Don't run file tasks needlessly. Fixes ruby#246

Author: grzuy

lib/rake/file_task.rb

@@ -30,14 +30,7 @@ def timestamp
 
     # Are there any prerequisites with a later time than the given time stamp?
     def out_of_date?(stamp)
-      all_prerequisite_tasks.any? { |prereq|
-        prereq_task = application[prereq, @scope]
-        if prereq_task.instance_of?(Rake::FileTask)
-          prereq_task.timestamp > stamp || @application.options.build_all
-        else
-          prereq_task.timestamp > stamp
-        end
-      }
+      prerequisite_tasks.any? { |task| task.timestamp > stamp }
     end
 
     # ----------------------------------------------------------------

lib/rake/task.rb

@@ -192,7 +192,12 @@ def invoke_with_call_chain(task_args, invocation_chain) # :nodoc:
         return if @already_invoked
         @already_invoked = true
         invoke_prerequisites(task_args, new_chain)
-        execute(task_args) if needed?
+
+        if needed?
+          execute(task_args)
+        elsif application.options.dryrun && prerequisite_tasks.any? { |p| p.is_a?(Rake::FileTask) }
+          application.trace "** Execute (dry run) #{name}"
+        end
       end
     rescue Exception => ex
       add_chain_to(ex, new_chain)

test/test_rake_functional.rb

@@ -304,6 +304,25 @@ def dryrun_tasks
     }
   end
 
+  def test_file_timestamps_respected_despite_task_prerequisite
+    rakefile <<-RAKEFILE
+      task "some_task" do
+      end
+
+      file "A" => "some_task"
+      file "B" => "A" do |t|
+        touch t.name
+      end
+    RAKEFILE
+
+    FileUtils.touch("A")
+    FileUtils.touch("B")
+
+    rake "B"
+
+    assert(@err !~ /touch B/)
+  end
+
   def test_update_midway_through_chaining_to_file_task
     rakefile_file_chains