From c371500730310ad3a0362c91f16da2e1f91de8a8 Mon Sep 17 00:00:00 2001
From: Valeri Karpov <val@karpov.io>
Date: Wed, 25 Sep 2019 11:11:16 -0700
Subject: [PATCH] fix(update): cast right hand side of `$pull` as a query
 instead of an update for document arrays

Fix #8166
---
 lib/helpers/query/castUpdate.js | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/lib/helpers/query/castUpdate.js b/lib/helpers/query/castUpdate.js
index 8b289af7af1..37a53b5a7e6 100644
--- a/lib/helpers/query/castUpdate.js
+++ b/lib/helpers/query/castUpdate.js
@@ -4,6 +4,7 @@ const CastError = require('../../error/cast');
 const StrictModeError = require('../../error/strict');
 const ValidationError = require('../../error/validation');
 const castNumber = require('../../cast/number');
+const cast = require('../../cast');
 const getEmbeddedDiscriminatorPath = require('./getEmbeddedDiscriminatorPath');
 const handleImmutable = require('./handleImmutable');
 const utils = require('../../utils');
@@ -139,6 +140,17 @@ function walkUpdatePath(schema, obj, op, options, context, filter, pref) {
     key = keys[i];
     val = obj[key];
 
+    // `$pull` is special because we need to cast the RHS as a query, not as
+    // an update.
+    if (op === '$pull') {
+      schematype = schema._getSchema(prefix + key);
+      if (schematype != null && schematype.schema != null) {
+        obj[key] = cast(schematype.schema, obj[key], options, context);
+        hasKeys = true;
+        continue;
+      }
+    }
+
     if (val && val.constructor.name === 'Object') {
       // watch for embedded doc schemas
       schematype = schema._getSchema(prefix + key);