This branch fixes the issues raised in rails#48862. By adding the key and it's values to self.references_values as Rails does when building a where clause, it prevents unneccessary aliasing from taking place and allows a User to successfully use a table_alias in their select query using a Hash.

Author: paulreece

activerecord/lib/active_record/relation/query_methods.rb

@@ -2002,6 +2002,10 @@ def transform_select_hash_values(fields)
           case columns_aliases
           when Hash
             columns_aliases.map do |column, column_alias|
+              if values[:joins]&.include?(key)
+                references = PredicateBuilder.references({ key.to_s => fields[key] })
+                self.references_values |= references unless references.empty?
+              end
               arel_column("#{key}.#{column}") do
                 predicate_builder.resolve_arel_attribute(key.to_s, column)
               end.as(column_alias.to_s)

activerecord/test/cases/relation/select_test.rb

@@ -45,6 +45,21 @@ def test_select_with_hash_array_value_with_not_exists_field
       end
     end
 
+    def test_select_with_hash_and_table_alias
+      post = Post.joins(:comments, :comments_with_extend)
+        .select(
+          :title,
+          posts: { title: :post_title },
+          comments: { body: :comment_body },
+          comments_with_extend: { body: :comment_body_2 }
+        )
+        .take
+
+      assert_equal post.title, post.post_title
+      assert_not_nil post.comment_body
+      assert_not_nil post.comment_body_2
+    end
+
     def test_select_with_invalid_nested_field
       assert_raises(ActiveRecord::StatementInvalid) do
         Post.select(posts: { "UPPER(title)" => :post_title }).take