URI Equivalent of encode_www_form_component in Addressable

What is the equivalent method for URI.encode_www_form_component in Addressable::URI?

The closest you can get is to use the #encode_component method. Beware that Addressable will use full percentage mode, and replace a space with %20 instead of +:

Addressable::URI.encode_component('a decoded string with email@example.com', Addressable::URI::CharacterClasses::UNRESERVED)
# => "a%20decoded%20string%20with%20email%40example.com"

URI.encode_www_form_component('a decoded string with email@example.com')
# => "a+decoded+string+with+email%40example.com"

If you compare the two methods that encode a full set of key/value parameters, you will see instead that they behave more similarly:

[15] pry(main)> Addressable::URI.form_encode([["q", "a decoded string with email@example.com"]])
=> "q=a+decoded+string+with+email%40example.com"
[16] pry(main)> URI.encode_www_form([["q", "a decoded string with email@example.com"]])
=> "q=a+decoded+string+with+email%40example.com"

I was actually surprised when I tested it. So I dug into the source code of Addressable, and I found the form_encode method makes an explicit replacement of %20 with +:

escaped_form_values = form_values.map do |(key, value)|
  # Line breaks are CRLF pairs
  [
    self.encode_component(
      key.gsub(/(\r\n|\n|\r)/, "\r\n"),
      CharacterClasses::UNRESERVED
    ).gsub("%20", "+"),
    self.encode_component(
      value.gsub(/(\r\n|\n|\r)/, "\r\n"),
      CharacterClasses::UNRESERVED
    ).gsub("%20", "+")
  ]
end

So here's your options:

1. Use #encode_component as it is
2. Use #encode_component and explicitly replace %20 with + if you need to reproduce the same output
3. Use #form_encode if you have a key/value form fields