無效參數：升級到Rails 5后出現nil錯誤

Question

我已升級到Rails 5，並且在啟動服務器后必須加載登錄表單。 然后發生此錯誤：

ArgumentError - invalid argument: nil.:
  activerecord (5.0.0.1) lib/active_record/relation/spawn_methods.rb:36:in `merge'
  activerecord (5.0.0.1) lib/active_record/scoping/default.rb:119:in `block (2 levels) in build_default_scope'
  activerecord (5.0.0.1) lib/active_record/scoping/default.rb:117:in `block in build_default_scope'
  activerecord (5.0.0.1) lib/active_record/scoping/default.rb:141:in `evaluate_default_scope'
  activerecord (5.0.0.1) lib/active_record/scoping/default.rb:116:in `build_default_scope'
  activerecord (5.0.0.1) lib/active_record/scoping/named.rb:33:in `default_scoped'
  activerecord (5.0.0.1) lib/active_record/scoping/named.rb:28:in `all'
  activerecord (5.0.0.1) lib/active_record/scoping.rb:24:in `scope_attributes'
  activerecord (5.0.0.1) lib/active_record/scoping.rb:36:in `populate_with_current_scope_attributes'
  activerecord (5.0.0.1) lib/active_record/scoping.rb:43:in `initialize_internals_callback'
  activerecord (5.0.0.1) lib/active_record/core.rb:317:in `initialize'
  activerecord (5.0.0.1) lib/active_record/inheritance.rb:65:in `new'
  devise (4.2.0) app/controllers/devise/sessions_controller.rb:9:in `new'

我認為那似乎是來自Devise？ 搜索后，我發現有人出現相同的錯誤：

Turns it it was a gem which behind the scenes was attempting to do default_scope { nil }, looks like someone implemented protection against that (since it shouldn't really work)

我該怎么辦？

Answer 1

nil不再有效作為merge參數，因為該方法需要一個ActiveRecord_Relation類的參數。

此問題與該Rails PR有關 。 這是在導軌上的分辨率提交 。

為避免此錯誤：

• 在對關系調用之前，請檢查merge屬性，並僅在不為null時附加它。
• 或始終傳遞有效的ActiveRecord_Relation進行merge ，例如，如果實際參數為nil，則使用<ARModel>.all而不是nil。