Change HTML validator to ignore all errors except unmatched tags (mastodon#10534)

Author: Gargron

app/models/form/admin_settings.rb

@@ -49,7 +49,8 @@ class Form::AdminSettings
 
   attr_accessor(*KEYS)
 
-  validates :site_short_description, :site_description, :site_extended_description, :site_terms, :closed_registrations_message, html: true
+  validates :site_short_description, :site_description, html: { wrap_with: :p }
+  validates :site_extended_description, :site_terms, :closed_registrations_message, html: true
   validates :registrations_mode, inclusion: { in: %w(open approved none) }
   validates :min_invite_role, inclusion: { in: %w(disabled user moderator admin) }
   validates :site_contact_email, :site_contact_username, presence: true

app/validators/html_validator.rb

@@ -1,18 +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)
-    unless errors.empty?
-      record.errors.add(attribute, I18n.t('html_validator.invalid_markup', error: errors.first.to_s))
-    end
+
+    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(str)
-    fragment.errors
+    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