Gab Social. All are welcome.

app/validators/html_validator.rb

@@ -0,0 +1,20 @@
+# frozen_string_literal: true
+
+class HtmlValidator < ActiveModel::EachValidator
+  ERROR_RE = /Opening and ending tag mismatch|Unexpected end tag/
+
+  def validate_each(record, attribute, value)
+    return if value.blank?
+
+    errors = html_errors(value)
+
+    record.errors.add(attribute, I18n.t('html_validator.invalid_markup', error: errors.first.to_s)) unless errors.empty?
+  end
+
+  private
+
+  def html_errors(str)
+    fragment = Nokogiri::HTML.fragment(options[:wrap_with] ? "<#{options[:wrap_with]}>#{str}</#{options[:wrap_with]}>" : str)
+    fragment.errors.select { |error| ERROR_RE =~ error.message }
+  end
+end