From d48cfa111323f5b73233f4cd00b7eaa70a7a0006 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Wed, 26 Aug 2020 21:19:26 -0400
Subject: [PATCH] fix(queryhelpers): avoid path collision error when projecting
 in discriminator key with `.$`

Re: #9361
---
 lib/queryhelpers.js              |  2 +-
 test/model.discriminator.test.js | 18 +++++++++++-------
 2 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/lib/queryhelpers.js b/lib/queryhelpers.js
index 53a6f613613..d0e93b65b42 100644
--- a/lib/queryhelpers.js
+++ b/lib/queryhelpers.js
@@ -261,7 +261,7 @@ exports.applyPaths = function applyPaths(fields, schema) {
       let cur = '';
       for (let i = 0; i < pieces.length; ++i) {
         cur += (cur.length === 0 ? '' : '.') + pieces[i];
-        const projection = get(fields, cur, false);
+        const projection = get(fields, cur, false) || get(fields, cur + '.$', false);
         if (projection && typeof projection !== 'object') {
           return;
         }
diff --git a/test/model.discriminator.test.js b/test/model.discriminator.test.js
index cc1838aa2cc..0b50a0b6b07 100644
--- a/test/model.discriminator.test.js
+++ b/test/model.discriminator.test.js
@@ -762,31 +762,35 @@ describe('model', function() {
 
       it('with $meta projection (gh-5859)', function() {
         const eventSchema = new Schema({ eventField: String }, { id: false });
+        eventSchema.index({ eventField: 'text' });
         const Event = db.model('Test', eventSchema);
 
         const trackSchema = new Schema({ trackField: String });
         const Track = Event.discriminator('Track', trackSchema);
 
         const trackedItem = new Track({
-          trackField: 'trackField',
-          eventField: 'eventField'
+          trackField: 'track',
+          eventField: 'event'
         });
 
         return trackedItem.save().
+          then(() => Event.init()).
           then(function() {
-            return Event.find({}).select({ score: { $meta: 'textScore' } });
+            return Event.find({ $text: { $search: 'event' } }).
+              select({ score: { $meta: 'textScore' } });
           }).
           then(function(docs) {
             assert.equal(docs.length, 1);
-            assert.equal(docs[0].trackField, 'trackField');
+            assert.equal(docs[0].trackField, 'track');
           }).
           then(function() {
-            return Track.find({}).select({ score: { $meta: 'textScore' } });
+            return Track.find({ $text: { $search: 'event' } }).
+              select({ score: { $meta: 'textScore' } });
           }).
           then(function(docs) {
             assert.equal(docs.length, 1);
-            assert.equal(docs[0].trackField, 'trackField');
-            assert.equal(docs[0].eventField, 'eventField');
+            assert.equal(docs[0].trackField, 'track');
+            assert.equal(docs[0].eventField, 'event');
           });
       });