Type cast extra select for eager loading

It is not a big issue for common types, since type casting in master
branch is much improved, but strictly speaking eager loading should
respect column types from database like as `find_by_sql` also does.

https://github.com/rails/rails/blob/97c34a55fa0f4e8d51504bd137f6e82155336d9a/activerecord/lib/active_record/querying.rb#L46-L52

Fixes #39605.

activerecord/lib/active_record/associations/join_dependency.rb

@@ -104,8 +104,16 @@ def instantiate(result_set, strict_loading_value, &block)
         model_cache = Hash.new { |h, klass| h[klass] = {} }
         parents = model_cache[join_root]
 
-        column_aliases = aliases.column_aliases join_root
-        column_aliases += explicit_selections(column_aliases, result_set)
+        column_aliases = aliases.column_aliases(join_root)
+        column_names = explicit_selections(column_aliases, result_set)
+
+        if column_names.empty?
+          column_types = {}
+        else
+          column_types = result_set.column_types
+          column_types = column_types.slice(*column_names) unless column_types.empty?
+          column_aliases += column_names.map! { |name| Aliases::Column.new(name, name) }
+        end
 
         message_bus = ActiveSupport::Notifications.instrumenter
 
@@ -117,7 +125,7 @@ def instantiate(result_set, strict_loading_value, &block)
         message_bus.instrument("instantiation.active_record", payload) do
           result_set.each { |row_hash|
             parent_key = primary_key ? row_hash[primary_key] : row_hash
-            parent = parents[parent_key] ||= join_root.instantiate(row_hash, column_aliases, &block)
+            parent = parents[parent_key] ||= join_root.instantiate(row_hash, column_aliases, column_types, &block)
             construct(parent, join_root, row_hash, seen, model_cache, strict_loading_value)
           }
         end
@@ -141,9 +149,9 @@ def each(&block)
 
         def explicit_selections(root_column_aliases, result_set)
           root_names = root_column_aliases.map(&:name).to_set
-          result_set.columns
-            .reject { |n| root_names.include?(n) || n =~ /\At\d+_r\d+\z/ }
-            .map { |n| Aliases::Column.new(n, n) }
+          result_set.columns.each_with_object([]) do |name, result|
+            result << name unless /\At\d+_r\d+\z/.match?(name) || root_names.include?(name)
+          end
         end
 
         def aliases

activerecord/lib/active_record/associations/join_dependency/join_part.rb

@@ -62,8 +62,8 @@ def extract_record(row, column_names_with_alias)
           hash
         end
 
-        def instantiate(row, aliases, &block)
-          base_klass.instantiate(extract_record(row, aliases), &block)
+        def instantiate(row, aliases, column_types = {}, &block)
+          base_klass.instantiate(extract_record(row, aliases), column_types, &block)
         end
       end
     end

activerecord/test/cases/relation/select_test.rb

@@ -25,19 +25,33 @@ def test_reselect_with_default_scope_select
       assert_equal expected, actual
     end
 
+    def test_type_casted_extra_select_with_eager_loading
+      posts = Post.select("posts.id * 1.1 AS foo").eager_load(:comments)
+      assert_equal 1.1, posts.first.foo
+    end
+
     def test_aliased_select_using_as_with_joins_and_includes
       posts = Post.select("posts.id AS field_alias").joins(:comments).includes(:comments)
-      assert_includes posts.first.attributes, "field_alias"
+      assert_equal %w(
+        id author_id title body type legacy_comments_count taggings_with_delete_all_count taggings_with_destroy_count
+        tags_count indestructible_tags_count tags_with_destroy_count tags_with_nullify_count field_alias
+      ), posts.first.attributes.keys
     end
 
     def test_aliased_select_not_using_as_with_joins_and_includes
       posts = Post.select("posts.id field_alias").joins(:comments).includes(:comments)
-      assert_includes posts.first.attributes, "field_alias"
+      assert_equal %w(
+        id author_id title body type legacy_comments_count taggings_with_delete_all_count taggings_with_destroy_count
+        tags_count indestructible_tags_count tags_with_destroy_count tags_with_nullify_count field_alias
+      ), posts.first.attributes.keys
     end
 
     def test_star_select_with_joins_and_includes
       posts = Post.select("posts.*").joins(:comments).includes(:comments)
-      assert_not_includes posts.first.attributes, "posts.*"
+      assert_equal %w(
+        id author_id title body type legacy_comments_count taggings_with_delete_all_count taggings_with_destroy_count
+        tags_count indestructible_tags_count tags_with_destroy_count tags_with_nullify_count
+      ), posts.first.attributes.keys
     end
   end
 end