Merge branch 'blender-v5.0-release'

source/blender/blenloader/intern/readfile.cc

@@ -3094,6 +3094,31 @@ static void read_libblock_undo_restore_at_old_address(FileData *fd, Main *main,
 
   BLI_addtail(new_lb, id_old);
   BLI_addtail(old_lb, id);
+
+  /* In case a library has been re-read, it has added already its own split main to the new Main
+   * (see #direct_link_library code).
+   *
+   * Since we are replacing it with the 'id_old' address, we need to update that Main::curlib
+   * pointer accordingly.
+   *
+   * Note that:
+   *   - This code is only for undo, and on undo we do not re-read regular libraries, only archive
+   *     ones for packed data.
+   *   - The new split main should still be empty at this stage (this code and adding the split
+   *     Main in #direct_link_library are part of the same #read_libblock call).
+   */
+  if (GS(id_old->name) == ID_LI) {
+    Library *lib_old = blender::id_cast<Library *>(id_old);
+    Library *lib = blender::id_cast<Library *>(id);
+    BLI_assert(lib_old->flag & LIBRARY_FLAG_IS_ARCHIVE);
+
+    for (Main *bmain_iter : *fd->bmain->split_mains) {
+      if (bmain_iter->curlib == lib) {
+        BLI_assert(BKE_main_is_empty(bmain_iter));
+        bmain_iter->curlib = lib_old;
+      }
+    }
+  }
 }
 
 static bool read_libblock_undo_restore(