From 02cd139770c7ad7716c951d8d93c3675164dbd2b Mon Sep 17 00:00:00 2001
From: Andy Butland <abutland73@gmail.com>
Date: Sat, 7 May 2022 12:06:33 +0200
Subject: [PATCH] Fixed issue with null reference when obtaining a lock using a
 detached scope.

---
 .../Scoping/IScopeProvider.cs                 |  4 +++-
 src/Umbraco.Infrastructure/Scoping/Scope.cs   | 20 +++++++++++++++++--
 2 files changed, 21 insertions(+), 3 deletions(-)

diff --git a/src/Umbraco.Infrastructure/Scoping/IScopeProvider.cs b/src/Umbraco.Infrastructure/Scoping/IScopeProvider.cs
index c29ce56a82..a41c64eb08 100644
--- a/src/Umbraco.Infrastructure/Scoping/IScopeProvider.cs
+++ b/src/Umbraco.Infrastructure/Scoping/IScopeProvider.cs
@@ -74,7 +74,9 @@ public interface IScopeProvider : ICoreScopeProvider
     /// <para>A detached scope is not ambient and has no parent.</para>
     /// <para>It is meant to be attached by <see cref="AttachScope"/>.</para>
     /// </remarks>
-    // TODO: This is not actually used apart from unit tests - I'm assuming it's maybe used by Deploy?
+    /// <remarks>
+    /// This is not used by CMS but is used by Umbraco Deploy.
+    /// </remarks>
     IScope CreateDetachedScope(
         IsolationLevel isolationLevel = IsolationLevel.Unspecified,
         RepositoryCacheMode repositoryCacheMode = RepositoryCacheMode.Unspecified,
diff --git a/src/Umbraco.Infrastructure/Scoping/Scope.cs b/src/Umbraco.Infrastructure/Scoping/Scope.cs
index f46ee443f8..190261a808 100644
--- a/src/Umbraco.Infrastructure/Scoping/Scope.cs
+++ b/src/Umbraco.Infrastructure/Scoping/Scope.cs
@@ -130,6 +130,8 @@ namespace Umbraco.Cms.Infrastructure.Scoping
                     _fscope = fileSystems.Shadow();
                 }
 
+                _acquiredLocks = new Queue<IDistributedLock>();
+
                 return;
             }
 
@@ -1204,7 +1206,14 @@ namespace Umbraco.Cms.Infrastructure.Scoping
         /// <param name="lockId">Lock object identifier to lock.</param>
         /// <param name="timeout">TimeSpan specifying the timout period.</param>
         private void ObtainReadLock(int lockId, TimeSpan? timeout)
-            => _acquiredLocks!.Enqueue(_scopeProvider.DistributedLockingMechanismFactory.DistributedLockingMechanism.ReadLock(lockId, timeout));
+        {
+            if (_acquiredLocks == null)
+            {
+                throw new InvalidOperationException($"Cannot obtain a read lock as the {nameof(_acquiredLocks)} queue is null.");
+            }
+
+            _acquiredLocks.Enqueue(_scopeProvider.DistributedLockingMechanismFactory.DistributedLockingMechanism.ReadLock(lockId, timeout));
+        }
 
         /// <summary>
         ///     Obtains a write lock with a custom timeout.
@@ -1212,6 +1221,13 @@ namespace Umbraco.Cms.Infrastructure.Scoping
         /// <param name="lockId">Lock object identifier to lock.</param>
         /// <param name="timeout">TimeSpan specifying the timout period.</param>
         private void ObtainWriteLock(int lockId, TimeSpan? timeout)
-            => _acquiredLocks!.Enqueue(_scopeProvider.DistributedLockingMechanismFactory.DistributedLockingMechanism.WriteLock(lockId, timeout));
+        {
+            if (_acquiredLocks == null)
+            {
+                throw new InvalidOperationException($"Cannot obtain a write lock as the {nameof(_acquiredLocks)} queue is null.");
+            }
+
+            _acquiredLocks.Enqueue(_scopeProvider.DistributedLockingMechanismFactory.DistributedLockingMechanism.WriteLock(lockId, timeout));
+        }
     }
 }