Include selects in group query with having clause

When a grouped calculation contains a having clause that references a
selected value, we need to include that selected value in the query.

Postgres doesn't support referencing a selected value in a having
clause, but other databases do; we can skip the test on the pg adapter
but run it for the others.

This was fixed before in 9a298a16, but
the test coverage was lost in 5a05207d.
The fix regressed in 6311975f and was
removed in 97d46c17.

activerecord/lib/active_record/relation/calculations.rb

@@ -282,6 +282,7 @@ def execute_grouped_calculation(operation, column_name, distinct) #:nodoc:
             operation,
             distinct).as(aggregate_alias)
         ]
+        select_values += self.select_values unless having_clause.empty?
 
         select_values.concat group_columns.map { |aliaz, field|
           if field.respond_to?(:as)

activerecord/test/cases/calculations_test.rb

@@ -246,7 +246,8 @@ def test_should_group_by_summed_field_having_condition
   end
 
   def test_should_group_by_summed_field_having_condition_from_select
-    c = Account.select("MIN(credit_limit) AS min_credit_limit").group(:firm_id).having("MIN(credit_limit) > 50").sum(:credit_limit)
+    skip if current_adapter?(:PostgreSQLAdapter)
+    c = Account.select("MIN(credit_limit) AS min_credit_limit").group(:firm_id).having("min_credit_limit > 50").sum(:credit_limit)
     assert_nil       c[1]
     assert_equal 60, c[2]
     assert_equal 53, c[9]