Revert "Revert "Merge pull request rails#49769 from jonathanhefner/active_record-enum-non-column-backed""

This reverts commit b5fe9ec.

Author: jonathanhefner

activerecord/lib/active_record/enum.rb

@@ -167,15 +167,6 @@ def self.extended(base) # :nodoc:
       base.class_attribute(:defined_enums, instance_writer: false, default: {})
     end
 
-    def load_schema! # :nodoc:
-      defined_enums.each_key do |name|
-        unless columns_hash.key?(resolve_attribute_name(name))
-          raise "Unknown enum attribute '#{name}' for #{self.name}. Enums must be" \
-            " backed by a database column."
-        end
-      end
-    end
-
     class EnumType < Type::Value # :nodoc:
       delegate :type, to: :subtype
 
@@ -264,7 +255,13 @@ def _enum(name, values, prefix: nil, suffix: nil, scopes: true, instance_methods
 
         attribute(name, **options)
 
-        decorate_attributes([name]) do |name, subtype|
+        decorate_attributes([name]) do |_name, subtype|
+          if subtype == ActiveModel::Type.default_value
+            raise "Undeclared attribute type for enum '#{name}' in #{self.name}. Enums must be" \
+              " backed by a database column or declared with an explicit type" \
+              " via `attribute`."
+          end
+
           subtype = subtype.subtype if EnumType === subtype
           EnumType.new(name, enum_values, subtype, raise_on_invalid_values: !validate)
         end

activerecord/lib/active_record/model_schema.rb

@@ -596,8 +596,6 @@ def load_schema!
           @columns_hash = columns_hash.freeze
 
           _default_attributes # Precompute to cache DB-dependent attribute types
-
-          super
         end
 
         # Guesses the table name, but does not decorate it with prefix and suffix information.

activerecord/test/cases/enum_test.rb

@@ -1157,15 +1157,28 @@ def self.name
   end
 
   test "raises for attributes with undeclared type" do
-    klass = Class.new(Book) do
-      def self.name; "Book"; end
-      enum :typeless_genre, [:adventure, :comic]
+    klass = assert_deprecated(ActiveRecord.deprecator) do
+      Class.new(Book) do
+        def self.name; "Book"; end
+        enum typeless_genre: [:adventure, :comic]
+      end
     end
 
     error = assert_raises(RuntimeError) do
-      klass.type_for_attribute(:typeless_genre) # load schema
+      klass.type_for_attribute(:typeless_genre)
+    end
+    assert_match "Undeclared attribute type for enum 'typeless_genre' in Book", error.message
+  end
+
+  test "supports attributes declared with a explicit type" do
+    klass = assert_deprecated(ActiveRecord.deprecator) do
+      Class.new(Book) do
+        attribute :my_genre, :integer
+        enum my_genre: [:adventure, :comic]
+      end
     end
-    assert_match "Unknown enum attribute 'typeless_genre'", error.message
+
+    assert_equal :integer, klass.type_for_attribute(:my_genre).type
   end
 
   test "default methods can be disabled by :_instance_methods" do

railties/test/application/test_test.rb

@@ -335,11 +335,14 @@ class UserTest < ActiveSupport::TestCase
 
       app_file "app/models/user.rb", <<-RUBY
         class User < ApplicationRecord
-          enum :type, [:admin, :user]
+          def self.load_schema!
+            super
+            raise "SCHEMA LOADED!"
+          end
         end
       RUBY
 
-      assert_unsuccessful_run "models/user_test.rb", "Unknown enum attribute 'type' for User"
+      assert_unsuccessful_run "models/user_test.rb", "SCHEMA LOADED!"
     end
 
     test "database-dependent attribute types are resolved when parallel tests are run in eager load context" do