Added Kernel#silence_stderr to silence stderr for the duration of the…

… given block. Changed Kernel#` to print a message to stderr (like Unix) instead of raising Errno::ENOENT on Win32.

git-svn-id: http://svn-commit.rubyonrails.org/rails/trunk@2899 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

activesupport/CHANGELOG

@@ -1,5 +1,9 @@
 *SVN*
 
+* Added Kernel#silence_stderr to silence stderr for the duration of the given block [Sam Stephenson]
+
+* Changed Kernel#` to print a message to stderr (like Unix) instead of raising Errno::ENOENT on Win32 [Sam Stephenson]
+
 * Changed 0.blank? to false rather than true since it violates everyone's expectation of blankness.  #2518, #2705 [rails@jeffcole.net]
 
 * When loading classes using const_missing, raise a NameError if and only if the file we tried to load was not present. [Nicholas Seckar]

activesupport/lib/active_support/core_ext/kernel.rb

@@ -29,6 +29,32 @@ def silence_warnings
     $VERBOSE = old_verbose
   end
 
+  # Silences stderr for the duration of the block.
+  #
+  #   silence_stderr do
+  #     $stderr.puts 'This will never be seen'
+  #   end
+  #
+  #   $stderr.puts 'But this will'
+  def silence_stderr
+    old_stderr = STDERR.dup
+    STDERR.reopen(RUBY_PLATFORM =~ /mswin/ ? 'NUL:' : '/dev/null')
+    STDERR.sync = true
+    yield
+  ensure
+    STDERR.reopen(old_stderr)
+  end
+
+  # Makes backticks behave (somewhat more) similarly on all platforms.
+  # On win32 `nonexistent_command` raises Errno::ENOENT; on Unix, the
+  # spawned shell prints a message to stderr and sets $?.  We emulate
+  # Unix on the former but not the latter.
+  def `(command) #:nodoc:
+    super
+  rescue Errno::ENOENT => e
+    STDERR.puts "#$0: #{e}"
+  end
+
   # Method that requires a library, ensuring that rubygems is loaded
   def require_library_or_gem(library_name)
     begin

activesupport/test/core_ext/kernel_test.rb

@@ -20,4 +20,14 @@ def test_silence_warnings_verbose_invariant
   def test_silence_warnings_with_return_value
     assert_equal 1, silence_warnings { 1 }
   end
+
+  def test_silence_stderr
+    old_stderr_position = STDERR.tell
+    silence_stderr { STDERR.puts 'hello world' }
+    assert_equal old_stderr_position, STDERR.tell
+  end
+
+  def test_silence_stderr_with_return_value
+    assert_equal 1, silence_stderr { 1 }
+  end
 end