`WEBrick::HTTPUtils.escape(nil)` raises a confusing exception

lib/webrick/httputils.rb の HTTPUtils.escape と _escape 周辺から始め、報告された nil の挙動を escape_form(nil) と比較します。提案された 3 つの結果を CGI.escape、URI.encode_www_form_component、ERB::Util.url_encode と照らし合わせて確認します。完了には、意図する nil の挙動についての maintainer の判断と、それに対応するカバレッジが必要です。

% irb
> RUBY_VERSION
=> "3.1.2"

> require 'webrick'
> WEBrick::HTTPUtils.escape(nil)
/Users/katsuhiko.yoshida/.rbenv/versions/3.1.2/lib/ruby/gems/3.1.0/gems/webrick-1.7.0/lib/webrick/httputils.rb:444:in `_escape': undefined method `b' for nil:NilClass (NoMethodError)

      str = str.b
               ^^

(omit)

%irb
> RUBY_VERSION
=> "2.7.6"

> WEBrick::HTTPUtils.escape(nil)
Traceback (most recent call last):
        7: from /Users/katsuhiko.yoshida/.rbenv/versions/2.7.6/bin/irb:23:in `<main>'
        6: from /Users/katsuhiko.yoshida/.rbenv/versions/2.7.6/bin/irb:23:in `load'
        5: from /Users/katsuhiko.yoshida/.rbenv/versions/2.7.6/lib/ruby/gems/2.7.0/gems/irb-1.2.6/exe/irb:11:in `<top (required)>'
        4: from (irb):2
        3: from (irb):3:in `rescue in irb_binding'
        2: from /Users/katsuhiko.yoshida/.rbenv/versions/2.7.6/lib/ruby/2.7.0/webrick/httputils.rb:467:in `escape'
        1: from /Users/katsuhiko.yoshida/.rbenv/versions/2.7.6/lib/ruby/2.7.0/webrick/httputils.rb:443:in `_escape'
NoMethodError (undefined method `b' for nil:NilClass)

WEBrick::HTTPUtils.escape_form(nil) is also the same. If the exception was raised in complex situations (e.g. in third party library), it will be difficult to determine the cause (parameter is nil).

My suggestions are following.

1. Raises a builtin exception
   • CGI.escape is this behavior (raises a TypeError)
2. Raises a custom exception
   • Like a EscapeError
3. Returns ""
   • URI.encode_www_form_component and ERB::Util.url_encode are this behavior
   • But, BREAKING CHANGE (doesn't stop)

Thank you for your great work.