FIX: Import sub-sub-categories (#8810)

This should make the importer more resilient to incomplete or damaged
backups. It will disable some validations and attempt to automatically
repair category permissions before importing.

spec/import_export/importer_spec.rb

@@ -33,17 +33,43 @@ describe ImportExport::Importer do
         .and change { User.count }.by(2)
     end
 
-    it 'categories and groups' do
-      data = import_data.dup
-      data[:topics] = nil
-      data[:users] = nil
+    context 'categories and groups' do
+      it 'works' do
+        data = import_data.dup
+        data[:topics] = nil
+        data[:users] = nil
 
-      expect {
-        import(data)
-      }.to change { Category.count }.by(6)
-        .and change { Group.count }.by(2)
-        .and change { Topic.count }.by(6)
-        .and change { User.count }.by(0)
+        expect {
+          import(data)
+        }.to change { Category.count }.by(6)
+          .and change { Group.count }.by(2)
+          .and change { Topic.count }.by(6)
+          .and change { User.count }.by(0)
+      end
+
+      it 'works with sub-sub-categories' do
+        data = import_data.dup
+
+        # 11 -> 10 -> 15
+        data[:categories].find { |c| c[:id] == 10 }[:parent_category_id] = 11
+        data[:categories].find { |c| c[:id] == 15 }[:parent_category_id] = 10
+
+        expect { import(data) }
+          .to change { Category.count }.by(6)
+          .and change { SiteSetting.max_category_nesting }.from(2).to(3)
+      end
+
+      it 'fixes permissions' do
+        data = import_data.dup
+        data[:categories].find { |c| c[:id] == 10 }[:permissions_params] = { custom_group: 1 }
+        data[:categories].find { |c| c[:id] == 15 }[:permissions_params] = { staff: 1 }
+
+        permissions = data[:categories].find { |c| c[:id] == 10 }[:permissions_params]
+
+        expect { import(data) }
+          .to change { Category.count }.by(6)
+          .and change { permissions[:staff] }.from(nil).to(1)
+      end
     end
 
     it 'categories, groups and users' do