Support separate live stream for stderr

4 files changed, 102 insertions, 8 deletions

diff --git a/lib/mixlib/shellout.rb b/lib/mixlib/shellout.rb
index e446448..a633819 100644
--- a/lib/mixlib/shellout.rb
+++ b/lib/mixlib/shellout.rb
@@ -54,10 +54,13 @@ module Mixlib
     attr_accessor :valid_exit_codes
 
     # When live_stream is set, stdout and stderr of the subprocess will be
-    # copied to it as the subprocess is running. For example, if live_stream is
-    # set to STDOUT, the command's output will be echoed to STDOUT.
+    # copied to it as the subprocess is running. The stderr will also be copied,
+    # unless live_stderr_stream is set to nil or a different object. For example,
+    # if live_stream is set to STDOUT, the command's output will be echoed to STDOUT.
     attr_accessor :live_stream
 
+    attr_writer :live_stderr_stream
+
     # ShellOut will push data from :input down the stdin of the subprocss.
     # Normally set via options passed to new.
     # Default: nil
@@ -163,6 +166,20 @@ module Mixlib
       @command = command_args.size == 1 ? command_args.first : command_args
     end
 
+    # When live_stderr_stream is set, the stderr of the subprocess will be
+    # copied to it as the subprocess is running. For example, if live_stderr_stream is
+    # set to STDERR, the command's output will be echoed to STDERR. The default
+    # value is to match live_stream, so setting live_stream to STDOUT will also
+    # set live_stderr_stream to STDOUT. If you only want the stdout of the subprocess
+    # copied, then you should explicitly set live_stderr_stream to nil.
+    def live_stderr_stream
+      # We can't use ||= because it would override an explicit nil
+      unless defined?(@live_stderr_stream)
+        @live_stderr_stream = live_stream
+      end
+      @live_stderr_stream
+    end
+
     # Set the umask that the subprocess will have. If given as a string, it
     # will be converted to an integer by String#oct.
     def umask=(new_umask)
@@ -287,6 +304,9 @@ module Mixlib
           self.valid_exit_codes = Array(setting)
         when 'live_stream'
           self.live_stream = setting
+        when 'live_stderr_stream'
+          puts "Setting to #{setting}"
+          self.live_stderr_stream = setting
         when 'input'
           self.input = setting
         when 'logger'
diff --git a/lib/mixlib/shellout/unix.rb b/lib/mixlib/shellout/unix.rb
index 46c2c73..249c3d4 100644
--- a/lib/mixlib/shellout/unix.rb
+++ b/lib/mixlib/shellout/unix.rb
@@ -288,7 +288,7 @@ module Mixlib
       def read_stderr_to_buffer
         while chunk = child_stderr.read_nonblock(READ_SIZE)
           @stderr << chunk
-          @live_stream << chunk if @live_stream
+          live_stderr_stream << chunk if live_stderr_stream
         end
       rescue Errno::EAGAIN
       rescue EOFError
diff --git a/lib/mixlib/shellout/windows.rb b/lib/mixlib/shellout/windows.rb
index 832584a..62adc37 100644
--- a/lib/mixlib/shellout/windows.rb
+++ b/lib/mixlib/shellout/windows.rb
@@ -167,7 +167,7 @@ module Mixlib
           begin
             next_chunk = stderr_read.readpartial(READ_SIZE)
             @stderr << next_chunk
-            @live_stream << next_chunk if @live_stream
+            @live_stderr_stream << next_chunk if @live_stderr_stream
           rescue EOFError
             stderr_read.close
             open_streams.delete(stderr_read)
diff --git a/spec/mixlib/shellout_spec.rb b/spec/mixlib/shellout_spec.rb
index 5dcb6a7..72d550e 100644
--- a/spec/mixlib/shellout_spec.rb
+++ b/spec/mixlib/shellout_spec.rb
@@ -187,8 +187,56 @@ describe Mixlib::ShellOut do
         let(:value) { stream }
         let(:stream) { StringIO.new }
 
+        before(:each) do
+          shell_cmd.live_stream = stream
+        end
+
         it "should set the live stream" do
-          should eql(value)
+          shell_cmd.live_stream.should eql(stream)
+        end
+
+        it "should set the live stderr stream" do
+          shell_cmd.live_stderr_stream.should eql(stream)
+        end
+      end
+
+      context 'when setting a live stream and live stderr stream separately' do
+        let(:accessor) { :live_stream }
+        let(:stream) { StringIO.new }
+        let(:value) { stream }
+        let(:stdout_stream) { StringIO.new }
+        let(:stderr_stream) { StringIO.new }
+
+        before(:each) do
+          shell_cmd.live_stream = stdout_stream
+          shell_cmd.live_stderr_stream = stderr_stream
+        end
+
+        it "should set the live stream" do
+          shell_cmd.live_stream.should eql(stdout_stream)
+        end
+
+        it "should set the live stream" do
+          shell_cmd.live_stderr_stream.should eql(stderr_stream)
+        end
+      end
+
+      context 'when setting a live stream and explicitly disabling live stderr stream' do
+        let(:accessor) { :live_stream }
+        let(:value) { stream }
+        let(:stream) { StringIO.new }
+
+        before(:each) do
+          shell_cmd.live_stream = stream
+          shell_cmd.live_stderr_stream = nil
+        end
+
+        it "should set the live stream" do
+          shell_cmd.live_stream.should eql(stream)
+        end
+
+        it "should set the live stderr stream" do
+          shell_cmd.live_stderr_stream.should eql(nil)
         end
       end
 
@@ -457,9 +505,35 @@ describe Mixlib::ShellOut do
         stream.string.should include("hello#{LINE_ENDING}")
       end
 
-      it "should copy the child's stderr to the live stream" do
-        shell_cmd.run_command
-        stream.string.should include("world#{LINE_ENDING}")
+      context "with default stderr stream" do
+        it "should copy the child's stderr to the live stream" do
+          shell_cmd.run_command
+          stream.string.should include("world#{LINE_ENDING}")
+        end
+      end
+
+      context "without an stderr stream" do
+        it "should not copy the child's stderr to the live stream" do
+          shell_cmd.live_stderr_stream = nil
+          shell_cmd.run_command
+          stream.string.should_not include("world#{LINE_ENDING}")
+        end
+      end
+
+      context "with a separate stderr stream" do
+        let(:stderr_stream) { StringIO.new }
+
+        it "should not copy the child's stderr to the live stream" do
+          shell_cmd.live_stderr_stream = stderr_stream
+          shell_cmd.run_command
+          stream.string.should_not include("world#{LINE_ENDING}")
+        end
+
+        it "should copy the child's stderr to the live stderr stream" do
+          shell_cmd.live_stderr_stream = stderr_stream
+          shell_cmd.run_command
+          stderr_stream.string.should include("world#{LINE_ENDING}")
+        end
       end
     end