5 files changed, 43 insertions, 5 deletions
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 16f9db95fc..d39e808f5b 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,10 @@
+*   Fixed a problem where an enum would overwrite values of another enum
+    with the same name in an unrelated class.
+
+    Fixes #14607.
+
+    *Evan Whalen*
+
 *   PostgreSQL and SQLite string columns no longer have a default limit of 255.
 
     Fixes #13435, #9153.
diff --git a/activerecord/lib/active_record/enum.rb b/activerecord/lib/active_record/enum.rb
index 4aa323fb00..167f8b7a49 100644
--- a/activerecord/lib/active_record/enum.rb
+++ b/activerecord/lib/active_record/enum.rb
@@ -65,10 +65,13 @@ module ActiveRecord
   #
   # Where conditions on an enum attribute must use the ordinal value of an enum.
   module Enum
-    DEFINED_ENUMS = {} # :nodoc:
+    def self.extended(base)
+      base.class_attribute(:defined_enums)
+      base.defined_enums = {}
+    end
 
     def enum_mapping_for(attr_name) # :nodoc:
-      DEFINED_ENUMS[attr_name.to_s]
+      defined_enums[attr_name.to_s]
     end
 
     def enum(definitions)
@@ -122,9 +125,8 @@ module ActiveRecord
             klass.send(:detect_enum_conflict!, name, value, true)
             klass.scope value, -> { klass.where name => i }
           end
-
-          DEFINED_ENUMS[name.to_s] = enum_values
         end
+        defined_enums[name.to_s] = enum_values
       end
     end
 
diff --git a/activerecord/lib/active_record/relation/calculations.rb b/activerecord/lib/active_record/relation/calculations.rb
index 45ffb99868..812e3e800a 100644
--- a/activerecord/lib/active_record/relation/calculations.rb
+++ b/activerecord/lib/active_record/relation/calculations.rb
@@ -231,7 +231,7 @@ module ActiveRecord
 
     def execute_simple_calculation(operation, column_name, distinct) #:nodoc:
       # Postgresql doesn't like ORDER BY when there are no GROUP BY
-      relation = reorder(nil)
+      relation = unscope(:order)
 
       column_alias = column_name
 
diff --git a/activerecord/test/cases/calculations_test.rb b/activerecord/test/cases/calculations_test.rb
index db999f90ab..b8de78934e 100644
--- a/activerecord/test/cases/calculations_test.rb
+++ b/activerecord/test/cases/calculations_test.rb
@@ -387,6 +387,20 @@ class CalculationsTest < ActiveRecord::TestCase
     assert_raise(ArgumentError) { Account.count(1, 2, 3) }
   end
 
+  def test_count_with_order
+    assert_equal 6, Account.order(:credit_limit).count
+  end
+
+  def test_count_with_reverse_order
+    assert_equal 6, Account.order(:credit_limit).reverse_order.count
+  end
+
+  def test_count_with_where_and_order
+    assert_equal 1, Account.where(firm_name: '37signals').count
+    assert_equal 1, Account.where(firm_name: '37signals').order(:firm_name).count
+    assert_equal 1, Account.where(firm_name: '37signals').order(:firm_name).reverse_order.count
+  end
+
   def test_should_sum_expression
     # Oracle adapter returns floating point value 636.0 after SUM
     if current_adapter?(:OracleAdapter)
diff --git a/activerecord/test/cases/enum_test.rb b/activerecord/test/cases/enum_test.rb
index 47de3dec98..5157c272ca 100644
--- a/activerecord/test/cases/enum_test.rb
+++ b/activerecord/test/cases/enum_test.rb
@@ -250,4 +250,19 @@ class EnumTest < ActiveRecord::TestCase
     valid_book = klass.new(status: "written")
     assert valid_book.valid?
   end
+
+  test "enums are distinct per class" do
+    Plane = Class.new(ActiveRecord::Base) do
+      enum status: [:grounded, :operational]
+    end
+    assert_equal({ "proposed" => 0, "written" => 1, "published" => 2 }, Book.statuses)
+    assert_equal({ "grounded" => 0, "operational" => 1 }, Plane.statuses)
+  end
+
+  test "enums are inheritable" do
+    Encyclopedia = Class.new(Book) do
+      enum status: [:published, :reprinted]
+    end
+    assert_equal({ "published" => 0, "reprinted" => 1 }, Encyclopedia.statuses)
+  end
 end