[rubygems/rubygems] Only show "Defaulting to user installation" message when it matters.

https://github.com/rubygems/rubygems/commit/61b0947225

lib/rubygems/command.rb

@@ -22,6 +22,15 @@ class Gem::Command
 
   Gem::OptionParser.accept Symbol, &:to_sym
 
+  ##
+  # Names of commands that should print "Defaulting to user installation"
+  # warning.
+
+  COMMANDS_WITH_AUTO_INSTALL_DIR_WARNING = [
+    "install",
+    "update",
+  ].freeze
+
   ##
   # The name of the command.
 
@@ -323,7 +332,8 @@ class Gem::Command
     elsif @when_invoked
       @when_invoked.call options
     else
-      if Gem.paths.auto_user_install && !options[:install_dir] && !options[:user_install]
+      if COMMANDS_WITH_AUTO_INSTALL_DIR_WARNING.include?(@command) && \
+         Gem.paths.auto_user_install && !options[:install_dir] && !options[:user_install]
         self.ui.say "Defaulting to user installation because default installation directory (#{Gem.default_dir}) is not writable."
       end
 

test/rubygems/test_gem_command.rb

@@ -399,4 +399,66 @@ ERROR:  Possible alternatives: non_existent_with_hint
 
     assert_equal expected, @ui.error
   end
+
+  def test_show_defaulting_to_user_install_when_appropriate
+    omit "this test doesn't work with ruby-core setup" if ruby_repo?
+
+    Gem.stub(:default_dir, "/this-directory-does-not-exist") do
+      # Replace `Gem.paths` with a new instance, so `Gem.paths.auto_user_install`
+      # is accurate.
+      Gem.stub(:paths, Gem::PathSupport.new(ENV)) do
+        output_regex = "Defaulting to user installation"
+
+        test_command = Class.new(Gem::Command) do
+          def initialize
+            # "gem install" should ALWAYS print the warning.
+            super("install", "Gem::Command instance for testing")
+          end
+
+          def execute
+            true
+          end
+        end
+
+        cmd = test_command.new
+
+        use_ui @ui do
+          cmd.invoke
+          assert_match output_regex, @ui.output,
+            "Gem.default_dir = #{Gem.default_dir.inspect}\n" \
+            "Gem.paths.auto_user_install = #{Gem.paths.auto_user_install.inspect}"
+        end
+      end
+    end
+  end
+
+  def test_dont_show_defaulting_to_user_install_when_appropriate
+    Gem.stub(:default_dir, "/this-directory-does-not-exist") do
+      # Replace `Gem.paths` with a new instance, so `Gem.paths.auto_user_install`
+      # is accurate.
+      Gem.stub(:paths, Gem::PathSupport.new(ENV)) do
+        output_regex = /^Defaulting to user installation/
+
+        test_command = Class.new(Gem::Command) do
+          def initialize
+            # "gem blargh" should NEVER print the warning.
+            super("blargh", "Gem::Command instance for testing")
+          end
+
+          def execute
+            true
+          end
+        end
+
+        cmd = test_command.new
+
+        use_ui @ui do
+          cmd.invoke
+          assert_no_match output_regex, @ui.output,
+            "Gem.default_dir = #{Gem.default_dir.inspect}\n" \
+            "Gem.paths.auto_user_install = #{Gem.paths.auto_user_install.inspect}"
+        end
+      end
+    end
+  end
 end