Call proxy methods from alias_attribute generated methods

This commit changes bodies of methods generated by `alias_attribute`
along with generating these methods lazily.

Previously the body of the `alias_attribute :new_title, :title` was
`def new_title; title; end`. This commit changes it to
`def new_title; attribute("title"); end`.

This allows for `alias_attribute` to be used to alias attributes named
with a reserved names like `id`:
```ruby
  class Topic < ActiveRecord::Base
    self.primary_key = :title
    alias_attribute :id_value, :id
  end

  Topic.new.id_value # => 1
```

activemodel/lib/active_model/attribute_methods.rb

@@ -203,34 +203,46 @@ 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)
-        ActiveSupport::CodeGenerator.batch(self, __FILE__, __LINE__) do |code_generator|
-          attribute_method_patterns.each do |pattern|
-            method_name = pattern.method_name(new_name).to_s
-            target_name = pattern.method_name(old_name).to_s
-            parameters = pattern.parameters
+        eagerly_generate_alias_attribute_methods(new_name, old_name)
+      end
 
-            mangled_name = target_name
-            unless NAME_COMPILABLE_REGEXP.match?(target_name)
-              mangled_name = "__temp__#{target_name.unpack1("h*")}"
-            end
+      def eagerly_generate_alias_attribute_methods(new_name, old_name) # :nodoc:
+        ActiveSupport::CodeGenerator.batch(generated_attribute_methods, __FILE__, __LINE__) do |code_generator|
+          generate_alias_attribute_methods(code_generator, new_name, old_name)
+        end
+      end
 
-            code_generator.define_cached_method(method_name, as: mangled_name, namespace: :alias_attribute) do |batch|
-              body = if CALL_COMPILABLE_REGEXP.match?(target_name)
-                "self.#{target_name}(#{parameters || ''})"
-              else
-                call_args = [":'#{target_name}'"]
-                call_args << parameters if parameters
-                "send(#{call_args.join(", ")})"
-              end
+      def generate_alias_attribute_methods(code_generator, new_name, old_name)
+        attribute_method_patterns.each do |pattern|
+          alias_attribute_method_definition(code_generator, pattern, new_name, old_name)
+        end
+      end
 
-              modifier = pattern.parameters == FORWARD_PARAMETERS ? "ruby2_keywords " : ""
+      def alias_attribute_method_definition(code_generator, pattern, new_name, old_name) # :nodoc:
+        method_name = pattern.method_name(new_name).to_s
+        target_name = pattern.method_name(old_name).to_s
+        parameters = pattern.parameters
+        mangled_name = target_name
 
-              batch <<
-                "#{modifier}def #{mangled_name}(#{parameters || ''})" <<
-                body <<
-                "end"
-            end
+        unless NAME_COMPILABLE_REGEXP.match?(target_name)
+          mangled_name = "__temp__#{target_name.unpack1("h*")}"
+        end
+
+        code_generator.define_cached_method(method_name, as: mangled_name, namespace: :alias_attribute) do |batch|
+          body = if CALL_COMPILABLE_REGEXP.match?(target_name)
+            "self.#{target_name}(#{parameters || ''})"
+          else
+            call_args = [":'#{target_name}'"]
+            call_args << parameters if parameters
+            "send(#{call_args.join(", ")})"
           end
+
+          modifier = parameters == FORWARD_PARAMETERS ? "ruby2_keywords " : ""
+
+          batch <<
+            "#{modifier}def #{mangled_name}(#{parameters || ''})" <<
+            body <<
+            "end"
         end
       end
 

activerecord/lib/active_record/attribute_methods.rb

@@ -44,11 +44,68 @@ def initialize_generated_modules # :nodoc:
         @generated_attribute_methods = const_set(:GeneratedAttributeMethods, GeneratedAttributeMethods.new)
         private_constant :GeneratedAttributeMethods
         @attribute_methods_generated = false
+        @alias_attributes_mass_generated = false
         include @generated_attribute_methods
 
         super
       end
 
+      def alias_attribute(new_name, old_name)
+        super
+
+        if @alias_attributes_mass_generated
+          ActiveSupport::CodeGenerator.batch(generated_attribute_methods, __FILE__, __LINE__) do |code_generator|
+            generate_alias_attribute_methods(code_generator, new_name, old_name)
+          end
+        end
+      end
+
+      def eagerly_generate_alias_attribute_methods(_new_name, _old_name) # :nodoc:
+        # alias attributes in Active Record are lazily generated
+      end
+
+      def generate_alias_attributes # :nodoc:
+        return if @alias_attributes_mass_generated
+
+        generated_attribute_methods.synchronize do
+          return if @alias_attributes_mass_generated
+          ActiveSupport::CodeGenerator.batch(generated_attribute_methods, __FILE__, __LINE__) do |code_generator|
+            attribute_aliases.each do |new_name, old_name|
+              generate_alias_attribute_methods(code_generator, new_name, old_name)
+            end
+          end
+
+          @alias_attributes_mass_generated = true
+        end
+      end
+
+      def alias_attribute_method_definition(code_generator, pattern, new_name, old_name)
+        method_name = pattern.method_name(new_name).to_s
+        target_name = pattern.method_name(old_name).to_s
+        parameters = pattern.parameters
+        old_name = old_name.to_s
+
+        method_defined = method_defined?(target_name) || private_method_defined?(target_name)
+        manually_defined = method_defined && self.instance_method(target_name).owner != generated_attribute_methods
+        reserved_method_name = ::ActiveRecord::AttributeMethods.dangerous_attribute_methods.include?(target_name)
+
+        if manually_defined && !reserved_method_name
+          aliased_method_redefined_as_well = method_defined_within?(method_name, self)
+          return if aliased_method_redefined_as_well
+
+          ActiveModel.deprecator.warn(
+            "#{self} model aliases `#{old_name}` and has a method called `#{target_name}` defined. " \
+            "Since Rails 7.2 `#{method_name}` will not be calling `#{target_name}` anymore. " \
+            "You may want to additionally define `#{method_name}` to preserve the current behavior."
+          )
+          super
+        else
+          define_proxy_call(code_generator, method_name, pattern.proxy_target, parameters, old_name,
+            namespace: :proxy_alias_attribute
+          )
+        end
+      end
+
       # Generates all the attribute related methods for columns in the database
       # accessors, mutators and query methods.
       def define_attribute_methods # :nodoc:
@@ -67,6 +124,7 @@ def undefine_attribute_methods # :nodoc:
         generated_attribute_methods.synchronize do
           super if defined?(@attribute_methods_generated) && @attribute_methods_generated
           @attribute_methods_generated = false
+          @alias_attributes_mass_generated = false
         end
       end
 
@@ -188,6 +246,7 @@ def inherited(child_class)
           super
           child_class.initialize_generated_modules
           child_class.class_eval do
+            @alias_attributes_mass_generated = false
             @attribute_names = nil
           end
         end

activerecord/lib/active_record/core.rb

@@ -753,6 +753,7 @@ def init_internals
         @strict_loading_mode = :all
 
         klass.define_attribute_methods
+        klass.generate_alias_attributes
       end
 
       def initialize_internals_callback

activerecord/test/cases/attribute_methods_test.rb

@@ -13,6 +13,7 @@
 require "models/contact"
 require "models/keyboard"
 require "models/numeric_data"
+require "models/cpk"
 
 class AttributeMethodsTest < ActiveRecord::TestCase
   include InTimeZone
@@ -30,6 +31,19 @@ def setup
     ActiveRecord::Base.send(:attribute_method_patterns).concat(@old_matchers)
   end
 
+  test "aliasing `id` attribute allows reading the column value" do
+    topic = Topic.create(id: 123_456, title: "title").becomes(TitlePrimaryKeyTopic)
+
+    assert_equal(123_456, topic.id_value)
+  end
+
+  test "aliasing `id` attribute allows reading the column value for a CPK model" do
+    order = ::Cpk::Order.create(id: [1, 123_456])
+
+    assert_not_nil(order.id_value)
+    assert_equal(123_456, order.id_value)
+  end
+
   test "attribute_for_inspect with a string" do
     t = topics(:first)
     t.title = "The First Topic Now Has A Title With\nNewlines And More Than 50 Characters"
@@ -1130,6 +1144,79 @@ def some_method_that_is_not_on_super
     assert_equal "abcd", model.read_attribute_before_type_cast("new_bank_balance")
   end
 
+  ClassWithDeprecatedAliasAttributeBehavior = Class.new(ActiveRecord::Base) do
+    self.table_name = "topics"
+    alias_attribute :subject, :title
+
+    def title_was
+      "overridden_title_was"
+    end
+  end
+
+  test "#alias_attribute with an overridden original method issues a deprecation" do
+    message = <<~MESSAGE.gsub("\n", " ")
+    AttributeMethodsTest::ClassWithDeprecatedAliasAttributeBehavior model aliases `title` and has a method called
+    `title_was` defined. Since Rails 7.2 `subject_was` will not be calling `title_was` anymore.
+    You may want to additionally define `subject_was` to preserve the current behavior.
+    MESSAGE
+
+    obj = assert_deprecated(message, ActiveModel.deprecator) do
+      ClassWithDeprecatedAliasAttributeBehavior.new
+    end
+    obj.title = "hey"
+    assert_equal("hey", obj.subject)
+    assert_equal("overridden_title_was", obj.subject_was)
+  end
+
+  TitleWasOverride = Module.new do
+    def title_was
+      "overridden_title_was"
+    end
+  end
+
+  ClassWithDeprecatedAliasAttributeBehaviorFromModule = Class.new(ActiveRecord::Base) do
+    self.table_name = "topics"
+    include TitleWasOverride
+    alias_attribute :subject, :title
+  end
+
+  test "#alias_attribute with an overridden original method from a module issues a deprecation" do
+    message = <<~MESSAGE.gsub("\n", " ")
+    AttributeMethodsTest::ClassWithDeprecatedAliasAttributeBehaviorFromModule model aliases `title` and has a method
+    called `title_was` defined. Since Rails 7.2 `subject_was` will not be calling `title_was` anymore.
+    You may want to additionally define `subject_was` to preserve the current behavior.
+    MESSAGE
+
+    obj = assert_deprecated(message, ActiveModel.deprecator) do
+      ClassWithDeprecatedAliasAttributeBehaviorFromModule.new
+    end
+    obj.title = "hey"
+    assert_equal("hey", obj.subject)
+    assert_equal("overridden_title_was", obj.subject_was)
+  end
+
+  ClassWithDeprecatedAliasAttributeBehaviorResolved = Class.new(ActiveRecord::Base) do
+    self.table_name = "topics"
+    alias_attribute :subject, :title
+
+    def title_was
+      "overridden_title_was"
+    end
+
+    def subject_was
+      "overridden_subject_was"
+    end
+  end
+
+  test "#alias_attribute with an overridden original method along with an overridden alias method doesn't issue a deprecation" do
+    obj = assert_not_deprecated(ActiveModel.deprecator) do
+      ClassWithDeprecatedAliasAttributeBehaviorResolved.new
+    end
+    obj.title = "hey"
+    assert_equal("hey", obj.subject)
+    assert_equal("overridden_subject_was", obj.subject_was)
+  end
+
   private
     def new_topic_like_ar_class(&block)
       klass = Class.new(ActiveRecord::Base) do

activerecord/test/cases/validations/numericality_validation_test.rb

@@ -5,6 +5,7 @@
 
 class NumericalityValidationTest < ActiveRecord::TestCase
   def setup
+    NumericData.generate_alias_attributes
     @model_class = NumericData.dup
   end
 

activerecord/test/cases/validations/uniqueness_validation_test.rb

@@ -36,6 +36,7 @@ class ReplyWithTitleObject < Reply
   validates_uniqueness_of :content, scope: :title
 
   def title; ReplyTitle.new; end
+  alias heading title
 end
 
 class TopicWithEvent < Topic

activerecord/test/models/cpk/order.rb

@@ -7,6 +7,8 @@ class Order < ActiveRecord::Base
     # to be shared between different databases
     self.primary_key = [:shop_id, :id]
 
+    alias_attribute :id_value, :id
+
     has_many :order_agreements, primary_key: :id
     has_many :books, query_constraints: [:shop_id, :order_id]
     has_one :book, query_constraints: [:shop_id, :order_id]

activerecord/test/models/topic.rb

@@ -144,6 +144,8 @@ def blank?
 
 class TitlePrimaryKeyTopic < Topic
   self.primary_key = :title
+
+  alias_attribute :id_value, :id
 end
 
 module Web