Make historical records' m2m fields type-compatible with non-historical

Fixes #1186

Author: mjsir911

simple_history/manager.py

@@ -127,6 +127,35 @@ def __get__(self, instance, owner):
         return HistoryManager.from_queryset(HistoricalQuerySet)(self.model, instance)
 
 
+class HistoryManyToManyDescriptor:
+    def __init__(self, model, rel):
+        self.rel = rel
+        self.model = model
+
+    def __get__(self, instance, owner):
+        return HistoryManyRelatedManager.from_queryset(QuerySet)(
+            self.model, self.rel, instance
+        )
+
+
+class HistoryManyRelatedManager(models.Manager):
+    def __init__(self, through, rel, instance=None):
+        super().__init__()
+        self.model = rel.model
+        self.through = through
+        self.instance = instance
+        self._m2m_through_field_name = rel.field.m2m_reverse_field_name()
+
+    def get_queryset(self):
+        qs = super().get_queryset()
+        through_qs = HistoryManager.from_queryset(HistoricalQuerySet)(
+            self.through, self.instance
+        )
+        return qs.filter(
+            pk__in=through_qs.all().values_list(self._m2m_through_field_name, flat=True)
+        )
+
+
 class HistoryManager(models.Manager):
     def __init__(self, model, instance=None):
         super().__init__()

simple_history/models.py

@@ -31,7 +31,11 @@
 from simple_history import utils
 
 from . import exceptions
-from .manager import SIMPLE_HISTORY_REVERSE_ATTR_NAME, HistoryDescriptor
+from .manager import (
+    SIMPLE_HISTORY_REVERSE_ATTR_NAME,
+    HistoryDescriptor,
+    HistoryManyToManyDescriptor,
+)
 from .signals import (
     post_create_historical_m2m_records,
     post_create_historical_record,
@@ -227,7 +231,7 @@ def finalize(self, sender, **kwargs):
 
             setattr(module, m2m_model.__name__, m2m_model)
 
-            m2m_descriptor = HistoryDescriptor(m2m_model)
+            m2m_descriptor = HistoryManyToManyDescriptor(m2m_model, field.remote_field)
             setattr(history_model, field.name, m2m_descriptor)
 
     def get_history_model_name(self, model):