问题

我们最近将一个客户的应用程序从Rails 4升级到Rails 5。然而，在运行测试套件后，尝试创建对象时出现了以下问题：

失败/错误：
 @ens_response = EnsResponse.create!(
   edi_request_body:    @response.edi_request_body,
   edi_body:            @response.edi_data,
   reject_reason:       @response.attributes.try(:[], :reject_reason).try(:[], :text),
   response_attributes: @response.attributes
 )
 
 Psych::DisallowedClass:
   尝试加载未指定的类：Policy

其中Policy是我们app/models/文件夹中的一个模型。

我们尝试更改YAML文件的加载方式如下：

@service_hash ||= YAML.load_file(
  Rails.root.join('config', 'mcp_services.yml'),
  permitted_classes: [Policy],
  aliases: true
)[Rails.env]

但没有成功。

我们还尝试更改application.rb文件，使用以下行：

config.active_record.yaml_column_permitted_classes = [
  Symbol,
  ActiveSupport::HashWithIndifferentAccess,
  ActionController::Parameters

但只是收到以下错误：

失败/错误：require File.expand_path("../../config/environment", __FILE__)

NoMethodError:
  未定义方法 `yaml_column_permitted_classes=' for ActiveRecord::Base:Class

您有什么想法可能导致这个问题？本地的Psych版本为psych（默认：3.0.2），Rails版本为gem 'rails', '5.2.8'。

提前感谢！

       Failure/Error:
         @ens_response = EnsResponse.create!(
           edi_request_body:    @response.edi_request_body,
           edi_body:            @response.edi_data,
           reject_reason:       @response.attributes.try(:[], :reject_reason).try(:[], :text),
           response_attributes: @response.attributes
         )
       
       Psych::DisallowedClass:
         Tried to load unspecified class: Policy

      @service_hash ||= YAML.load_file(
        Rails.root.join('config', 'mcp_services.yml'),
        permitted_classes: [Policy ],
        aliases: true
      )[Rails.env]

    config.active_record.yaml_column_permitted_classes = [
      Symbol,
      ActiveSupport::HashWithIndifferentAccess,
      ActionController::Parameters

Failure/Error: require File.expand_path("../../config/environment", __FILE__)

NoMethodError:
  undefined method `yaml_column_permitted_classes=' for ActiveRecord::Base:Class

答案1

得分: 1

将以下部分翻译为中文：

"Quick unsafe hack is to set this in application.rb..."

"More involved is to add an initializer in config/initializers. The initializer tells rails what classes to allow when loading yaml."

"config/initializers/yaml_loader.rb"

"Psych::ClassLoader::ALLOWED_PSYCH_CLASSES = [Policy,
ActionController::Parameters,
ActiveSupport::HashWithIndifferentAccess,
ActiveSupport::TimeWithZone,
ActiveSupport::TimeZone,
DateTime,
]"

"module Psych
class ClassLoader
ALLOWED_PSYCH_CLASSES = [] unless defined? ALLOWED_PSYCH_CLASSES
class Restricted < ClassLoader
def initialize classes, symbols
@classes = classes + Psych::ClassLoader::ALLOWED_PSYCH_CLASSES.map(&:to_s)
@symbols = symbols
super()
end
end
end
end"

  config.active_record.use_yaml_unsafe_load = true

Psych::ClassLoader::ALLOWED_PSYCH_CLASSES = [Policy,
                                                  ActionController::Parameters,
                                                  ActiveSupport::HashWithIndifferentAccess,
                                                  ActiveSupport::TimeWithZone,
                                                  ActiveSupport::TimeZone,
                                                  DateTime,
                                                ]
    
    module Psych
      class ClassLoader
        ALLOWED_PSYCH_CLASSES = [] unless defined? ALLOWED_PSYCH_CLASSES
        class Restricted < ClassLoader
          def initialize classes, symbols
            @classes = classes + Psych::ClassLoader::ALLOWED_PSYCH_CLASSES.map(&:to_s)
            @symbols = symbols
            super()
          end
        end
      end
    end

答案2

得分: 0

经过更彻底的调查，发现错误是由于访问 `@response.attributes` 属性引起的，类似于这样：

```ruby
@ens_response = EnsResponse.create!(response_attributes: @response.attributes)

这是因为前述属性是一个包含多个对象的哈希（Hash），其中包括一个名为 policy: 的属性，该属性是来自相同模型类（Policy）的对象，因此 Psych 尝试加载未指定的类引起了错误。

修复方法是将该属性强制转换为 JSON 字符串（因为这是所需的模式行值类型）：

@ens_response = EnsResponse.create!(
  edi_request_body:    @response.edi_request_body,
  edi_body:            @response.edi_data,
  reject_reason:       @response.attributes.try(:[], :reject_reason).try(:[], :text),
  response_attributes: @response.attributes.to_json
)

故事的教训：在序列化之前使用调试器，如 Pry，检查所有项的属性。

<details>
<summary>英文:</summary>

After more thorough investigation, it turns out that the error is being caused by accessing the `@response.attributes` property, something similar to this:

```ruby
@ens_response = EnsResponse.create!(response_attributes: @response.attributes)

It was due the fact that the aforementioned property is Hash, that contains several objects, including a property called policy: that is an object from the same model class (Policy), hence Psych trying to load an unspecified class caused an error.

The fix was to force-convert this property to a JSON string (since that's the schema row value type required):

         @ens_response = EnsResponse.create!(
           edi_request_body:    @response.edi_request_body,
           edi_body:            @response.edi_data,
           reject_reason:       @response.attributes.try(:[], :reject_reason).try(:[], :text),
           response_attributes: @response.attributes.to_json
         )

Moral of the story: Use debuggers such as Pry and check the properties of all items before serialization.