From 6c78829689f8addc26ef0b2ba8fb321e5d86733d Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Sat, 13 Feb 2021 10:40:20 -0500
Subject: [PATCH] fix(model): use schema-level default collation for indexes if
 index doesn't have collation

Fix #9912
---
 lib/model.js               | 4 ++++
 test/model.indexes.test.js | 1 -
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/lib/model.js b/lib/model.js
index 04cb57a31c4..99002b330b3 100644
--- a/lib/model.js
+++ b/lib/model.js
@@ -1650,6 +1650,10 @@ function _ensureIndexes(model, options, callback) {
     if ('background' in options) {
       indexOptions.background = options.background;
     }
+    if (model.schema.options.hasOwnProperty('collation') &&
+        !indexOptions.hasOwnProperty('collation')) {
+      indexOptions.collation = model.schema.options.collation;
+    }
 
     const methodName = useCreateIndex ? 'createIndex' : 'ensureIndex';
     model.collection[methodName](indexFields, indexOptions, utils.tick(function(err, name) {
diff --git a/test/model.indexes.test.js b/test/model.indexes.test.js
index 74e10e97735..50ed7c86125 100644
--- a/test/model.indexes.test.js
+++ b/test/model.indexes.test.js
@@ -569,7 +569,6 @@ describe('model', function() {
         let indexes = yield User.listIndexes();
         assert.equal(indexes.length, 2);
         assert.deepEqual(indexes[1].key, { username: 1 });
-        console.log(indexes);
         assert.ok(indexes[1].collation);
         assert.equal(indexes[1].collation.strength, 2);