Workaround JRuby Nokogiri issue

Author: johnnyshields

Gemfile

@@ -14,3 +14,12 @@ gem 'rubocop-rake', '~> 0.6.0', require: false
 gem 'simplecov', '~> 0.22', require: false
 gem 'simplecov-lcov', '~> 0.8', require: false
 gem 'timecop', '~> 0.9', require: false
+
+# TODO: This can be removed once Nokogiri 1.19.0 is released
+if defined?(RUBY_ENGINE) && RUBY_ENGINE == 'jruby'
+  git_source(:github) do |repo_name|
+    repo_name = "#{repo_name}/#{repo_name}" unless repo_name.include?('/')
+    "https://github.com/#{repo_name}.git"
+  end
+  gem 'nokogiri', github: 'sparklemotion/nokogiri'
+end

UPGRADING.md

@@ -4,7 +4,7 @@
 
 **IMPORTANT: Please read this section carefully as it contains breaking changes!**
 
-### Before upgrading
+### Before Upgrading
 
 Before attempting to upgrade to `2.0.0`:
 - Upgrade your project to minimum Ruby 3.0, JRuby 9.4, or TruffleRuby 22.
@@ -18,6 +18,13 @@ settings.security[:signature_method] = XMLSecurity::Document::RSA_SHA256
 settings.security[:digest_method] = XMLSecurity::Document::SHA256
 ```
 
+### JRuby users should upgrade to JRuby 1.19 or later
+
+JRuby users should upgrade to Nokogiri gem version 1.19 or later, to avoid 
+[this Nokogiri issue affecting how XML is generated on JRuby](https://github.com/sparklemotion/nokogiri/pull/3456).
+This issue is likely not critical for most IdPs, but since it is not tested, it is recommended to upgrade.
+(At time of writing, Nokogiri 1.19 has not been released, but you can use Github repo `main` branch.)
+
 ### Root "OneLogin" namespace changed to "RubySaml"
 
 RubySaml version `2.0.0` changes the root namespace from `OneLogin::RubySaml::` to just `RubySaml::`.