Incompatibility with rdoc 7.2.0 and ruby 2.6

[nevans]

The current minimum_ruby_version is 2.6, and (for just a little while longer) I still need to support security patches for an old version of gem still needs to support ruby 2.6. I've been using docker run -it -v "$(pwd):$(pwd)" -w "$(pwd)" --rm ruby:2.6 bash for local testing (and GitHub Actions setup/ruby in CI).

But, with rdoc in the Gemfile, bundle install installs the latest version. And, after installing v7.2.0, I get the following error, simply running various gem or bundler commands:

$ gem list rdoc
Error loading RubyGems plugin "/usr/local/bundle/gems/rdoc-7.2.0/lib/rubygems_plugin.rb": hash key "*" is not a Symbol (TypeError)
WARN: Unresolved or ambigious specs during Gem::Specification.reset:
      stringio (>= 0)
      Available/installed versions of this gem:
      - 3.0.6
      - 0.0.2
WARN: Clearing out unresolved specs. Try 'gem cleanup <gem>'
Please report a bug if this causes problems.

*** LOCAL GEMS ***

rdoc (7.2.0, 7.1.0, 6.17.0, default: 6.1.2.1)

Here's the full stacktrace from rake

$ bundle exec rake --trace
TypeError: hash key "*" is not a Symbol
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/markup/inline_parser.rb:38:in `<class:InlineParser>'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/markup/inline_parser.rb:10:in `<top (required)>'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/markup/formatter.rb:13:in `require'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/markup/formatter.rb:13:in `<top (required)>'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/markup/to_joined_paragraph.rb:10:in `require'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/markup/to_joined_paragraph.rb:10:in `<top (required)>'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/markdown.rb:576:in `require_relative'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/markdown.rb:576:in `<class:Markdown>'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/markdown.rb:182:in `<top (required)>'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/text.rb:24:in `require'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/text.rb:24:in `<module:Text>'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/text.rb:11:in `<top (required)>'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/code_object.rb:31:in `require'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/code_object.rb:31:in `<class:CodeObject>'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/code_object.rb:29:in `<top (required)>'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/code_object/method_attr.rb:5:in `require'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/code_object/method_attr.rb:5:in `<top (required)>'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/code_object/any_method.rb:5:in `require'
/usr/local/bundle/gems/rdoc-7.2.0/lib/rdoc/code_object/any_method.rb:5:in `<top (required)>'
/home/nick/src/net-imap/rakelib/rdoc.rake:50:in `require'
/home/nick/src/net-imap/rakelib/rdoc.rake:50:in `<top (required)>'
/usr/local/bundle/gems/rake-13.4.2/lib/rake/rake_module.rb:29:in `load'
/usr/local/bundle/gems/rake-13.4.2/lib/rake/rake_module.rb:29:in `load_rakefile'
/usr/local/bundle/gems/rake-13.4.2/lib/rake/default_loader.rb:11:in `load'
/usr/local/bundle/gems/rake-13.4.2/lib/rake/application.rb:804:in `load_imports'
/usr/local/bundle/gems/rake-13.4.2/lib/rake/application.rb:743:in `raw_load_rakefile'
/usr/local/bundle/gems/rake-13.4.2/lib/rake/application.rb:127:in `block in load_rakefile'
/usr/local/bundle/gems/rake-13.4.2/lib/rake/application.rb:209:in `standard_exception_handling'
/usr/local/bundle/gems/rake-13.4.2/lib/rake/application.rb:126:in `load_rakefile'
/usr/local/bundle/gems/rake-13.4.2/lib/rake/application.rb:83:in `block in run'
/usr/local/bundle/gems/rake-13.4.2/lib/rake/application.rb:209:in `standard_exception_handling'
/usr/local/bundle/gems/rake-13.4.2/lib/rake/application.rb:81:in `run'
/usr/local/bundle/gems/rake-13.4.2/exe/rake:27:in `<top (required)>'
/usr/local/bundle/bin/rake:23:in `load'
/usr/local/bundle/bin/rake:23:in `<top (required)>'
/usr/local/bundle/gems/bundler-2.4.22/lib/bundler/cli/exec.rb:58:in `load'
/usr/local/bundle/gems/bundler-2.4.22/lib/bundler/cli/exec.rb:58:in `kernel_load'
/usr/local/bundle/gems/bundler-2.4.22/lib/bundler/cli/exec.rb:23:in `run'
/usr/local/bundle/gems/bundler-2.4.22/lib/bundler/cli.rb:492:in `exec'
/usr/local/bundle/gems/bundler-2.4.22/lib/bundler/vendor/thor/lib/thor/command.rb:28:in `run'
/usr/local/bundle/gems/bundler-2.4.22/lib/bundler/vendor/thor/lib/thor/invocation.rb:127:in `invoke_command'
/usr/local/bundle/gems/bundler-2.4.22/lib/bundler/vendor/thor/lib/thor.rb:527:in `dispatch'
/usr/local/bundle/gems/bundler-2.4.22/lib/bundler/cli.rb:34:in `dispatch'
/usr/local/bundle/gems/bundler-2.4.22/lib/bundler/vendor/thor/lib/thor/base.rb:584:in `start'
/usr/local/bundle/gems/bundler-2.4.22/lib/bundler/cli.rb:28:in `start'
/usr/local/bundle/gems/bundler-2.4.22/exe/bundle:37:in `block in <top (required)>'
/usr/local/bundle/gems/bundler-2.4.22/lib/bundler/friendly_errors.rb:117:in `with_friendly_errors'
/usr/local/bundle/gems/bundler-2.4.22/exe/bundle:29:in `<top (required)>'
/usr/local/bin/bundle:23:in `load'
/usr/local/bin/bundle:23:in `<main>'

The problem is that ruby 2.6 only hash splatting with ** to work with symbol keys:

$ docker run -it --rm ruby:2.6 ruby -e 'pp({ **{"str" => "str"} })'
-e:1:in `<main>': hash key "str" is not a Symbol (TypeError)
$ docker run -it --rm ruby:2.7 ruby -e 'pp({ **{"str" => "str"} })'
{"str"=>"str"}

So that breaks these lines:

  TOKENS = {
    **WORD_PAIRS.transform_values { [:word_pair, nil] },
    **TAGS.keys.to_h {|tag| ["<#{tag}>", [:open_tag, tag]] },
    **TAGS.keys.to_h {|tag| ["</#{tag}>", [:close_tag, tag]] },
    **CODEBLOCK_TAGS.to_h {|tag| ["<#{tag}>", [:code_start, tag]] },
    **STANDALONE_TAGS.keys.to_h {|tag| ["<#{tag}>", [:standalone_tag, tag]] },
    '{' => [:tidylink_start, nil],
    '}' => [:tidylink_mid, nil],
    '\\' => [:escape, nil],
    '[' => nil # To make `label[url]` scan as separate tokens
  } # :nodoc:

[nevans]

And I see now that the main branch has been updated to minimum required ruby of 2.7. But that isn't tested in CI, either. So I suspect it'll break without anyone noticing, as well.

[nevans]

It certainly would've saved me some time, but I'm guessing that it might not be feasible to release a v7.2.1 that fully unbreaks ruby 2.6.

But, even if a v7.2.1 release were to only partially unbreak ruby 2.6, enough to give a more helpful warning message and allow the rakefiles to load, that would be nice.