From e3c8947883b55fdccf55d245e4859adc96de0d95 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Laura=20Kl=C3=BCnder?= <laura@codingcatgirl.de>
Date: Tue, 13 Jun 2017 18:52:16 +0200
Subject: [PATCH] do creepy metaclass stuff in wrappers.py

---
 src/c3nav/editor/api.py      |  1 +
 src/c3nav/editor/models.py   |  2 +-
 src/c3nav/editor/wrappers.py | 48 +++++++++++++++++++++++++-----------
 3 files changed, 35 insertions(+), 16 deletions(-)

diff --git a/src/c3nav/editor/api.py b/src/c3nav/editor/api.py
index fcd46cf4..6d3807b7 100644
--- a/src/c3nav/editor/api.py
+++ b/src/c3nav/editor/api.py
@@ -76,6 +76,7 @@ class EditorViewSet(ViewSet):
             levels = Level.objects.filter(pk__in=levels).prefetch_related('buildings', 'spaces', 'doors',
                                                                           'spaces__groups', 'spaces__holes',
                                                                           'spaces__columns')
+
             levels = {s.pk: s for s in levels}
 
             level = levels[level.pk]
diff --git a/src/c3nav/editor/models.py b/src/c3nav/editor/models.py
index 0fa6ef3d..a0d588ef 100644
--- a/src/c3nav/editor/models.py
+++ b/src/c3nav/editor/models.py
@@ -120,7 +120,7 @@ class ChangeSet(models.Model):
         if isinstance(obj, type) and issubclass(obj, models.Model):
             return ModelWrapper(self, obj, author)
         if isinstance(obj, models.Model):
-            return ModelInstanceWrapper(self, obj, author)
+            return ModelWrapper(self, type(obj), author).create_wrapped_model_class()(self, obj, author)
         raise ValueError
 
     def _new_change(self, author, **kwargs):
diff --git a/src/c3nav/editor/wrappers.py b/src/c3nav/editor/wrappers.py
index 1d9ad33f..e4f69aa5 100644
--- a/src/c3nav/editor/wrappers.py
+++ b/src/c3nav/editor/wrappers.py
@@ -1,7 +1,5 @@
-from collections import deque
-
 from django.db import models
-from django.db.models import Manager, Prefetch
+from django.db.models import Manager
 from django.db.models.fields.related_descriptors import ForwardManyToOneDescriptor
 
 
@@ -15,12 +13,15 @@ class BaseWrapper:
         self._obj = obj
 
     def _wrap_model(self, model):
+        assert issubclass(model, models.Model)
         return ModelWrapper(self._changeset, model, self._author)
 
     def _wrap_instance(self, instance):
-        return ModelInstanceWrapper(self._changeset, instance, self._author)
+        assert isinstance(instance, models.Model)
+        return self._wrap_model(type(instance)).create_wrapped_model_class()(self._changeset, instance, self._author)
 
     def _wrap_manager(self, manager):
+        assert isinstance(manager, Manager)
         if hasattr(manager, 'through'):
             return ManyRelatedManagerWrapper(self._changeset, manager, self._author)
         return ManagerWrapper(self._changeset, manager, self._author)
@@ -53,19 +54,39 @@ class BaseWrapper:
 
 
 class ModelWrapper(BaseWrapper):
-    _allowed_callables = ('EditorForm', )
+    _allowed_callables = ('EditorForm',)
 
     def __eq__(self, other):
         if type(other) == ModelWrapper:
             return self._obj is other._obj
         return self._obj is other
 
+    def create_wrapped_model_class(self):
+        return self.create_metaclass()(self._obj.__name__ + 'InstanceWrapper', (ModelInstanceWrapper,), {})
+
     def __call__(self, **kwargs):
         instance = self._wrap_instance(self._obj())
         for name, value in kwargs.items():
             setattr(instance, name, value)
         return instance
 
+    def create_metaclass(self):
+        parent = self
+
+        class ModelInstanceWrapperMeta(type):
+            def __getattr__(self, name):
+                return getattr(parent, name)
+
+            def __setattr__(self, name, value):
+                setattr(parent, name, value)
+
+            def __delattr__(self, name):
+                delattr(parent, name)
+
+        ModelInstanceWrapperMeta.__name__ = self._obj.__name__+'InstanceWrapperMeta'
+
+        return ModelInstanceWrapperMeta
+
 
 class ModelInstanceWrapper(BaseWrapper):
     _allowed_callables = ('full_clean', 'validate_unique')
@@ -108,6 +129,8 @@ class ModelInstanceWrapper(BaseWrapper):
             return super().__setattr__(name, value)
         class_value = getattr(type(self._obj), name, None)
         if isinstance(class_value, ForwardManyToOneDescriptor) and value is not None:
+            if isinstance(value, models.Model):
+                value = self._wrap_instance(value)
             if not isinstance(value, ModelInstanceWrapper):
                 raise ValueError('value has to be None or ModelInstanceWrapper')
             setattr(self._obj, name, value._obj)
@@ -188,16 +211,7 @@ class BaseQueryWrapper(BaseWrapper):
         return self._wrap_queryset(self._obj.select_related(*args, **kwargs))
 
     def prefetch_related(self, *lookups):
-        new_lookups = deque()
-        for lookup in lookups:
-            if not isinstance(lookup, str):
-                new_lookups.append(lookup)
-                continue
-            model = self._obj.model
-            for name in lookup.split('__'):
-                model = model._meta.get_field(name).related_model
-            new_lookups.append(Prefetch(lookup, self._wrap_model(model).objects.all()))
-        return self._wrap_queryset(self._obj.prefetch_related(*new_lookups))
+        return self._wrap_queryset(self._obj.prefetch_related(*lookups))
 
     def get(self, **kwargs):
         return self._wrap_instance(self._obj.get(**kwargs))
@@ -274,6 +288,10 @@ class ManyRelatedManagerWrapper(ManagerWrapper):
             pk = (obj.pk if isinstance(obj, self._obj.model) else obj)
             self._changeset.add_m2m_remove(self._obj.instance, name=self.prefetch_cache_name, value=pk, author=author)
 
+    def get_prefetch_queryset(self, instances, queryset=None):
+        value = self._obj.get_prefetch_queryset(instances, queryset=queryset)
+        return value
+
 
 class QuerySetWrapper(BaseQueryWrapper):
     @property