Merge pull request rails#53264 from kamipo/fix_pluck_with_qualified_name_on_loaded

Fix `pluck` with qualified name on loaded relation

Author: kamipo

activerecord/lib/active_record/relation/calculations.rb

@@ -311,8 +311,8 @@ def pluck(*column_names)
         relation.pluck(*column_names)
       else
         model.disallow_raw_sql!(flattened_args(column_names))
-        columns = arel_columns(column_names)
         relation = spawn
+        columns = relation.arel_columns(column_names)
         relation.select_values = columns
         result = skip_query_cache_if_necessary do
           if where_clause.contradiction?

activerecord/lib/active_record/relation/query_methods.rb

@@ -1656,6 +1656,22 @@ def async!
         self
       end
 
+    protected
+      def arel_columns(columns)
+        columns.flat_map do |field|
+          case field
+          when Symbol, String
+            arel_column(field)
+          when Proc
+            field.call
+          when Hash
+            arel_columns_from_hash(field)
+          else
+            field
+          end
+        end
+      end
+
     private
       def async
         spawn.async!
@@ -1943,21 +1959,6 @@ def build_with_join_node(name, kind = Arel::Nodes::InnerJoin)
         ).join_sources.first
       end
 
-      def arel_columns(columns)
-        columns.flat_map do |field|
-          case field
-          when Symbol, String
-            arel_column(field)
-          when Proc
-            field.call
-          when Hash
-            arel_columns_from_hash(field)
-          else
-            field
-          end
-        end
-      end
-
       def arel_columns_from_hash(fields)
         fields.flat_map do |table_name, columns|
           table_name = table_name.name if table_name.is_a?(Symbol)

activerecord/test/cases/calculations_test.rb

@@ -1241,6 +1241,18 @@ def test_pluck_replaces_select_clause
     assert_equal [false, true, true, true, true], takes_relation.pluck(:approved)
   end
 
+  def test_pluck_with_qualified_name_on_loaded
+    topics = Topic.joins(:replies).order(:id)
+
+    assert_not_predicate topics, :loaded?
+    assert_equal [[1, 2], [3, 4]], topics.pluck("topics.id", "replies.id")
+
+    topics.load
+
+    assert_predicate topics, :loaded?
+    assert_equal [[1, 2], [3, 4]], topics.pluck("topics.id", "replies.id")
+  end
+
   def test_pluck_columns_with_same_name
     expected = [["The First Topic", "The Second Topic of the day"], ["The Third Topic of the day", "The Fourth Topic of the day"]]
     actual = Topic.joins(:replies).order(:id)