Fix type casting aggregated values on association's attributes

Follow up of #39255.

Previously aggregation functions only use the model's attribute types on
the relation for type cast, this will be looking up association's
attribute and type caster if a column name is table name qualified.

Fixes #39248.

activerecord/lib/active_record/relation/calculations.rb

@@ -281,8 +281,7 @@ def aggregate_column(column_name)
         end
       end
 
-      def operation_over_aggregate_column(column_name, operation, distinct)
-        column = aggregate_column(column_name)
+      def operation_over_aggregate_column(column, operation, distinct)
         operation == "count" ? column.count(distinct) : column.send(operation)
       end
 
@@ -296,7 +295,8 @@ def execute_simple_calculation(operation, column_name, distinct) #:nodoc:
           # PostgreSQL doesn't like ORDER BY when there are no GROUP BY
           relation = unscope(:order).distinct!(false)
 
-          select_value = operation_over_aggregate_column(column_name, operation, distinct)
+          column = aggregate_column(column_name)
+          select_value = operation_over_aggregate_column(column, operation, distinct)
           select_value.distinct = true if operation == "sum" && distinct
 
           relation.select_values = [select_value]
@@ -307,7 +307,7 @@ def execute_simple_calculation(operation, column_name, distinct) #:nodoc:
         result = skip_query_cache_if_necessary { @klass.connection.select_all(query_builder) }
 
         type_cast_calculated_value(result.cast_values.first, operation) do |value|
-          if type = klass.attribute_types[column_name.to_s]
+          if type = column.try(:type_caster) || klass.attribute_types[column_name.to_s]
             type.deserialize(value)
           else
             value
@@ -331,8 +331,9 @@ def execute_grouped_calculation(operation, column_name, distinct) #:nodoc:
         }
         group_columns = group_aliases.zip(group_fields)
 
+        column = aggregate_column(column_name)
         column_alias = column_alias_for("#{operation} #{column_name.to_s.downcase}")
-        select_value = operation_over_aggregate_column(column_name, operation, distinct)
+        select_value = operation_over_aggregate_column(column, operation, distinct)
         select_value.as(column_alias)
 
         select_values = [select_value]
@@ -365,8 +366,8 @@ def execute_grouped_calculation(operation, column_name, distinct) #:nodoc:
         end
 
         hash_rows = calculated_data.cast_values(key_types).map! do |row|
-          calculated_data.columns.each_with_object({}).with_index do |(column, hash), i|
-            hash[column] = row[i]
+          calculated_data.columns.each_with_object({}).with_index do |(col_name, hash), i|
+            hash[col_name] = row[i]
           end
         end
 
@@ -377,7 +378,7 @@ def execute_grouped_calculation(operation, column_name, distinct) #:nodoc:
           key = key_records[key] if associated
 
           result[key] = type_cast_calculated_value(row[column_alias], operation) do |value|
-            if type ||= klass.attribute_types[column_name.to_s]
+            if type ||= column.try(:type_caster) || klass.attribute_types[column_name.to_s]
               type.deserialize(value)
             else
               value

activerecord/lib/active_record/relation/query_methods.rb

@@ -1272,6 +1272,9 @@ def arel_column(field)
 
         if klass.columns_hash.key?(field) && (!from || table_name_matches?(from))
           arel_attribute(field)
+        elsif field.match?(/\A\w+\.\w+\z/)
+          table, column = field.split(".")
+          predicate_builder.resolve_arel_attribute(table, column)
         else
           yield field
         end

activerecord/test/cases/calculations_test.rb

@@ -8,6 +8,7 @@
 require "models/edge"
 require "models/organization"
 require "models/possession"
+require "models/author"
 require "models/topic"
 require "models/reply"
 require "models/numeric_data"
@@ -22,7 +23,7 @@
 require "support/stubs/strong_parameters"
 
 class CalculationsTest < ActiveRecord::TestCase
-  fixtures :companies, :accounts, :topics, :speedometers, :minivans, :books, :posts, :comments
+  fixtures :companies, :accounts, :authors, :topics, :speedometers, :minivans, :books, :posts, :comments
 
   def test_should_sum_field
     assert_equal 318, Account.sum(:credit_limit)
@@ -1098,6 +1099,29 @@ def assert_minimum_and_maximum_on_time_attributes(time_class)
     assert_equal expected, actual
     assert_instance_of time_class, actual[true]
     assert_instance_of time_class, actual[true]
+
+    actual = Author.joins(:topics).maximum(:"topics.written_on")
+    assert_equal Time.utc(2004, 7, 15, 14, 28, 0, 9900), actual
+    assert_instance_of time_class, actual
+
+    actual = Author.joins(:topics).minimum(:"topics.written_on")
+    assert_equal Time.utc(2003, 7, 16, 14, 28, 11, 223300), actual
+    assert_instance_of time_class, actual
+
+    expected = {
+      1 => Time.utc(2003, 7, 16, 14, 28, 11, 223300),
+      2 => Time.utc(2004, 7, 15, 14, 28, 0, 9900),
+    }
+
+    actual = Author.joins(:topics).group(:id).maximum(:"topics.written_on")
+    assert_equal expected, actual
+    assert_instance_of time_class, actual[1]
+    assert_instance_of time_class, actual[2]
+
+    actual = Author.joins(:topics).group(:id).minimum(:"topics.written_on")
+    assert_equal expected, actual
+    assert_instance_of time_class, actual[1]
+    assert_instance_of time_class, actual[2]
   end
   private :assert_minimum_and_maximum_on_time_attributes
 

activerecord/test/models/author.rb

@@ -174,6 +174,8 @@ def extension_method; end
   has_many :top_posts, -> { order(id: :asc) }, class_name: "Post"
   has_many :other_top_posts, -> { order(id: :asc) }, class_name: "Post"
 
+  has_many :topics, primary_key: "name", foreign_key: "author_name"
+
   attr_accessor :post_log
   after_initialize :set_post_log