incorrect_length_validation: ignore STI models

lib/active_record_doctor/detectors/incorrect_length_validation.rb

@@ -36,6 +36,9 @@ def detect
             model_maximum = maximum_allowed_by_validations(model, column.name.to_sym)
             next if model_maximum == column.limit
 
+            # Add violation only to the root model of STI.
+            next if (model_maximum.nil? || column.limit.nil?) && sti_subclass?(model)
+
             problem!(
               model: model.name,
               attribute: column.name,
@@ -55,6 +58,11 @@ def maximum_allowed_by_validations(model, column)
         end
         length_validator ? length_validator.options[:maximum] : nil
       end
+
+      def sti_subclass?(model)
+        model.columns_hash.include?(model.inheritance_column.to_s) &&
+          model.base_class != model
+      end
     end
   end
 end

test/active_record_doctor/detectors/incorrect_length_validation_test.rb

@@ -50,6 +50,20 @@ def test_no_validation_and_limit_is_error
     OUTPUT
   end
 
+  def test_sti_subclasses_are_ignored
+    Context.create_table(:users) do |t|
+      t.string :email, limit: 64
+      t.string :type, null: false
+    end.define_model do
+    end
+
+    Context.define_model(:Client, Context::User)
+
+    assert_problems(<<~OUTPUT)
+      the schema limits users.email to 64 characters but there's no length validator on Context::User.email - remove the database limit or add the validator
+    OUTPUT
+  end
+
   def test_no_validation_and_no_limit_is_ok
     require_arbitrary_long_text_columns!