Merge pull request #39292 from kamipo/type_cast_pluck_without_table_name_qualified

Type cast `pluck` values for table name unqalified column in joins tables

activerecord/lib/active_record/associations/join_dependency.rb

@@ -131,6 +131,10 @@ def apply_column_aliases(relation)
         relation._select!(-> { aliases.columns })
       end
 
+      def each(&block)
+        join_root.each(&block)
+      end
+
       protected
         attr_reader :join_root, :join_type
 

activerecord/lib/active_record/relation/calculations.rb

@@ -410,14 +410,34 @@ def type_for(field, &block)
         @klass.type_for_attribute(field_name, &block)
       end
 
+      def build_join_dependencies
+        join_dependencies = []
+        join_dependencies.unshift construct_join_dependency(
+          select_association_list(joins_values + left_outer_joins_values, join_dependencies), nil
+        )
+      end
+
+      def lookup_cast_type_from_join_dependencies(name, join_dependencies)
+        join_dependencies.each do |join_dependency|
+          join_dependency.each do |join|
+            type = join.base_klass.attribute_types.fetch(name, nil)
+            return type if type
+          end
+        end
+        nil
+      end
+
       def type_cast_pluck_values(result, columns)
+        join_dependencies = nil
         cast_types = if result.columns.size != columns.size
           klass.attribute_types
         else
           columns.map.with_index do |column, i|
             column.try(:type_caster) ||
               klass.attribute_types.fetch(name = result.columns[i]) do
-                result.column_types.fetch(name, Type.default_value)
+                join_dependencies ||= build_join_dependencies
+                lookup_cast_type_from_join_dependencies(name, join_dependencies) ||
+                  result.column_types[name] || Type.default_value
               end
           end
         end

activerecord/test/cases/calculations_test.rb

@@ -729,7 +729,9 @@ def test_pluck_type_cast
     assert_equal [ topic.approved ], relation.pluck(:approved)
     assert_equal [ topic.last_read ], relation.pluck(:last_read)
     assert_equal [ topic.written_on ], relation.pluck(:written_on)
+  end
 
+  def test_pluck_type_cast_with_conflict_column_names
     expected = [
       [Date.new(2004, 4, 15), "unread"],
       [Date.new(2004, 4, 15), "reading"],
@@ -743,6 +745,29 @@ def test_pluck_type_cast
     assert_equal expected, actual
   end
 
+  def test_pluck_type_cast_with_joins_without_table_name_qualified_column
+    assert_pluck_type_cast_without_table_name_qualified_column(Author.joins(:books))
+  end
+
+  def test_pluck_type_cast_with_left_joins_without_table_name_qualified_column
+    assert_pluck_type_cast_without_table_name_qualified_column(Author.left_joins(:books))
+  end
+
+  def test_pluck_type_cast_with_eager_load_without_table_name_qualified_column
+    assert_pluck_type_cast_without_table_name_qualified_column(Author.eager_load(:books))
+  end
+
+  def assert_pluck_type_cast_without_table_name_qualified_column(authors)
+    expected = [
+      [nil, "unread"],
+      ["ebook", "reading"],
+      ["paperback", "read"],
+    ]
+    actual = authors.order(:last_read).where.not("books.last_read": nil).pluck(:format, :last_read)
+    assert_equal expected, actual
+  end
+  private :assert_pluck_type_cast_without_table_name_qualified_column
+
   def test_pluck_with_type_cast_does_not_corrupt_the_query_cache
     topic = topics(:first)
     relation = Topic.where(id: topic.id)