Merge pull request #67 from hstanev/master

Check if migrations are allowed for the model before applying it
jazzband · Nov 26, 2015 · a7796a9 · a7796a9
2 parents 2f7a2c2 + 07593fb
commit a7796a9
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Showing 2 changed files with 44 additions and 34 deletions.
diff --git a/sortedm2m/compat.py b/sortedm2m/compat.py
@@ -49,3 +49,10 @@ def get_apps_from_state(migration_state):
         return migration_state.render()
     else:
         return migration_state.apps
+
+
+def allow_migrate_model(self, connection_alias, model):
+    if django.VERSION < (1, 8):
+        return self.allowed_to_migrate(connection_alias, model)
+    else:
+        return self.allow_migrate_model(connection_alias, model)
diff --git a/sortedm2m/operations.py b/sortedm2m/operations.py
@@ -4,6 +4,7 @@
 from sortedm2m.fields import SORT_VALUE_FIELD_NAME
 from .compat import get_field
 from .compat import get_apps_from_state
+from .compat import allow_migrate_model
 
 
 class AlterSortedManyToManyField(AlterField):
@@ -13,27 +14,28 @@ class AlterSortedManyToManyField(AlterField):
     def database_forwards(self, app_label, schema_editor, from_state, to_state):
         to_apps = get_apps_from_state(to_state)
         to_model = to_apps.get_model(app_label, self.model_name)
-        to_field = get_field(to_model, self.name)
+        if allow_migrate_model(self, schema_editor.connection.alias, to_model):
+            to_field = get_field(to_model, self.name)
 
-        from_apps = get_apps_from_state(from_state)
-        from_model = from_apps.get_model(app_label, self.model_name)
-        from_field = get_field(from_model, self.name)
+            from_apps = get_apps_from_state(from_state)
+            from_model = from_apps.get_model(app_label, self.model_name)
+            from_field = get_field(from_model, self.name)
 
-        to_m2m_model = to_field.rel.through
-        from_m2m_model = from_field.rel.through
+            to_m2m_model = to_field.rel.through
+            from_m2m_model = from_field.rel.through
 
-        # M2M -> SortedM2M
-        if getattr(to_field, 'sorted', False):
-            self.add_sort_value_field(schema_editor, to_m2m_model)
-        # SortedM2M -> M2M
-        elif getattr(from_field, 'sorted', False):
-            self.remove_sort_value_field(schema_editor, from_m2m_model)
-        else:
-            raise TypeError(
-                '{operation} should only be used when changing a '
-                'SortedManyToManyField into a ManyToManyField or a '
-                'ManyToManyField into a SortedManyToManyField.'
-                .format(operation=self.__class__.__name__))
+            # M2M -> SortedM2M
+            if getattr(to_field, 'sorted', False):
+                self.add_sort_value_field(schema_editor, to_m2m_model)
+            # SortedM2M -> M2M
+            elif getattr(from_field, 'sorted', False):
+                self.remove_sort_value_field(schema_editor, from_m2m_model)
+            else:
+                raise TypeError(
+                    '{operation} should only be used when changing a '
+                    'SortedManyToManyField into a ManyToManyField or a '
+                    'ManyToManyField into a SortedManyToManyField.'
+                    .format(operation=self.__class__.__name__))
 
     def database_backwards(self, app_label, schema_editor, from_state, to_state):
         from_apps = get_apps_from_state(from_state)
@@ -42,25 +44,26 @@ def database_backwards(self, app_label, schema_editor, from_state, to_state):
 
         to_apps = get_apps_from_state(to_state)
         to_model = to_apps.get_model(app_label, self.model_name)
-        to_field = get_field(to_model, self.name)
 
-        from_m2m_model = from_field.rel.through
-        to_m2m_model = to_field.rel.through
+        if allow_migrate_model(self, schema_editor.connection.alias, to_model):
+            to_field = get_field(to_model, self.name)
+            from_m2m_model = from_field.rel.through
+            to_m2m_model = to_field.rel.through
 
-        # The `to_state` is the OLDER state.
+            # The `to_state` is the OLDER state.
 
-        # M2M -> SortedM2M (backwards)
-        if getattr(to_field, 'sorted', False):
-            self.add_sort_value_field(schema_editor, to_m2m_model)
-        # SortedM2M -> M2M (backwards)
-        elif getattr(from_field, 'sorted', False):
-            self.remove_sort_value_field(schema_editor, from_m2m_model)
-        else:
-            raise TypeError(
-                '{operation} should only be used when changing a '
-                'SortedManyToManyField into a ManyToManyField or a '
-                'ManyToManyField into a SortedManyToManyField.'
-                .format(operation=self.__class__.__name__))
+            # M2M -> SortedM2M (backwards)
+            if getattr(to_field, 'sorted', False):
+                self.add_sort_value_field(schema_editor, to_m2m_model)
+            # SortedM2M -> M2M (backwards)
+            elif getattr(from_field, 'sorted', False):
+                self.remove_sort_value_field(schema_editor, from_m2m_model)
+            else:
+                raise TypeError(
+                    '{operation} should only be used when changing a '
+                    'SortedManyToManyField into a ManyToManyField or a '
+                    'ManyToManyField into a SortedManyToManyField.'
+                    .format(operation=self.__class__.__name__))
 
     def add_sort_value_field(self, schema_editor, model):
         field = self.make_sort_by_field(model)