Print a warning if a task is skipped because of re-invocation. Resolves #1689

CHANGELOG.md

@@ -6,6 +6,7 @@ Reverse Chronological Order:
 
 https://github.com/capistrano/capistrano/compare/v3.5.0...HEAD
 
+  * Added warning about future deprecation of reinvocation behaviour (@troelskn)
   * Added a `doctor:servers` subtask that outputs a summary of servers, roles & properties (@irvingwashington)
   * Raise a better error when an ‘after’ hook isn’t found (@jdelStrother)
   * Restrict the uploaded git wrapper script permissions to 700 (@irvingwashington)

lib/capistrano/dsl.rb

@@ -11,8 +11,18 @@ module Capistrano
     include Paths
     include Stages
 
-    def invoke(task, *args)
-      Rake::Task[task].invoke(*args)
+    def invoke(task_name, *args)
+      task = Rake::Task[task_name]
+      if task && task.already_invoked
+        file, line, = caller.first.split(":")
+        colors = SSHKit::Color.new($stderr)
+        $stderr.puts colors.colorize("Skipping task `#{task_name}'.", :yellow)
+        $stderr.puts "Capistrano tasks may only be invoked once. Since task `#{task}' was previously invoked, invoke(\"#{task_name}\") at #{file}:#{line} will be skipped."
+        $stderr.puts "If you really meant to run this task again, first call Rake::Task[\"#{task_name}\"].reenable"
+        $stderr.puts colors.colorize("THIS BEHAVIOR MAY CHANGE IN A FUTURE VERSION OF CAPISTRANO. Please join the conversation here if this affects you.", :red)
+        $stderr.puts colors.colorize("https://github.com/capistrano/capistrano/issues/1686", :red)
+      end
+      task.invoke(*args)
     end
 
     def t(key, options={})

spec/lib/capistrano/dsl_spec.rb

@@ -69,5 +69,16 @@ module Capistrano
         end
       end
     end
+
+    describe "#invoke" do
+      it "will print a message on stderr, when reinvoking task" do
+        Rake::Task.define_task("some_task")
+
+        dsl.invoke("some_task")
+        expect do
+          dsl.invoke("some_task")
+        end.to output(/.*Capistrano tasks may only be invoked once.*/).to_stderr
+      end
+    end
   end
 end