From 4c8c31774a7c44080099f4a9c7e21d76fa097e09 Mon Sep 17 00:00:00 2001
From: ebyrds <emmanuel_pajaro@hotmail.com>
Date: Fri, 23 Nov 2018 23:55:31 +0000
Subject: [PATCH] Raises error when attempting to modify enum values

---
 activerecord/CHANGELOG.md              |  4 ++++
 activerecord/lib/active_record/enum.rb |  1 +
 activerecord/test/cases/enum_test.rb   | 14 ++++++++++++++
 3 files changed, 19 insertions(+)

diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 24a64e9deb..95f9cf6d14 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,7 @@
+*   Values of enum are frozen, raising an error when attempting to modify them.
+
+    *Emmanuel Byrd*
+
 *   Move `ActiveRecord::StatementInvalid` SQL to error property and include binds as separate error property.
 
     `ActiveRecord::ConnectionAdapters::AbstractAdapter#translate_exception_class` now requires `binds` to be passed as the last argument.
diff --git a/activerecord/lib/active_record/enum.rb b/activerecord/lib/active_record/enum.rb
index 3a600835e1..d62cd3f92a 100644
--- a/activerecord/lib/active_record/enum.rb
+++ b/activerecord/lib/active_record/enum.rb
@@ -199,6 +199,7 @@ module ActiveRecord
             klass.scope value_method_name, -> { where(attr => value) }
           end
         end
+        enum_values.freeze
       end
     end
 
diff --git a/activerecord/test/cases/enum_test.rb b/activerecord/test/cases/enum_test.rb
index 867ce7082b..fef06e6edd 100644
--- a/activerecord/test/cases/enum_test.rb
+++ b/activerecord/test/cases/enum_test.rb
@@ -438,6 +438,20 @@ class EnumTest < ActiveRecord::TestCase
     assert_equal ["drafted", "uploaded"], book2.status_change
   end
 
+  test "attempting to modify enum raises error" do
+    e = assert_raises(RuntimeError) do
+      Book.statuses["bad_enum"] = 40
+    end
+
+    assert_match(/can't modify frozen/, e.message)
+
+    e = assert_raises(RuntimeError) do
+      Book.statuses.delete("published")
+    end
+
+    assert_match(/can't modify frozen/, e.message)
+  end
+
   test "declare multiple enums at a time" do
     klass = Class.new(ActiveRecord::Base) do
       self.table_name = "books"