From 4edfee431ef3fdc3a95b2dc9c8ff5322c9b480a3 Mon Sep 17 00:00:00 2001
From: Gonzalo <grzuy0@gmail.com>
Date: Wed, 7 Feb 2018 14:18:14 -0300
Subject: [PATCH] Make dry-run smart about potential file task executions.
 Fixes #92

---
 lib/rake/file_task.rb        |  4 ++++
 lib/rake/task.rb             | 11 ++++++++++-
 test/test_rake_functional.rb | 23 +++++++++++++++++++++++
 3 files changed, 37 insertions(+), 1 deletion(-)

diff --git a/lib/rake/file_task.rb b/lib/rake/file_task.rb
index 3130b5cfc..48c52c470 100644
--- a/lib/rake/file_task.rb
+++ b/lib/rake/file_task.rb
@@ -17,6 +17,10 @@ def needed?
       ! File.exist?(name) || out_of_date?(timestamp) || @application.options.build_all
     end
 
+    def potentially_needed?
+      needed? || prerequisite_tasks.any?(&:potentially_needed?)
+    end
+
     # Time stamp for file task.
     def timestamp
       if File.exist?(name)
diff --git a/lib/rake/task.rb b/lib/rake/task.rb
index 256571112..4b4061c72 100644
--- a/lib/rake/task.rb
+++ b/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 && potentially_needed?
+          application.trace "** May execute (dry run) #{name}"
+        end
       end
     rescue Exception => ex
       add_chain_to(ex, new_chain)
@@ -200,6 +205,10 @@ def invoke_with_call_chain(task_args, invocation_chain) # :nodoc:
     end
     protected :invoke_with_call_chain
 
+    def potentially_needed?
+      needed?
+    end
+
     def add_chain_to(exception, new_chain) # :nodoc:
       exception.extend(InvocationExceptionMixin) unless
         exception.respond_to?(:chain)
diff --git a/test/test_rake_functional.rb b/test/test_rake_functional.rb
index 33d4dc0b2..fb3886ac8 100644
--- a/test/test_rake_functional.rb
+++ b/test/test_rake_functional.rb
@@ -243,6 +243,29 @@ def test_dry_run
     refute_match %r{OTHER}, @out
   end
 
+  def test_dry_run_smart_about_potential_file_executions
+    FileUtils.touch("fileA")
+    FileUtils.touch("fileB")
+    FileUtils.touch("fileC")
+    FileUtils.touch("fileD")
+
+    rakefile <<-RAKEFILE
+      file "fileA" do; end
+      file "fileB" => ['fileA'] do; end
+      file "fileC" => ['fileB'] do; end
+      file "fileD" => ['fileC'] do; end
+    RAKEFILE
+
+    sleep 1
+    FileUtils.touch("fileA")
+
+    rake "-n", "fileD"
+
+    assert_match(/Execute \(dry run\) fileB/, @err)
+    assert_match(/May execute \(dry run\) fileC/, @err)
+    assert_match(/May execute \(dry run\) fileD/, @err)
+  end
+
   # Test for the trace/dry_run bug found by Brian Chandler
   def test_dry_run_bug
     rakefile_dryrun