
+    itemSchema.path('state').discriminator('FOO', itemStateFooSchema);
+
+    const res = cast(itemSchema, {
+      'state.type': {
+        $in: ['FOO']
+      },
+      'state.fieldFoo': 44
+    });
+    assert.deepStrictEqual(res, {
+      'state.type': { $in: ['FOO'] },
+      'state.fieldFoo': '44'
+    });
+  });
 });