Revert "Merge pull request #38737 from ak15/active_record_enum"

This reverts commit f265e0ddb1, reversing
changes made to 08dfa9212d.

Reverted due to surprising behavior for applications. We need to
deprecate this behavior first instead of raising by default.

activerecord/CHANGELOG.md

@@ -34,22 +34,6 @@
 
     *Dylan Thacker-Smith*
 
-*   Raise error when non-existent enum used in query.
-
-    This change will raise an error when a non-existent enum is passed to a query.
-    Previously with MySQL this would return an unrelated record. Fixes #38687.
-
-    ```ruby
-    class User < ActiveRecord::Base
-      enum status: { active: 0, non_active: 1 }
-    end
-
-    User.where(status: :non_existing_status)
-    => ArgumentError ('non_existing_status' is not a valid status)
-    ```
-
-    *Atul Kanswal*
-
 *   Dump the schema or structure of a database when calling `db:migrate:name`.
 
     In previous versions of Rails, `rails db:migrate` would dump the schema of the database. In Rails 6, that holds true (`rails db:migrate` dumps all databases' schemas), but `rails db:migrate:name` does not share that behavior.

activerecord/lib/active_record/enum.rb

@@ -140,7 +140,6 @@ module ActiveRecord
       end
 
       def serialize(value)
-        assert_valid_value(value)
         mapping.fetch(value, value)
       end
 

activerecord/test/cases/enum_test.rb

@@ -59,7 +59,6 @@ class EnumTest < ActiveRecord::TestCase
     assert_not_equal @book, Book.where(status: [written]).first
     assert_not_equal @book, Book.where("status <> ?", published).first
     assert_equal @book, Book.where("status <> ?", written).first
-    assert_empty Book.where(status: nil)
   end
 
   test "find via where with symbols" do
@@ -70,8 +69,6 @@ class EnumTest < ActiveRecord::TestCase
     assert_not_equal @book, Book.where.not(status: :published).first
     assert_equal @book, Book.where.not(status: :written).first
     assert_equal books(:ddd), Book.where(read_status: :forgotten).first
-    exception = assert_raises(ArgumentError) { Book.where(status: :not_defined).first }
-    assert_match(/'not_defined' is not a valid status/, exception.message)
   end
 
   test "find via where with strings" do
@@ -82,8 +79,6 @@ class EnumTest < ActiveRecord::TestCase
     assert_not_equal @book, Book.where.not(status: "published").first
     assert_equal @book, Book.where.not(status: "written").first
     assert_equal books(:ddd), Book.where(read_status: "forgotten").first
-    exception = assert_raises(ArgumentError) { Book.where(status: "not_defined").first }
-    assert_match(/'not_defined' is not a valid status/, exception.message)
   end
 
   test "build from scope" do