From d2d531b5ae54473e91477a7490645cef2cda8be5 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Wed, 3 Mar 2021 20:31:30 -0500
Subject: [PATCH] fix(schema): correctly handle trailing array filters when
 looking up schema paths

Fix #9977
---
 .../schema/cleanPositionalOperators.js        |  4 ++--
 .../schema.cleanPositionalOperators.test.js   | 22 +++++++++++++++++++
 2 files changed, 24 insertions(+), 2 deletions(-)
 create mode 100644 test/helpers/schema.cleanPositionalOperators.test.js

diff --git a/lib/helpers/schema/cleanPositionalOperators.js b/lib/helpers/schema/cleanPositionalOperators.js
index b467be44968..905bb78820b 100644
--- a/lib/helpers/schema/cleanPositionalOperators.js
+++ b/lib/helpers/schema/cleanPositionalOperators.js
@@ -7,6 +7,6 @@
 
 module.exports = function cleanPositionalOperators(path) {
   return path.
-    replace(/\.\$(\[[^\]]*\])?\./g, '.0.').
-    replace(/\.(\[[^\]]*\])?\$$/g, '.0');
+    replace(/\.\$(\[[^\]]*\])?(?=\.)/g, '.0').
+    replace(/\.\$(\[[^\]]*\])?$/g, '.0');
 };
\ No newline at end of file
diff --git a/test/helpers/schema.cleanPositionalOperators.test.js b/test/helpers/schema.cleanPositionalOperators.test.js
new file mode 100644
index 00000000000..e22a7d89015
--- /dev/null
+++ b/test/helpers/schema.cleanPositionalOperators.test.js
@@ -0,0 +1,22 @@
+'use strict';
+
+const assert = require('assert');
+const cleanPositionalOperators = require('../../lib/helpers/schema/cleanPositionalOperators');
+
+describe('cleanPositionalOperators', function() {
+  it('replaces trailing array filter', function() {
+    assert.equal(cleanPositionalOperators('questions.$[q]'), 'questions.0');
+  });
+
+  it('replaces trailing $', function() {
+    assert.equal(cleanPositionalOperators('questions.$'), 'questions.0');
+  });
+
+  it('replaces interior array filters', function() {
+    assert.equal(cleanPositionalOperators('questions.$[q].$[r].test'), 'questions.0.0.test');
+  });
+
+  it('replaces interior elemMatch', function() {
+    assert.equal(cleanPositionalOperators('questions.$.$.test'), 'questions.0.0.test');
+  });
+});
\ No newline at end of file