Move trace heavy lifting to its own module.

lib/rake.rb

@@ -43,6 +43,7 @@
 require 'rake/task_argument_error'
 require 'rake/rule_recursion_overflow_error'
 require 'rake/rake_module'
+require 'rake/trace_output'
 require 'rake/pseudo_status'
 require 'rake/task_arguments'
 require 'rake/invocation_chain'

lib/rake/application.rb

@@ -5,6 +5,7 @@
 require 'rake/file_list'
 require 'rake/thread_pool'
 require 'rake/thread_history_display'
+require 'rake/trace_output'
 require 'rake/win32'
 
 module Rake
@@ -17,6 +18,7 @@ module Rake
   #
   class Application
     include TaskManager
+    include TraceOutput
 
     # The name of the application (typically 'rake')
     attr_reader :name
@@ -316,13 +318,7 @@ def display_prerequisites
 
     def trace(*strings)
       options.trace_output ||= $stderr
-      sep = $\ || "\n"
-      if strings.empty?
-        output = sep
-      else
-        output = strings.map { |s| s.end_with?(sep) ? s : s + sep }.join
-      end
-      options.trace_output.print(output)
+      trace_on(options.trace_output, *strings)
     end
 
     def sort_options(options)

lib/rake/trace_output.rb

@@ -0,0 +1,19 @@
+module Rake
+  module TraceOutput
+
+    # Write trace output to output stream +out+.
+    #
+    # The write is done as a single IO call (to print) to lessen the
+    # chance that the trace output is interrupted by other tasks also
+    # producing output.
+    def trace_on(out, *strings)
+      sep = $\ || "\n"
+      if strings.empty?
+        output = sep
+      else
+        output = strings.map { |s| s.end_with?(sep) ? s : s + sep }.join
+      end
+      out.print(output)
+    end
+  end
+end

test/test_rake_application.rb

@@ -1,5 +1,4 @@
 require File.expand_path('../helper', __FILE__)
-require 'stringio'
 
 class TestRakeApplication < Rake::TestCase
 
@@ -341,46 +340,6 @@ def test_handle_options_trace_does_not_eat_following_task_names
     assert @app.options.trace
   end
 
-  class PrintSpy
-    attr_reader :result, :calls
-    def initialize
-      @result = ""
-      @calls = 0
-    end
-    def print(string)
-      @result << string
-      @calls += 1
-    end
-  end
-
-  def test_trace_issues_single_io_for_args_with_empty_args
-    spy = PrintSpy.new
-    @app.options.trace_output = spy
-    @app.trace
-    assert_equal "\n", spy.result
-    assert_equal 1, spy.calls
-  end
-
-  def test_trace_issues_single_io_for_args_multiple_strings
-    spy = PrintSpy.new
-    @app.options.trace_output = spy
-    @app.trace("HI\n", "LO")
-    assert_equal "HI\nLO\n", spy.result
-    assert_equal 1, spy.calls
-  end
-
-  def test_trace_issues_single_io_for_args_multiple_strings_and_alternate_sep
-    old_sep = $\
-    $\ = "\r"
-    spy = PrintSpy.new
-    @app.options.trace_output = spy
-    @app.trace("HI\r", "LO")
-    assert_equal "HI\rLO\r", spy.result
-    assert_equal 1, spy.calls
-  ensure
-    $\ = old_sep
-  end
-
   def test_good_run
     ran = false
 

test/test_trace_output.rb

@@ -0,0 +1,43 @@
+require File.expand_path('../helper', __FILE__)
+require 'stringio'
+
+class TestTraceOutput < Rake::TestCase
+  include Rake::TraceOutput
+
+  class PrintSpy
+    attr_reader :result, :calls
+    def initialize
+      @result = ""
+      @calls = 0
+    end
+    def print(string)
+      @result << string
+      @calls += 1
+    end
+  end
+
+  def test_trace_issues_single_io_for_args_with_empty_args
+    spy = PrintSpy.new
+    trace_on(spy)
+    assert_equal "\n", spy.result
+    assert_equal 1, spy.calls
+  end
+
+  def test_trace_issues_single_io_for_args_multiple_strings
+    spy = PrintSpy.new
+    trace_on(spy, "HI\n", "LO")
+    assert_equal "HI\nLO\n", spy.result
+    assert_equal 1, spy.calls
+  end
+
+  def test_trace_issues_single_io_for_args_multiple_strings_and_alternate_sep
+    old_sep = $\
+    $\ = "\r"
+    spy = PrintSpy.new
+    trace_on(spy, "HI\r", "LO")
+    assert_equal "HI\rLO\r", spy.result
+    assert_equal 1, spy.calls
+  ensure
+    $\ = old_sep
+  end
+end