Issue #19756 has been updated by Dan0042 (Daniel DeLorme). While all this is technically true and correct, I am not particularly interested in "what is permitted"; I think "what actually exists in the real world out there" is the only thing worth caring about. The robustness principle is "be conservative in what you do, be liberal in what you accept from others". If there's a website at http://my_god.example.com and ruby cannot connect to it because there's an underscore, then that website fails the first half of robustness principle, and ruby fails the second half. ---------------------------------------- Bug #19756: URI::HTTP.build does not accept a host of `_gateway`, but `URI.parse` will. https://bugs.ruby-lang.org/issues/19756#change-103773 * Author: postmodern (Hal Brodigan) * Status: Open * Priority: Normal * ruby -v: ruby 3.2.2 (2023-03-30 revision e51014f9c0) [x86_64-linux] * Backport: 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- I noticed a difference in behavior between `URI::HTTP.build` and `URI.parse`. `URI::HTTP.build` will not accept `host:` value of `_gateway`, but `URI.parse` will. ## Steps To Reproduce ```ruby URI::HTTP.build(host: "_gateway") ``` vs. ```ruby URI.parse("http://_gateway") ``` ### Expected Results Both raise the same exception, or return the same URI object. ### Actual Results ``` URI::HTTP.build(host: "_gateway") /usr/share/ruby/uri/generic.rb:601:in `check_host': bad component(expected host component): _gateway (URI::InvalidComponentError) from /usr/share/ruby/uri/generic.rb:640:in `host=' from /usr/share/ruby/uri/generic.rb:673:in `hostname=' from /usr/share/ruby/uri/generic.rb:190:in `initialize' from /usr/share/ruby/uri/generic.rb:136:in `new' from /usr/share/ruby/uri/generic.rb:136:in `build' from /usr/share/ruby/uri/http.rb:61:in `build' from (irb):2:in `<main>' from /usr/local/share/gems/gems/irb-1.7.0/exe/irb:9:in `<top (required)>' from /usr/local/bin/irb:25:in `load' from /usr/local/bin/irb:25:in `<main>' ``` ``` URI.parse("https://_gateway") # => #<URI::HTTPS https://_gateway> ``` ## Additional Information ``` $ gem list uri uri (default: 0.12.1) ``` -- https://bugs.ruby-lang.org/