Modified: MacRuby/trunk/lib/rubygems/installer.rb (4488 => 4489)

--- MacRuby/trunk/lib/rubygems/installer.rb	2010-09-01 23:21:37 UTC (rev 4488)
+++ MacRuby/trunk/lib/rubygems/installer.rb	2010-09-02 02:16:14 UTC (rev 4489)
@@ -37,6 +37,7 @@
   # Raised when there is an error while building extensions.
   #
   class ExtensionBuildError < Gem::InstallError; end
+  class GenerateBinaryError < Gem::InstallError; end
 
   include Gem::UserInteraction
 
@@ -321,20 +322,36 @@
 
     # HACK some gems don't have #! in their executables, restore 2008/06
     #if File.read(exec_path, 2) == '#!' then
-      FileUtils.rm_f bin_script_path # prior install may have been --no-wrappers
+      # FileUtils.rm_f bin_script_path # prior install may have been --no-wrappers
 
-      File.open bin_script_path, 'w', 0755 do |file|
+      bin_script_exists = File.exists?(bin_script_path)
+      new_shebang = shebang(filename)
+      File.open bin_script_path, 'r+', 0755 do |file|
+        if bin_script_exists
+          # If the first line is different than the shebang we want to insert
+          # we are probably overwriting a script installed by another ruby
+          # implementation / version
+          if file.readline.chomp != new_shebang
+            warn = <<-WARN_MESSAGE
+You are installing a new version of #{bin_script_path}.
+This file already exists with a different shebang, possibly from a different
+ruby implementation or version. This operation may break the script.
+WARN_MESSAGE
+            alert_warning(warn)
+            if not ask_yes_no("Do you still wish to continue?")
+              raise GenerateBinaryError, "Could not write #{bin_script_path}"
+            end
+            say "Overwrote #{bin_script_path}" if Gem.configuration.really_verbose
+          end
+          file.seek(0)
+          file.truncate(0)
+        end
         file.print app_script_text(filename)
       end
 
       say bin_script_path if Gem.configuration.really_verbose
 
       generate_windows_script bindir, filename
-    #else
-    #  FileUtils.rm_f bin_script_path
-    #  FileUtils.cp exec_path, bin_script_path,
-    #               :verbose => Gem.configuration.really_verbose
-    #end
   end
 
   ##