1 files changed, 85 insertions, 0 deletions
diff --git a/lib/rubygems/path_support.rb b/lib/rubygems/path_support.rb
new file mode 100644
index 0000000000..13091e29ba
--- /dev/null
+++ b/lib/rubygems/path_support.rb
@@ -0,0 +1,85 @@
+# frozen_string_literal: true
+
+##
+#
+# Gem::PathSupport facilitates the GEM_HOME and GEM_PATH environment settings
+# to the rest of RubyGems.
+#
+class Gem::PathSupport
+  ##
+  # The default system path for managing Gems.
+  attr_reader :home
+
+  ##
+  # Array of paths to search for Gems.
+  attr_reader :path
+
+  ##
+  # Directory with spec cache
+  attr_reader :spec_cache_dir # :nodoc:
+
+  ##
+  #
+  # Constructor. Takes a single argument which is to be treated like a
+  # hashtable, or defaults to ENV, the system environment.
+  #
+  def initialize(env)
+    @home = normalize_home_dir(env["GEM_HOME"] || Gem.default_dir)
+    @path = split_gem_path env["GEM_PATH"], @home
+
+    @spec_cache_dir = env["GEM_SPEC_CACHE"] || Gem.default_spec_cache_dir
+  end
+
+  private
+
+  def normalize_home_dir(home)
+    if File::ALT_SEPARATOR
+      home = home.gsub(File::ALT_SEPARATOR, File::SEPARATOR)
+    end
+
+    expand(home)
+  end
+
+  ##
+  # Split the Gem search path (as reported by Gem.path).
+
+  def split_gem_path(gpaths, home)
+    # FIX: it should be [home, *path], not [*path, home]
+
+    gem_path = []
+
+    if gpaths
+      gem_path = gpaths.split(Gem.path_separator)
+      # Handle the path_separator being set to a regexp, which will cause
+      # end_with? to error
+      if /#{Gem.path_separator}\z/.match?(gpaths)
+        gem_path += default_path
+      end
+
+      if File::ALT_SEPARATOR
+        gem_path.map! do |this_path|
+          this_path.gsub File::ALT_SEPARATOR, File::SEPARATOR
+        end
+      end
+
+      gem_path << home
+    else
+      gem_path = default_path
+    end
+
+    gem_path.map {|path| expand(path) }.uniq
+  end
+
+  # Return the default Gem path
+  def default_path
+    Gem.default_path + [@home]
+  end
+
+  def expand(path)
+    if File.directory?(path)
+      File.realpath(path)
+    else
+      path
+    end
+  end
+end