Added tracked_fields attr to historical models

This attribute can be useful for future code and for users, as there is currently no easy way (known to me) to list
the fields of a model that are tracked (i.e. not excluded) by a history model.

The attribute will also be used in an upcoming bugfix, which was the main motivation for adding this.

Author: ddabble

CHANGES.rst

@@ -9,6 +9,7 @@ Unreleased
 - Started using ``exists`` query instead of ``count`` in ``populate_history`` command (gh-982)
 - Add basic support for many-to-many fields (gh-399)
 - Added support for Django 4.1 (gh-1021)
+- Added ``tracked_fields`` attribute to historical models (gh-1038)
 
 3.1.1 (2022-04-23)
 ------------------

simple_history/manager.py

@@ -155,11 +155,8 @@ def most_recent(self):
                 )
             )
         tmp = []
-        excluded_fields = getattr(self.model, "_history_excluded_fields", [])
 
-        for field in self.instance._meta.fields:
-            if field.name in excluded_fields:
-                continue
+        for field in self.model.tracked_fields:
             if isinstance(field, models.ForeignKey):
                 tmp.append(field.name + "_id")
             else:
@@ -263,8 +260,7 @@ def bulk_history_create(
                 history_type=history_type,
                 **{
                     field.attname: getattr(instance, field.attname)
-                    for field in instance._meta.fields
-                    if field.name not in self.model._history_excluded_fields
+                    for field in self.model.tracked_fields
                 },
             )
             if hasattr(self.model, "history_relation"):

simple_history/models.py

@@ -274,6 +274,7 @@ def create_history_model(self, model, inherited):
             "__module__": self.module,
             "_history_excluded_fields": self.excluded_fields,
             "_history_m2m_fields": self.get_m2m_fields_from_model(model),
+            "tracked_fields": self.fields_included(model),
         }
 
         app_module = "%s.models" % model._meta.app_label

simple_history/tests/tests/test_models.py

@@ -77,6 +77,7 @@
     InheritedRestaurant,
     Library,
     ManyToManyModelOther,
+    ModelWithCustomAttrOneToOneField,
     ModelWithExcludedManyToMany,
     ModelWithFkToModelWithHistoryUsingBaseModelDb,
     ModelWithHistoryInDifferentDb,
@@ -93,6 +94,7 @@
     PollChildBookWithManyToMany,
     PollChildRestaurantWithManyToMany,
     PollInfo,
+    PollWithAlternativeManager,
     PollWithExcludedFieldsWithDefaults,
     PollWithExcludedFKField,
     PollWithExcludeFields,
@@ -905,6 +907,51 @@ def create_history_model(model, inherited):
         records.module = model.__module__
         return records.create_history_model(model, inherited)
 
+    def test_create_history_model_has_expected_tracked_files_attr(self):
+        def assert_tracked_fields_equal(model, expected_field_names):
+            from .. import models
+
+            history_model = getattr(
+                models, f"Historical{model.__name__}"
+            )
+            self.assertListEqual(
+                [field.name for field in history_model.tracked_fields],
+                expected_field_names,
+            )
+
+        assert_tracked_fields_equal(
+            Poll,
+            ["id", "question", "pub_date"],
+        )
+        assert_tracked_fields_equal(
+            PollWithNonEditableField,
+            ["id", "question", "pub_date", "modified"],
+        )
+        assert_tracked_fields_equal(
+            PollWithExcludeFields,
+            ["id", "question", "place"],
+        )
+        assert_tracked_fields_equal(
+            PollWithExcludedFieldsWithDefaults,
+            ["id", "question"],
+        )
+        assert_tracked_fields_equal(
+            PollWithExcludedFKField,
+            ["id", "question", "pub_date"],
+        )
+        assert_tracked_fields_equal(
+            PollWithAlternativeManager,
+            ["id", "question", "pub_date"],
+        )
+        assert_tracked_fields_equal(
+            PollWithHistoricalIPAddress,
+            ["id", "question", "pub_date"],
+        )
+        assert_tracked_fields_equal(
+            ModelWithCustomAttrOneToOneField,
+            ["id", "poll"],
+        )
+
     def test_create_history_model_with_one_to_one_field_to_integer_field(self):
         try:
             self.create_history_model(AdminProfile, False)