Address `warning: literal string will be frozen in the future` warnings

[yahonda]

This commit addresses the warning: literal string will be frozen in the future warnings appeared at Rails CI https://buildkite.com/rails/rails-nightly/builds/1122#019263a3-2200-4e62-a6a8-028cffa60aaf

Here are the warnings appeared:

/usr/local/lib/ruby/gems/3.4.0+0/bundler/gems/httpclient-d57cc6d5ffee/lib/httpclient.rb:1256: warning: literal string will be frozen in the future
/usr/local/lib/ruby/gems/3.4.0+0/bundler/gems/httpclient-d57cc6d5ffee/lib/httpclient/http.rb:580: warning: literal string will be frozen in the future
/usr/local/lib/ruby/gems/3.4.0+0/bundler/gems/httpclient-d57cc6d5ffee/lib/httpclient/session.rb:954: warning: literal string will be frozen in the future
/usr/local/lib/ruby/gems/3.4.0+0/bundler/gems/httpclient-d57cc6d5ffee/lib/httpclient/util.rb:71: warning: literal string will be frozen in the future

There should be some warnings remained because Rails CI does not use all of httpclient code. I'll open some pull requests later to address remaining ones.

Ref: https://bugs.ruby-lang.org/issues/20205

[hartator]

I think we should reasonably push back on these new warnings and the restriction itself.

I don't think they realized how big of an impact it will be while negatively impacting performance at least in the short term.

I have added a note: https://bugs.ruby-lang.org/issues/20205#note-55

[hsbt]

I also found warnings by stdlib with @yahonda:

/Users/hsbt/.local/share/rbenv/versions/ruby-dev/lib/ruby/3.4.0+0/open-uri.rb:455: warning: literal string will be frozen in the future
/Users/hsbt/.local/share/rbenv/versions/ruby-dev/lib/ruby/3.4.0+0/logger/log_device.rb:45: warning: literal string will be frozen in the future

@mame found open-uri warning caused by

def set_body_encoding
  if type = self.content_type
    OpenURI::Meta.init(o = '')
    o.meta_add_field('content-type', type)
    @body_encoding = o.encoding
  end
end

from https://github.com/nahi/httpclient/blob/master/lib/httpclient/http.rb#L241

It's hard to fix that from open-uri warnings.

[byroot]

The warning isn't really from open-uri but from passing a literal to a method that mutate the argument.

The fix is to do: OpenURI::Meta.init(o = ''.dup)

[byroot]

An easy way to solve these warnings is to run ruby with --enable-frozen-string-literal --debug-frozen-string-literal, this will include the location where the string was allocated in the FrozenError message.

[jeremy]

Covered other cases in #465

[yahonda]

Rebased master branch to make CI run.

[byroot]

I recommend you add one Ruby with --enable-frozen-string-literal --debug-frozen-string-literal in the CI Matrix.

Also I silenced those warnings when I revamped CI, it should now be removed.

[wyardley]

Will a release be getting cut with these changes soon?

[takkanm]

We are currently planning a new release. Please wait a little longer.