Fix collections names no longer unique when moved around

We were not checking for uniqueness after moving. And in some cases the new
siblings of our collection may have conflicting names.

source/blender/blenkernel/intern/collection.c

@@ -314,6 +314,15 @@ void BKE_collection_rename(const Scene *scene, SceneCollection *sc, const char *
 	collection_rename(&scene->id, sc, name);
 }
 
+/**
+ * Make sure the collection name is still unique within its siblings.
+ */
+static void collection_name_check(const ID *owner_id, SceneCollection *sc)
+{
+	/* It's a bit of a hack, we simply try to make sure the collection name is valid. */
+	collection_rename(owner_id, sc, sc->name);
+}
+
 /**
  * Free (or release) any data used by the master collection (does not free the master collection itself).
  * Used only to clear the entire scene or group data since it's not doing re-syncing of the LayerCollection tree
@@ -589,6 +598,9 @@ bool BKE_collection_move_above(const ID *owner_id, SceneCollection *sc_dst, Scen
 	BKE_layer_collection_resync(owner_id, sc_src_parent);
 	BKE_layer_collection_resync(owner_id, sc_dst_parent);
 
+	/* Keep names unique. */
+	collection_name_check(owner_id, sc_src);
+
 	return true;
 }
 
@@ -628,6 +640,9 @@ bool BKE_collection_move_below(const ID *owner_id, SceneCollection *sc_dst, Scen
 	BKE_layer_collection_resync(owner_id, sc_src_parent);
 	BKE_layer_collection_resync(owner_id, sc_dst_parent);
 
+	/* Keep names unique. */
+	collection_name_check(owner_id, sc_src);
+
 	return true;
 }
 
@@ -663,6 +678,9 @@ bool BKE_collection_move_into(const ID *owner_id, SceneCollection *sc_dst, Scene
 	BKE_layer_collection_resync(owner_id, sc_src_parent);
 	BKE_layer_collection_resync(owner_id, sc_dst);
 
+	/* Keep names unique. */
+	collection_name_check(owner_id, sc_src);
+
 	return true;
 }
 

tests/python/view_layer/CMakeLists.txt

@@ -62,7 +62,8 @@ endmacro()
 
 VIEW_LAYER_TEST(active_collection)
 VIEW_LAYER_TEST(background_set)
-VIEW_LAYER_TEST(collection_rename)
+VIEW_LAYER_TEST(collection_rename_a)
+VIEW_LAYER_TEST(collection_rename_b)
 VIEW_LAYER_TEST(evaluation_render_settings_a)
 VIEW_LAYER_TEST(evaluation_render_settings_b)
 VIEW_LAYER_TEST(evaluation_render_settings_c)

tests/python/view_layer/test_collection_rename_b.py

@@ -0,0 +1,58 @@
+# ############################################################
+# Importing - Same For All Render Layer Tests
+# ############################################################
+
+import unittest
+import os
+import sys
+
+from view_layer_common import *
+
+
+# ############################################################
+# Testing
+# ############################################################
+
+class UnitTesting(ViewLayerTesting):
+    def setup_collections(self):
+        import bpy
+        scene = bpy.context.scene
+
+        master = scene.master_collection
+        one = master.collections[0]
+        two = master.collections.new()
+        sub = two.collections.new(one.name)
+
+        self.assertEqual(one.name, sub.name)
+
+        lookup = {
+            'master': master,
+            'one': one,
+            'two': two,
+            'sub': sub,
+        }
+        return lookup
+
+    def test_move_above(self):
+        collections = self.setup_collections()
+        collections['sub'].move_above(collections['one'])
+        self.assertNotEqual(collections['one'].name, collections['sub'].name)
+
+    def test_move_below(self):
+        collections = self.setup_collections()
+        collections['sub'].move_below(collections['one'])
+        self.assertNotEqual(collections['one'].name, collections['sub'].name)
+
+    def test_move_into(self):
+        collections = self.setup_collections()
+        collections['sub'].move_into(collections['master'])
+        self.assertNotEqual(collections['one'].name, collections['sub'].name)
+
+
+# ############################################################
+# Main - Same For All Render Layer Tests
+# ############################################################
+
+if __name__ == '__main__':
+    UnitTesting._extra_arguments = setup_extra_arguments(__file__)
+    unittest.main()