feat: m2m_fields accepts field names (#1243)

CHANGES.rst

@@ -4,6 +4,7 @@ Changes
 Unreleased
 ----------
 
+- Allow ``HistoricalRecords.m2m_fields`` as str
 
 3.4.0 (2023-08-18)
 ------------------

docs/historical_model.rst

@@ -469,9 +469,12 @@ If you want to track many to many relationships, you need to define them explici
 This will create a historical intermediate model that tracks each relational change
 between `Poll` and `Category`.
 
-You may also define these fields in a model attribute (by default on `_history_m2m_fields`).
-This is mainly used for inherited models. You can override the attribute name by setting
-your own `m2m_fields_model_field_name` argument on the `HistoricalRecord` instance.
+You may use either the name of the field or the field instance itself.
+
+You may also define these fields in a class attribute (by default on `_history_m2m_fields`).
+This is mainly used by inherited models not declaring their own `HistoricalRecord`.
+You can override the attribute name by setting your own `m2m_fields_model_field_name`
+argument on the `HistoricalRecord` instance.
 
 You will see the many to many changes when diffing between two historical records:
 

simple_history/models.py

@@ -768,7 +768,10 @@ def get_m2m_fields_from_model(self, model):
             m2m_fields.update(getattr(model, self.m2m_fields_model_field_name))
         except AttributeError:
             pass
-        return [getattr(model, field.name).field for field in m2m_fields]
+        field_names = [
+            field if isinstance(field, str) else field.name for field in m2m_fields
+        ]
+        return [getattr(model, field_name).field for field_name in field_names]
 
 
 def transform_field(field):

simple_history/tests/models.py

@@ -190,7 +190,7 @@ class Meta:
 
 class PollChildBookWithManyToMany(PollParentWithManyToMany):
     books = models.ManyToManyField("Book", related_name="books_poll_child")
-    _history_m2m_fields = [books]
+    _history_m2m_fields = ["books"]
 
 
 class PollChildRestaurantWithManyToMany(PollParentWithManyToMany):