Fixes #2150 - Text attribute inputs longer than maxlength is silently truncated

app/models/object_manager/attribute/validation/max_length.rb

@@ -0,0 +1,27 @@
+# Copyright (C) 2012-2022 Zammad Foundation, https://zammad-foundation.org/
+
+class ObjectManager::Attribute::Validation::MaxLength < ObjectManager::Attribute::Validation::Backend
+
+  def validate
+    return if value.blank?
+    return if irrelevant_attribute?
+
+    validate_max_length
+  end
+
+  private
+
+  def irrelevant_attribute?
+    %w[input textarea].exclude? attribute.data_type
+  end
+
+  def maxlength
+    attribute.data_option[:maxlength]
+  end
+
+  def validate_max_length
+    return if value.length <= maxlength
+
+    invalid_because_attribute("is longer than the allowed length #{maxlength}")
+  end
+end

spec/models/object_manager/attribute/validation/max_length_spec.rb

@@ -0,0 +1,62 @@
+# Copyright (C) 2012-2022 Zammad Foundation, https://zammad-foundation.org/
+
+require 'rails_helper'
+require 'models/object_manager/attribute/validation/backend_examples'
+
+RSpec.describe ::ObjectManager::Attribute::Validation::MaxLength do
+
+  subject do
+    described_class.new(
+      record:    record,
+      attribute: attribute
+    )
+  end
+
+  let(:record) { build(:user) }
+
+  %w[text textarea].each do |suffix|
+    let(:attribute) { build("object_manager_attribute_#{suffix}") }
+
+    context "with #{suffix} type" do
+      context 'when validation should not be performed' do
+        describe 'for blank value' do
+          let(:value) { nil }
+
+          it_behaves_like 'a validation without errors'
+        end
+
+        describe 'for irrelevant attribute data_type' do
+          let(:value) { 'some_value' }
+
+          before { attribute.data_type = 'select' }
+
+          it_behaves_like 'a validation without errors'
+        end
+      end
+
+      context 'when validation should be performed' do
+        describe "for data_option 'maxlength'" do
+          before { attribute.data_option[:maxlength] = 10 }
+
+          context 'when value is the same as data_option' do
+            let(:value) { 'test valūe' }
+
+            it_behaves_like 'a validation without errors'
+          end
+
+          context 'when value is valid' do
+            let(:value) { 'test' }
+
+            it_behaves_like 'a validation without errors'
+          end
+
+          context 'when value is invalid' do
+            let(:value) { 'long text here' }
+
+            it_behaves_like 'a validation with errors'
+          end
+        end
+      end
+    end
+  end
+end