Issue #19566 has been updated by jeremyevans0 (Jeremy Evans). I submitted a pull request to document the requires needed, not just for URI, but for Date/DateTime/Time/Shellwords as well: https://github.com/ruby/optparse/pull/54 ---------------------------------------- Bug #19566: OptionParser::on raises unsupported argument type: URI (ArgumentError) but shouldn't https://bugs.ruby-lang.org/issues/19566#change-102649 * Author: jgomo3 (Jesús Gómez) * Status: Open * Priority: Normal * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- The documentation says

OptionParser comes with a few ready-to-use kinds of type coercion. They are .. * URI – Anything accepted by URI.parse

But when I try to use the class `URI` as a coercion class: ``` op = OptionParser.new op.on("--uri URI", URI) ``` I get: `unsupported argument type: URI (ArgumentError)`. The workaround is to register it with `accept`: ``` op = OptionParser.new op.accept(URI, &URI.method(:parse)) op.on("--uri URI", URI) ``` I attached 2 files, the first one `ruby-op-uri-bug.rb` displays the Error. The second one, `ruby-op-uri-workaround.rb` show the proper output. ---Files-------------------------------- ruby-op-uri-bug.rb (340 Bytes) ruby-op-uri-bug-workaround.rb (377 Bytes) -- https://bugs.ruby-lang.org/