End of Life Ruby 3.1 has reached end of life and gets no more fixes. Switch to Ruby 4.0 →

class method

Gem.plugindir

plugindir(install_dir=Gem.dir)

# File tmp/rubies/ruby-3.1.3/lib/rubygems.rb, line 311
def self.plugindir(install_dir=Gem.dir)
  File.join install_dir, "plugins"
end

The path were rubygems plugins are to be installed.

See also .platforms= .plugin_suffix_pattern .platforms .plugin_suffix_regexp also in 4.1 · 4.0 · 3.4 · 3.3 · 3.2 · 3.0