Fix UUID primary key with default nil in legacy migration

UUID primary key with no default value feature (#10404, #18206) was lost
in legacy migration caused by #25395 got merged. Restore the feature
again in legacy migration.

2 files changed, 20 insertions, 1 deletions

diff --git a/activerecord/lib/active_record/migration/compatibility.rb b/activerecord/lib/active_record/migration/compatibility.rb
index 2904634eb7..a5d8893634 100644
--- a/activerecord/lib/active_record/migration/compatibility.rb
+++ b/activerecord/lib/active_record/migration/compatibility.rb
@@ -16,7 +16,7 @@ module ActiveRecord
       class V5_0 < V5_1
         def create_table(table_name, options = {})
           if adapter_name == "PostgreSQL"
-            if options[:id] == :uuid && !options[:default]
+            if options[:id] == :uuid && !options.key?(:default)
               options[:default] = "uuid_generate_v4()"
             end
           end
diff --git a/activerecord/test/cases/adapters/postgresql/uuid_test.rb b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
index 29052126d2..4655cd1d20 100644
--- a/activerecord/test/cases/adapters/postgresql/uuid_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/uuid_test.rb
@@ -283,6 +283,25 @@ class PostgresqlUUIDTestNilDefault < ActiveRecord::PostgreSQLTestCase
       schema = dump_table_schema "pg_uuids"
       assert_match(/\bcreate_table "pg_uuids", id: :uuid, default: nil/, schema)
     end
+
+    def test_schema_dumper_for_uuid_primary_key_with_default_nil_in_legacy_migration
+      @verbose_was = ActiveRecord::Migration.verbose
+      ActiveRecord::Migration.verbose = false
+
+      migration = Class.new(ActiveRecord::Migration[5.0]) do
+        def version; 101 end
+        def migrate(x)
+          create_table("pg_uuids_4", id: :uuid, default: nil)
+        end
+      end.new
+      ActiveRecord::Migrator.new(:up, [migration]).migrate
+
+      schema = dump_table_schema "pg_uuids_4"
+      assert_match(/\bcreate_table "pg_uuids_4", id: :uuid, default: nil/, schema)
+    ensure
+      drop_table "pg_uuids_4"
+      ActiveRecord::Migration.verbose = @verbose_was
+    end
   end
 end