1 files changed, 27 insertions, 1 deletions
diff --git a/lib/rubygems/installer.rb b/lib/rubygems/installer.rb
index ae699a90a0..5e2e8e0f42 100644
--- a/lib/rubygems/installer.rb
+++ b/lib/rubygems/installer.rb
@@ -85,6 +85,32 @@ class Gem::Installer
       raise Gem::InstallError, "invalid gem format for #{@gem}"
     end
 
+    if not File.writable? @gem_home or
+        # TODO: Shouldn't have to test for existence of bindir; tests need it.
+        (@gem_home.to_s == Gem.dir and File.exist? Gem.bindir and 
+         not File.writable? Gem.bindir)
+      if options[:user_install] == false # You explicitly don't want to use ~
+        raise Gem::FilePermissionError, @gem_home
+      elsif options[:user_install].nil?
+        say "Warning: falling back to user-level install since #{@gem_home} and #{@bin_dir} aren't both writable."
+      end
+      options[:user_install] = true
+    end
+
+    if options[:user_install]
+      @gem_home = File.join(ENV['HOME'], '.gem')
+
+      user_bin_dir = File.join(@gem_home, 'gems', 'bin')
+      if !ENV['PATH'].split(':').include?(user_bin_dir)
+        say "You don't have #{user_bin_dir} in your PATH."
+        say "You won't be able to run gem-installed executables until you add it."
+      end
+      
+      Dir.mkdir @gem_home if ! File.directory? @gem_home
+      # If it's still not writable, you've got issues.
+      raise Gem::FilePermissionError, @gem_home if ! File.writable? @gem_home
+    end
+
     @spec = @format.spec
 
     @gem_dir = File.join(@gem_home, "gems", @spec.full_name).untaint
@@ -132,7 +158,6 @@ class Gem::Installer
     end
 
     FileUtils.mkdir_p @gem_home unless File.directory? @gem_home
-    raise Gem::FilePermissionError, @gem_home unless File.writable? @gem_home
 
     Gem.ensure_gem_subdirectories @gem_home
 
@@ -206,6 +231,7 @@ class Gem::Installer
 
     file_name = File.join @gem_home, 'specifications',
                           "#{@spec.full_name}.gemspec"
+
     file_name.untaint
 
     File.open(file_name, "w") do |file|