Follow-up to #10776

The name `ActiveModel::AttributeAssignment::UnknownAttributeError` is
too implementation specific so let's move the constant directly under
the ActiveModel namespace.

Also since this constant used to be under the ActiveRecord namespace, to
make the upgrade path easier, let's avoid raising the former constant
when we deal with this error on the Active Record side.

5 files changed, 15 insertions, 14 deletions

diff --git a/activemodel/lib/active_model.rb b/activemodel/lib/active_model.rb
index 58fe08cc11..8aa1b6f664 100644
--- a/activemodel/lib/active_model.rb
+++ b/activemodel/lib/active_model.rb
@@ -50,6 +50,7 @@ module ActiveModel
   eager_autoload do
     autoload :Errors
     autoload :StrictValidationFailed, 'active_model/errors'
+    autoload :UnknownAttributeError, 'active_model/errors'
   end
 
   module Serializers
diff --git a/activemodel/lib/active_model/attribute_assignment.rb b/activemodel/lib/active_model/attribute_assignment.rb
index 356421476c..087d11f708 100644
--- a/activemodel/lib/active_model/attribute_assignment.rb
+++ b/activemodel/lib/active_model/attribute_assignment.rb
@@ -48,16 +48,5 @@ module ActiveModel
         raise UnknownAttributeError.new(self, k)
       end
     end
-
-    # Raised when unknown attributes are supplied via mass assignment.
-    class UnknownAttributeError < NoMethodError
-      attr_reader :record, :attribute
-
-      def initialize(record, attribute)
-        @record = record
-        @attribute = attribute
-        super("unknown attribute '#{attribute}' for #{@record.class}.")
-      end
-    end
   end
 end
diff --git a/activemodel/lib/active_model/errors.rb b/activemodel/lib/active_model/errors.rb
index 8334747615..8a21332cc2 100644
--- a/activemodel/lib/active_model/errors.rb
+++ b/activemodel/lib/active_model/errors.rb
@@ -525,4 +525,15 @@ module ActiveModel
   #   # => ActiveModel::StrictValidationFailed: Name can't be blank
   class StrictValidationFailed < StandardError
   end
+
+  # Raised when unknown attributes are supplied via mass assignment.
+  class UnknownAttributeError < NoMethodError
+    attr_reader :record, :attribute
+
+    def initialize(record, attribute)
+      @record = record
+      @attribute = attribute
+      super("unknown attribute '#{attribute}' for #{@record.class}.")
+    end
+  end
 end
diff --git a/activemodel/test/cases/attribute_assignment_test.rb b/activemodel/test/cases/attribute_assignment_test.rb
index 402caf21f7..64a85e01eb 100644
--- a/activemodel/test/cases/attribute_assignment_test.rb
+++ b/activemodel/test/cases/attribute_assignment_test.rb
@@ -49,7 +49,7 @@ class AttributeAssignmentTest < ActiveModel::TestCase
 
   test "assign non-existing attribute" do
     model = Model.new
-    error = assert_raises(ActiveModel::AttributeAssignment::UnknownAttributeError) do
+    error = assert_raises(ActiveModel::UnknownAttributeError) do
       model.assign_attributes(hz: 1)
     end
 
@@ -59,7 +59,7 @@ class AttributeAssignmentTest < ActiveModel::TestCase
 
   test "assign private attribute" do
     model = Model.new
-    assert_raises(ActiveModel::AttributeAssignment::UnknownAttributeError) do
+    assert_raises(ActiveModel::UnknownAttributeError) do
       model.assign_attributes(metadata: { a: 1 })
     end
   end
diff --git a/activemodel/test/cases/model_test.rb b/activemodel/test/cases/model_test.rb
index 9a8d873ec9..3017f3541b 100644
--- a/activemodel/test/cases/model_test.rb
+++ b/activemodel/test/cases/model_test.rb
@@ -70,7 +70,7 @@ class ModelTest < ActiveModel::TestCase
   end
 
   def test_mixin_initializer_when_args_dont_exist
-    assert_raises(ActiveModel::AttributeAssignment::UnknownAttributeError) do
+    assert_raises(ActiveModel::UnknownAttributeError) do
       SimpleModel.new(hello: 'world')
     end
   end