Remove deprecated support to passing a class to `:class_name` on associations

activerecord/CHANGELOG.md

+*   Remove deprecated support to passing a class to `:class_name` on associations.
+
+    *Rafael Mendonça França*
+
 *   Remove deprecated argument `default` from `index_name_exists?`.
 
     *Rafael Mendonça França*

activerecord/lib/active_record/associations.rb

@@ -1848,7 +1848,7 @@ def has_and_belongs_to_many(name, scope = nil, **options, &extension)
 
           builder = Builder::HasAndBelongsToMany.new name, self, options
 
-          join_model = ActiveSupport::Deprecation.silence { builder.through_model }
+          join_model = builder.through_model
 
           const_set join_model.name, join_model
           private_constant join_model.name
@@ -1877,7 +1877,7 @@ def destroy_associations
             hm_options[k] = options[k] if options.key? k
           end
 
-          ActiveSupport::Deprecation.silence { has_many name, scope, hm_options, &extension }
+          has_many name, scope, hm_options, &extension
           _reflections[name.to_s].parent_reflection = habtm_reflection
         end
       end

activerecord/lib/active_record/reflection.rb

@@ -431,14 +431,7 @@ def initialize(name, scope, options, active_record)
         @association_scope_cache = Concurrent::Map.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:
-            `#{macro} :#{name}, class_name: '#{options[:class_name]}'`
-          MSG
+          raise ArgumentError, "A class was passed to `:class_name` but we are expecting a string."
         end
       end
 

activerecord/test/cases/associations/has_and_belongs_to_many_associations_test.rb

@@ -88,12 +88,6 @@ class DeveloperWithSymbolClassName < Developer
   has_and_belongs_to_many :projects, class_name: :ProjectWithSymbolsForKeys
 end
 
-ActiveSupport::Deprecation.silence do
-  class DeveloperWithConstantClassName < Developer
-    has_and_belongs_to_many :projects, class_name: ProjectWithSymbolsForKeys
-  end
-end
-
 class DeveloperWithExtendOption < Developer
   module NamedExtension
     def category
@@ -954,13 +948,6 @@ def test_with_symbol_class_name
     end
   end
 
-  def test_with_constant_class_name
-    assert_nothing_raised do
-      developer = DeveloperWithConstantClassName.new
-      developer.projects
-    end
-  end
-
   def test_alternate_database
     professor = Professor.create(name: "Plum")
     course = Course.create(name: "Forensics")

activerecord/test/cases/reflection_test.rb

@@ -432,9 +432,10 @@ def test_symbol_for_class_name
   end
 
   def test_class_for_class_name
-    assert_deprecated do
-      assert_predicate ActiveRecord::Reflection.create(:has_many, :clients, nil, { class_name: Client }, Firm), :validate?
+    error = assert_raises(ArgumentError) do
+      ActiveRecord::Reflection.create(:has_many, :clients, nil, { class_name: Client }, Firm)
     end
+    assert_equal "A class was passed to `:class_name` but we are expecting a string.", error.message
   end
 
   def test_join_table