Prevent deleting asset on step update

app/controllers/steps_controller.rb

@@ -563,7 +563,12 @@ class StepsController < ApplicationController
         for pos, attrs in params[key] do
           if attrs[:_destroy] == '1'
             if attrs[:id].present?
-              attr_params[pos] = { id: attrs[:id], _destroy: '1' }
+              asset = Asset.find_by_id(attrs[:id])
+              if asset.try(&:locked?)
+                asset.errors.add(:base, 'This file is locked.')
+              else
+                attr_params[pos] = { id: attrs[:id], _destroy: '1' }
+              end
             end
             params[key].delete(pos)
           elsif has_destroy_params(params[key][pos])

app/models/asset.rb

@@ -25,7 +25,6 @@ class Asset < ActiveRecord::Base
   do_not_validate_attachment_file_type :file
 
   before_file_post_process :allow_styles_on_images
-  before_destroy :check_if_locked
 
   # Asset validation
   # This could cause some problems if you create empty asset and want to
@@ -453,8 +452,4 @@ class Asset < ActiveRecord::Base
 
     self.file = data
   end
-
-  def check_if_locked
-    return false if locked?
-  end
 end

app/views/steps/_form_assets.html.erb

@@ -3,8 +3,10 @@
     <span class="glyphicon glyphicon-file"></span>
     <%= t("protocols.steps.new.asset_panel_title") %>
     <div class="pull-right">
-      <%= ff.remove_nested_fields_link do %>
-        <span class="glyphicon glyphicon-remove"></span>
+      <% unless ff.object.file.exists? && ff.object.locked? %>
+        <%= ff.remove_nested_fields_link do %>
+          <span class="glyphicon glyphicon-remove"></span>
+        <% end %>
       <% end %>
     </div>
   </div>
@@ -23,4 +25,4 @@
       <%= ff.file_field :file %>
     <% end %>
   </div>
-</div>
+</div>