From b948b8188dd59c40105f5a9f3a89e98f52b47029 Mon Sep 17 00:00:00 2001
From: Kouhei Sutou <kou@clear-code.com>
Date: Sun, 11 Nov 2012 19:25:05 +0900
Subject: [PATCH] Reject uninstalling a default gem

Note: Gem::Specification#default_gem? is suitable name? Should it be
private?
---
 lib/rubygems/specification.rb                 | 10 +++++++++-
 lib/rubygems/test_case.rb                     |  1 +
 lib/rubygems/uninstaller.rb                   | 16 ++++++++++++++--
 .../test_gem_commands_uninstall_command.rb    | 19 +++++++++++++++++++
 4 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/lib/rubygems/specification.rb b/lib/rubygems/specification.rb
index a3d621d16179..8f6ebe94ee1d 100644
--- a/lib/rubygems/specification.rb
+++ b/lib/rubygems/specification.rb
@@ -612,6 +612,10 @@ def test_files= files
   attr_accessor :specification_version
 
   class << self
+    def default_specifications_dir
+      File.join(Gem.default_dir, "specifications", "default")
+    end
+
     private
     def each_spec(search_dirs) # :nodoc:
       search_dirs.each { |dir|
@@ -625,7 +629,7 @@ def each_spec(search_dirs) # :nodoc:
     end
 
     def each_default(&block) # :nodoc:
-      each_spec([File.join(Gem.default_dir, "specifications", "default")],
+      each_spec([default_specifications_dir],
                 &block)
     end
 
@@ -2508,6 +2512,10 @@ def reset_nil_attributes_to_default
 
       instance_variable_set "@#{attribute}", value
     end
+
+  def default_gem?
+    loaded_from &&
+      File.dirname(loaded_from) == self.class.default_specifications_dir
   end
 
   extend Gem::Deprecate
diff --git a/lib/rubygems/test_case.rb b/lib/rubygems/test_case.rb
index 1bf9c73d6acd..8cf5faf6a185 100644
--- a/lib/rubygems/test_case.rb
+++ b/lib/rubygems/test_case.rb
@@ -516,6 +516,7 @@ def new_spec name, version, deps = nil, *files
 
   def new_default_spec(name, version, deps = nil, *files)
     spec = new_spec(name, version, deps)
+    spec.loaded_from = File.join(@default_spec_dir, spec.spec_name)
     spec.files = files
 
     lib_dir = File.join(@tempdir, "default_gems", "lib")
diff --git a/lib/rubygems/uninstaller.rb b/lib/rubygems/uninstaller.rb
index 9fdcf0e866f9..b1500b07480a 100644
--- a/lib/rubygems/uninstaller.rb
+++ b/lib/rubygems/uninstaller.rb
@@ -74,14 +74,26 @@ def initialize(gem, options = {})
   def uninstall
     list = Gem::Specification.find_all_by_name(@gem, @version)
 
+    default_specs, list = list.partition do |spec|
+      spec.default_gem?
+    end
+
     list, other_repo_specs = list.partition do |spec|
       @gem_home == spec.base_dir or
       (@user_install and spec.base_dir == Gem.user_dir)
     end
 
     if list.empty? then
-      raise Gem::InstallError, "gem #{@gem.inspect} is not installed" if
-        other_repo_specs.empty?
+      if other_repo_specs.empty?
+        if default_specs.empty?
+          raise Gem::InstallError, "gem #{@gem.inspect} is not installed"
+        else
+          message =
+            "gem #{@gem.inspect} cannot be uninstalled " +
+            "because it is a default gem"
+          raise Gem::InstallError, message
+        end
+      end
 
       other_repos = other_repo_specs.map { |spec| spec.base_dir }.uniq
 
diff --git a/test/rubygems/test_gem_commands_uninstall_command.rb b/test/rubygems/test_gem_commands_uninstall_command.rb
index 9a2b615fa267..964ce85cc34b 100644
--- a/test/rubygems/test_gem_commands_uninstall_command.rb
+++ b/test/rubygems/test_gem_commands_uninstall_command.rb
@@ -174,5 +174,24 @@ def test_execute_with_force_ignores_dependencies
     assert Gem::Specification.find_all_by_name('dep_x').length > 0
     assert Gem::Specification.find_all_by_name('x').length == 0
   end
+
+  def test_execute_default_gem
+    default_gem_spec = new_default_spec("default", "2.0.0.0",
+                                        nil, "default/gem.rb")
+    install_default_specs(default_gem_spec)
+
+    ui = Gem::MockGemUi.new
+
+    @cmd.options[:args] = %w[default]
+    @cmd.options[:executables] = true
+
+    use_ui ui do
+      e = assert_raises Gem::InstallError do
+        @cmd.execute
+      end
+      assert_equal "gem \"default\" cannot be uninstalled because it is a default gem",
+                   e.message
+    end
+  end
 end