Ensure target is an attribute for alias_attribute

activemodel/lib/active_model/attribute_methods.rb

@@ -203,7 +203,7 @@ def attribute_method_affix(*affixes)
       #   person.nickname_short? # => true
       def alias_attribute(new_name, old_name)
         self.attribute_aliases = attribute_aliases.merge(new_name.to_s => old_name.to_s)
-        local_attribute_aliases[new_name.to_s] = old_name.to_s
+        self.local_attribute_aliases = local_attribute_aliases.merge(new_name.to_s => old_name.to_s)
         eagerly_generate_alias_attribute_methods(new_name, old_name)
       end
 
@@ -370,6 +370,8 @@ def local_attribute_aliases # :nodoc:
       end
 
       private
+        attr_writer :local_attribute_aliases # :nodoc:
+
         def inherited(base) # :nodoc:
           super
           base.class_eval do

activerecord/lib/active_record/attribute_methods.rb

@@ -91,7 +91,18 @@ def alias_attribute_method_definition(code_generator, pattern, new_name, old_nam
           !self.instance_method(target_name).owner.is_a?(GeneratedAttributeMethods)
         reserved_method_name = ::ActiveRecord::AttributeMethods.dangerous_attribute_methods.include?(target_name)
 
-        if manually_defined && !reserved_method_name
+        if !abstract_class? && !has_attribute?(old_name)
+          # We only need to issue this deprecation warning once, so we issue it when defining the original reader method.
+          should_warn = target_name == old_name
+          if should_warn
+            ActiveRecord.deprecator.warn(
+              "#{self} model aliases `#{old_name}`, but #{old_name} is not an attribute. " \
+              "Starting in Rails 7.2 `, alias_attribute with non-attribute targets will raise. " \
+              "Use `alias_method :#{new_name}`, :#{old_name} or define the method manually."
+            )
+          end
+          super
+        elsif manually_defined && !reserved_method_name
           aliased_method_redefined_as_well = method_defined_within?(method_name, self)
           return if aliased_method_redefined_as_well
 

activerecord/test/cases/attribute_methods_test.rb

@@ -4,6 +4,7 @@
 require "models/minimalistic"
 require "models/developer"
 require "models/auto_id"
+require "models/author"
 require "models/boolean"
 require "models/computer"
 require "models/topic"
@@ -1316,6 +1317,94 @@ class ChildWithDeprecatedBehaviorResolved < ClassWithDeprecatedAliasAttributeBeh
     assert_equal 123_456, object.id_value
   end
 
+  ClassWithGeneratedAttributeMethodTarget = Class.new(ActiveRecord::Base) do
+    self.table_name = "topics"
+    alias_attribute :saved_title, :title_in_database
+  end
+
+  test "#alias_attribute with an _in_database method issues a deprecation warning" do
+    message = <<~MESSAGE.gsub("\n", " ")
+    AttributeMethodsTest::ClassWithGeneratedAttributeMethodTarget model aliases `title_in_database`, but title_in_database is not an attribute.
+    Starting in Rails 7.2 `, alias_attribute with non-attribute targets will raise. Use `alias_method :saved_title`, :title_in_database or define the method manually.
+    MESSAGE
+
+    obj = assert_deprecated(message, ActiveRecord.deprecator) do
+      ClassWithGeneratedAttributeMethodTarget.new
+    end
+    obj.title = "A river runs through it"
+    assert_nil obj.saved_title
+    obj.save
+    assert_equal "A river runs through it", obj.saved_title
+  end
+
+  ClassWithEnumMethodTarget = Class.new(ActiveRecord::Base) do
+    self.table_name = "books"
+
+    attribute :status, :string
+    enum status: {
+      pending: "0",
+      completed: "1",
+    }
+    alias_attribute :is_pending?, :pending?
+  end
+
+  test "#alias_attribute with enum method issues a deprecation warning" do
+    message = <<~MESSAGE.gsub("\n", " ")
+    AttributeMethodsTest::ClassWithEnumMethodTarget model aliases `pending?`, but pending? is not an attribute.
+    Starting in Rails 7.2 `, alias_attribute with non-attribute targets will raise.
+    Use `alias_method :is_pending?`, :pending? or define the method manually.
+    MESSAGE
+
+    obj = assert_deprecated(message, ActiveRecord.deprecator) do
+      ClassWithEnumMethodTarget.new
+    end
+    obj.status = "pending"
+    assert_predicate obj, :pending?
+    assert_predicate obj, :is_pending?
+  end
+
+  ClassWithAssociationTarget = Class.new(ActiveRecord::Base) do
+    self.table_name = "books"
+    belongs_to :author
+
+    alias_attribute :written_by, :author
+  end
+
+  test "#alias_attribute with an association method issues a deprecation warning" do
+    message = <<~MESSAGE.gsub("\n", " ")
+    AttributeMethodsTest::ClassWithAssociationTarget model aliases `author`, but author is not an attribute.
+    Starting in Rails 7.2 `, alias_attribute with non-attribute targets will raise.
+    Use `alias_method :written_by`, :author or define the method manually.
+    MESSAGE
+
+    obj = assert_deprecated(message, ActiveRecord.deprecator) do
+      ClassWithAssociationTarget.new
+    end
+    obj.author = Author.new(name: "Octavia E. Butler")
+    assert_equal "Octavia E. Butler", obj.written_by.name
+  end
+
+  ClassWithAliasedManuallyDefinedMethod = Class.new(ActiveRecord::Base) do
+    self.table_name = "books"
+    alias_attribute :print, :publish
+
+    def publish
+      "Publishing!"
+    end
+  end
+
+  test "#alias_attribute with a manually defined method issues a deprecation warning" do
+    message = <<~MESSAGE.gsub("\n", " ")
+    AttributeMethodsTest::ClassWithAliasedManuallyDefinedMethod model aliases `publish`, but publish is not an attribute.
+    Starting in Rails 7.2 `, alias_attribute with non-attribute targets will raise.
+    Use `alias_method :print`, :publish or define the method manually.
+    MESSAGE
+
+    assert_deprecated(message, ActiveRecord.deprecator) do
+      ClassWithAliasedManuallyDefinedMethod.new
+    end
+  end
+
   private
     def new_topic_like_ar_class(&block)
       klass = Class.new(ActiveRecord::Base) do