[rubygems/rubygems] Pull Gem.win_platform? out of a hot path

`normalize_path` is a pretty hot path, it's called many times per file
in each gem. Since the platform isn't going to change from call to call,
we can conditionally define `normalize_path` based on the value of
`Gem.win_platform?`.

ruby/rubygems@d5e61411f2

Author: tenderlove

lib/rubygems.rb

@@ -16,6 +16,7 @@ module Gem
 require_relative "rubygems/deprecate"
 require_relative "rubygems/errors"
 require_relative "rubygems/target_rbconfig"
+require_relative "rubygems/win_platform"
 
 ##
 # RubyGems is the Ruby standard for publishing and managing third party
@@ -113,18 +114,6 @@ module Gem
 module Gem
   RUBYGEMS_DIR = __dir__
 
-  ##
-  # An Array of Regexps that match windows Ruby platforms.
-
-  WIN_PATTERNS = [
-    /bccwin/i,
-    /cygwin/i,
-    /djgpp/i,
-    /mingw/i,
-    /mswin/i,
-    /wince/i,
-  ].freeze
-
   GEM_DEP_FILES = %w[
     gem.deps.rb
     gems.rb
@@ -160,8 +149,6 @@ module Gem
 
   DEFAULT_SOURCE_DATE_EPOCH = 315_619_200
 
-  @@win_platform = nil
-
   @configuration = nil
   @gemdeps = nil
   @loaded_specs = {}
@@ -1091,18 +1078,6 @@ def self.use_paths(home, *paths)
     self.paths = hash
   end
 
-  ##
-  # Is this a windows platform?
-
-  def self.win_platform?
-    if @@win_platform.nil?
-      ruby_platform = RbConfig::CONFIG["host_os"]
-      @@win_platform = !WIN_PATTERNS.find {|r| ruby_platform =~ r }.nil?
-    end
-
-    @@win_platform
-  end
-
   ##
   # Is this a java platform?
 

lib/rubygems/package.rb

@@ -7,6 +7,7 @@
 
 # rubocop:enable Style/AsciiComments
 
+require_relative "win_platform"
 require_relative "security"
 require_relative "user_interaction"
 
@@ -518,10 +519,12 @@ def install_location(filename, destination_dir) # :nodoc:
     destination
   end
 
-  def normalize_path(pathname)
-    if Gem.win_platform?
+  if Gem.win_platform?
+    def normalize_path(pathname) # :nodoc:
       pathname.downcase
-    else
+    end
+  else
+    def normalize_path(pathname) # :nodoc:
       pathname
     end
   end

lib/rubygems/win_platform.rb

@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+require "rbconfig"
+
+module Gem
+  ##
+  # An Array of Regexps that match windows Ruby platforms.
+
+  WIN_PATTERNS = [
+    /bccwin/i,
+    /cygwin/i,
+    /djgpp/i,
+    /mingw/i,
+    /mswin/i,
+    /wince/i,
+  ].freeze
+
+  @@win_platform = nil
+
+  ##
+  # Is this a windows platform?
+
+  def self.win_platform?
+    if @@win_platform.nil?
+      ruby_platform = RbConfig::CONFIG["host_os"]
+      @@win_platform = !WIN_PATTERNS.find {|r| ruby_platform =~ r }.nil?
+    end
+
+    @@win_platform
+  end
+end