Handle missing request (#1256)

* Handle if `request` doesn't exist on the context in middleware

The change in #1188
removed a check for if the request context had a "request" entry in it before
trying to delete the request data.

This has a side effect of breaking tests in order projects in very specific
circumstances, where multiple requests pass through the middleware,
concurrently, inside the same thread, as it means the middleware then may try
to remove the request key on a context where it already has been removed.

This shouldn't have any impact in real life scenarios.

* Add changelog entry

* Improvement of changelog for #1256

Also added a missing reference to the previously merged PR.

---------

Co-authored-by: Anders <[email protected]>

Author: Tenzer

AUTHORS.rst

@@ -64,6 +64,7 @@ Authors
 - Jake Howard (`RealOrangeOne <https://github.com/realorangeone>`_)
 - James Muranga (`jamesmura <https://github.com/jamesmura>`_)
 - James Pulec
+- Jeppe Fihl-Pearson (`Tenzer <https://github.com/Tenzer>`_)
 - Jesse Shapiro
 - Jihoon Baek (`jihoon796 <https://github.com/jihoon796>`_)
 - Jim Gomez

CHANGES.rst

@@ -4,7 +4,9 @@ Changes
 Unreleased
 ----------
 
-- Allow ``HistoricalRecords.m2m_fields`` as str
+- Allow ``HistoricalRecords.m2m_fields`` as str (gh-1243)
+- Fixed ``HistoryRequestMiddleware`` deleting non-existent
+  ``HistoricalRecords.context.request`` in very specific circumstances (gh-1256)
 
 3.4.0 (2023-08-18)
 ------------------

simple_history/middleware.py

@@ -13,7 +13,10 @@ def _context_manager(request):
     try:
         yield None
     finally:
-        del HistoricalRecords.context.request
+        try:
+            del HistoricalRecords.context.request
+        except AttributeError:
+            pass
 
 
 @sync_and_async_middleware