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Deprecate reflection class name to accept a class

The idea of `class_name` as an option of reflection is that passing a
string would allow us to lazy autoload the class.

Using `belongs_to :client, class_name: Customer` is eagerloading models more than necessary
and creating possible circular dependencies.
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1 parent 80bf338 commit 8312a0d22212798864f142b5a94805e0baa6c562 @kirs kirs committed Jan 3, 2017
@@ -1,3 +1,8 @@
+* Deprecate passing a class to the `class_name` because it eagerloads more classes than
+ necessary and potentially creates circular dependencies.
+
+ *Kir Shatrov*
+
* Raise error when has_many through is defined before through association
Fixes #26834
@@ -364,6 +364,17 @@ def initialize(name, scope, options, active_record)
@constructable = calculate_constructable(macro, options)
@association_scope_cache = {}
@scope_lock = Mutex.new
+
+ if options[:class_name] && options[:class_name].class == Class
+ ActiveSupport::Deprecation.warn(<<-MSG.squish)
+ Passing a class to the `class_name` is deprecated and will raise
+ an ArgumentError in Rails 5.2. It eagerloads more classes than
+ necessary and potentially creates circular dependencies.
+
+ Please pass the class name as a string:
+ `belongs_to :client, class_name: 'Company'`
+ MSG
+ end
end
def association_scope_cache(conn, owner)
@@ -86,8 +86,10 @@ class DeveloperWithSymbolClassName < Developer
has_and_belongs_to_many :projects, class_name: :ProjectWithSymbolsForKeys
end
-class DeveloperWithConstantClassName < Developer
- has_and_belongs_to_many :projects, class_name: ProjectWithSymbolsForKeys
+ActiveSupport::Deprecation.silence do
+ class DeveloperWithConstantClassName < Developer
+ has_and_belongs_to_many :projects, class_name: ProjectWithSymbolsForKeys
+ end
end
class DeveloperWithExtendOption < Developer
@@ -404,6 +404,12 @@ def test_symbol_for_class_name
assert_equal Client, Firm.reflect_on_association(:unsorted_clients_with_symbol).klass
end
+ def test_class_for_class_name
+ assert_deprecated do
+ assert_predicate ActiveRecord::Reflection.create(:has_many, :clients, nil, { class_name: Client }, Firm), :validate?
+ end
+ end
+
def test_join_table
category = Struct.new(:table_name, :pluralize_table_names).new("categories", true)
product = Struct.new(:table_name, :pluralize_table_names).new("products", true)
@@ -5,7 +5,7 @@ class User < ActiveRecord::Base
has_secure_token :auth_token
has_and_belongs_to_many :jobs_pool,
- class_name: Job,
+ class_name: "Job",
join_table: "jobs_pool"
end

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