From e2fc83cd33e4dd665e94a4a2a29b228d6abde819 Mon Sep 17 00:00:00 2001
From: Jonas Metzener <jonas.metzener@adfinis.com>
Date: Wed, 2 Apr 2025 16:35:39 +0200
Subject: [PATCH] fix(history): make history aware of potential proxy models

---
 caluma/caluma_core/models.py                  | 58 ++++++++++++++++++-
 .../tests/test_proxy_model_history.py         | 18 ++++++
 2 files changed, 74 insertions(+), 2 deletions(-)
 create mode 100644 caluma/caluma_workflow/tests/test_proxy_model_history.py

diff --git a/caluma/caluma_core/models.py b/caluma/caluma_core/models.py
index 7bbafb2bf..8e99a4914 100644
--- a/caluma/caluma_core/models.py
+++ b/caluma/caluma_core/models.py
@@ -1,6 +1,7 @@
 import uuid_extensions
+from django.apps import apps
 from django.db import models
-from simple_history.models import HistoricalRecords
+from simple_history.models import HistoricalRecords, registered_models
 
 
 def _history_user_getter(historical_instance):
@@ -17,8 +18,61 @@ def _history_user_setter(historical_instance, user):
     historical_instance.history_user_id = user
 
 
+class ProxyAwareHistoricalRecords(HistoricalRecords):
+    """Historical records with shared history for proxy models.
+
+    This is a workaround for https://github.com/jazzband/django-simple-history/issues/544.
+
+    Copied from https://github.com/jazzband/django-simple-history/issues/544#issuecomment-1538615799
+    """
+
+    def _find_base_history(self, opts):
+        base_history = None
+        for parent_class in opts.parents.keys():
+            if hasattr(parent_class, "history"):
+                base_history = parent_class.history.model
+        return base_history
+
+    def create_history_model(self, model, inherited):
+        opts = model._meta
+        if opts.proxy:
+            base_history = self._find_base_history(opts)
+            if base_history:
+                return self.create_proxy_history_model(model, inherited, base_history)
+
+        return super().create_history_model(model, inherited)
+
+    def create_proxy_history_model(self, model, inherited, base_history):
+        opts = model._meta
+        attrs = {
+            "__module__": self.module,
+            "_history_excluded_fields": self.excluded_fields,
+        }
+        app_module = f"{opts.app_label}.models"
+        if inherited:
+            attrs["__module__"] = model.__module__
+        elif model.__module__ != self.module:  # pragma: no cover
+            # registered under different app
+            attrs["__module__"] = self.module
+        elif app_module != self.module:  # pragma: no cover
+            # Abuse an internal API because the app registry is loading.
+            app = apps.app_configs[opts.app_label]
+            models_module = app.name
+            attrs["__module__"] = models_module
+
+        attrs.update(
+            Meta=type("Meta", (), {**self.get_meta_options(model), "proxy": True})
+        )
+        if self.table_name is not None:  # pragma: no cover
+            attrs["Meta"].db_table = self.table_name
+
+        name = self.get_history_model_name(model)
+        registered_models[opts.db_table] = model
+        return type(str(name), (base_history,), attrs)
+
+
 class HistoricalModel(models.Model):
-    history = HistoricalRecords(
+    history = ProxyAwareHistoricalRecords(
         inherit=True,
         history_user_id_field=models.CharField(null=True, max_length=150),
         history_user_setter=_history_user_setter,
diff --git a/caluma/caluma_workflow/tests/test_proxy_model_history.py b/caluma/caluma_workflow/tests/test_proxy_model_history.py
new file mode 100644
index 000000000..c64ad7915
--- /dev/null
+++ b/caluma/caluma_workflow/tests/test_proxy_model_history.py
@@ -0,0 +1,18 @@
+from caluma.caluma_workflow.models import WorkItem
+
+
+def test_proxy_model_history(db, work_item):
+    class ProxyWorkItem(WorkItem):
+        class Meta:
+            proxy = True
+
+    proxy_work_item = ProxyWorkItem.objects.get(pk=work_item.pk)
+
+    assert work_item.history.count() == 1
+    assert proxy_work_item.history.count() == 1
+
+    proxy_work_item.name = "Foo"
+    proxy_work_item.save()
+
+    assert work_item.history.count() == 2
+    assert proxy_work_item.history.count() == 2