Ruby 3.2.2升级后Rails Scope中Lambda无法接收关键字参数

将应用从Ruby 2.7.5升级至3.2.2（Rails版本为6.0.6.1）后，发现带位置参数+关键字参数的Scope Lambda无法正常接收参数，触发ArgumentError提示参数数量错误。虽然Ruby 3.0有位置参数与关键字参数分离的破坏性变更，但普通方法使用相同签名可正常运行，因此判断问题不在Ruby本身。

示例代码：

class TestClass
  scope :test_scope, lambda do |arg1, arg2:|
    puts arg1
    puts arg2
  end
end

调用时的错误：

> TestClass.test_scope
wrong number of arguments (given 0, expected 1; required keyword: arg2) (ArgumentError)

> TestClass.test_scope('abc')
missing keyword: :arg2 (ArgumentError)

> TestClass.test_scope('abc', arg2: 'def')
wrong number of arguments (given 2, expected 1; required keyword: arg2) (ArgumentError)

更新：完整堆栈跟踪
调用示例：

ExampleClass.test_scope('abc', arg2: 'def')

堆栈跟踪：

ArgumentError: wrong number of arguments (given 2, expected 1; required keyword: arg2)
  /app/app/models/example_class.rb:2:in `block in <class:ExampleClass>'
  /bundle/vendor/ruby/3.2.0/gems/activerecord-6.1.7.3/lib/active_record/relation.rb:411:in `instance_exec'
  /bundle/vendor/ruby/3.2.0/gems/activerecord-6.1.7.3/lib/active_record/relation.rb:411:in `block in _exec_scope'
  /bundle/vendor/ruby/3.2.0/gems/activerecord-6.1.7.3/lib/active_record/relation.rb:804:in `_scoping'
  /bundle/vendor/ruby/3.2.0/gems/activerecord-6.1.7.3/lib/active_record/relation.rb:411:in `_exec_scope'
  /bundle/vendor/ruby/3.2.0/gems/activerecord-6.1.7.3/lib/active_record/scoping/named.rb:176:in `block in scope'
  /app/config/initializers/test_init.rb:13:in `<main>'
  /bundle/vendor/ruby/3.2.0/gems/bootsnap-1.11.1/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:39:in `load'
  /bundle/vendor/ruby/3.2.0/gems/bootsnap-1.11.1/lib/bootsnap/load_path_cache/core_ext/kernel_require.rb:39:in `load'
  /bundle/vendor/ruby/3.2.0/gems/activesupport-6.1.7.3/lib/active_support/dependencies.rb:326:in `block in load'
  /bundle/vendor/ruby/3.2.0/gems/activesupport-6.1.7.3/lib/active_support/dependencies.rb:299:in `load_dependency'
  /bundle/vendor/ruby/3.2.0/gems/activesupport-6.1.7.3/lib/active_support/dependencies.rb:326:in `load'
  /bundle/vendor/ruby/3.2.0/gems/railties-6.1.7.3/lib/rails/engine.rb:681:in `block in load_config_initializer'
  /bundle/vendor/ruby/3.2.0/gems/activesupport-6.1.7.3/lib/active_support/notifications.rb:205:in `instrument'
  /bundle/vendor/ruby/3.2.0/gems/railties-6.1.7.3/lib/rails/engine.rb:680:in `load_config_initializer'
  /bundle/vendor/ruby/3.2.0/gems/railties-6.1.7.3/lib/rails/engine.rb:634:in `block (2 levels) in <class:Engine>'
  /bundle/vendor/ruby/3.2.0/gems/railties-6.1.7.3/lib/rails/engine.rb:633:in `each'
  /bundle/vendor/ruby/3.2.0/gems/railties-6.1.7.3/lib/rails/engine.rb:633:in `block in <class:Engine>'
  /bundle/vendor/ruby/3.2.0/gems/railties-6.1.7.3/lib/rails/initializable.rb:32:in `instance_exec'
  /bundle/vendor/ruby/3.2.0/gems/railties-6.1.7.3/lib/rails/initializable.rb:32:in `run'
  /bundle/vendor/ruby/3.2.0/gems/railties-6.1.7.3/lib/rails/initializable.rb:61:in `block in run_initializers'
  /usr/local/lib/ruby/3.2.0/tsort.rb:228:in `block in tsort_each'
  /usr/local/lib/ruby/3.2.0/tsort.rb:350:in `block (2 levels) in each_strongly_connected_component'
  /usr/local/lib/ruby/3.2.0/tsort.rb:422:in `block (2 levels) in each_strongly_connected_component_from'
  /usr/local/lib/ruby/3.2.0/tsort.rb:431:in `each_strongly_connected_component_from'
  /usr/local/lib/ruby/3.2.0/tsort.rb:421:in `block in each_strongly_connected_component_from'
  /bundle/vendor/ruby/3.2.0/gems/railties-6.1.7.3/lib/rails/initializable.rb:50:in `each'
  /bundle/vendor/ruby/3.2.0/gems/railties-6.1.7.3/lib/rails/initializable.rb:50:in `tsort_each_child'
  /usr/local/lib/ruby/3.2.0/tsort.rb:415:in `call'
  /usr/local/lib/ruby/3.2.0/tsort.rb:415:in `each_strongly_connected_component_from'
  /usr/local/lib/ruby/3.2.0/tsort.rb:349:in `block in each_strongly_connected_component'
  /usr/local/lib/ruby/3.2.0/tsort.rb:347:in `each'
  /usr/local/lib/ruby/3.2.0/tsort.rb:347:in `call'
  /usr/local/lib/ruby/3.2.0/tsort.rb:347:in `each_strongly_connected_component'
  /usr/local/lib/ruby/3.2.0/tsort.rb:226:in `tsort_each'
  /usr/local/lib/ruby/3.2.0/tsort.rb:205:in `tsort_each'
  /bundle/vendor/ruby/3.2.0/gems/railties-6.1.7.3/lib/rails/initializable.rb:60:in `run_initializers'
  /bundle/vendor/ruby/3.2.0/gems/railties-6.1.7.3/lib/rails/application.rb:391:in `initialize!'
  /app/config/environment.rb:5:in `<top (required)>'
  config.ru:3:in `require_relative'
  config.ru:3:in `block in <main>'
  /bundle/vendor/ruby/3.2.0/gems/rack-2.2.7/lib/rack/builder.rb:116:in `eval'
  /bundle/vendor/ruby/3.2.0/gems/rack-2.2.7/lib/rack/builder.rb:116:in `new_from_string'
  /bundle/vendor/ruby/3.2.0/gems/rack-2.2.7/lib/rack/builder.rb:105:in `load_file'
  /bundle/vendor/ruby/3.2.0/gems/rack-2.2.7/lib/rack/builder.rb:66:in `parse_file'
  /bundle/vendor/ruby/3.2.0/gems/puma-5.6.5/lib/puma/configuration.rb:348:in `load_rackup'
  /bundle/vendor/ruby/3.2.0/gems/puma-5.6.5/lib/puma/configuration.rb:270:in `app'
  /bundle/vendor/ruby/3.2.0/gems/puma-5.6.5/lib/puma/runner.rb:150:in `load_and_bind'
  /bundle/vendor/ruby/3.2.0/gems/puma-5.6.5/lib/puma/single.rb:44:in `run'
  /bundle/vendor/ruby/3.2.0/gems/puma-5.6.5/lib/puma/launcher.rb:193:in `run'
  /bundle/vendor/ruby/3.2.0/gems/puma-5.6.5/lib/puma/cli.rb:81:in `run'
  /bundle/vendor/ruby/3.2.0/gems/puma-5.6.5/bin/puma:10:in `<top (required)>'
  /bundle/vendor/ruby/3.2.0/bin/puma:25:in `load'
  /bundle/vendor/ruby/3.2.0/bin/puma:25:in `<top (required)>'

问题根源在于Rails 6.0.x版本的Active Record对Scope参数的处理逻辑不兼容Ruby 3+的关键字参数分离规则。

从堆栈跟踪可以看到，Active Record的_exec_scope方法通过instance_exec调用Scope的lambda时，会把所有传入的参数（包括关键字参数）作为位置参数传递，而Ruby 3+会严格区分位置参数和关键字参数，导致lambda的参数签名不匹配，触发错误。而普通方法不受影响是因为Ruby直接处理方法调用的参数分离，而Scope的参数经过了Active Record的一层封装。

有两种解决方式：

方式一：修改Scope的参数签名，兼容现有Rails版本 #

把关键字参数改为哈希参数，或者用**kwargs捕获所有关键字参数，避免参数类型不匹配：

方案1：合并为哈希参数 #

class TestClass
  scope :test_scope, lambda do |arg1, kwargs|
    puts arg1
    puts kwargs[:arg2]
  end
end

# 调用方式不变：
TestClass.test_scope('abc', arg2: 'def')

方案2：用**kwargs捕获关键字参数 #

class TestClass
  scope :test_scope, lambda do |arg1, **kwargs|
    puts arg1
    puts kwargs[:arg2]
  end
end

# 调用方式不变：
TestClass.test_scope('abc', arg2: 'def')

方式二：升级Rails版本到6.1.x及以上 #

Rails 6.1版本已经修复了Ruby 3+下关键字参数的兼容问题，Active Record会正确分离位置参数和关键字参数传递给Scope的lambda。升级后可以保留原有的参数签名不变。

内容的提问来源于stack exchange，提问作者Henridv