Add: Ability To Access Progress Bar Instance Using Enumerator Refinement

Why This Change Is Necessary
========================================================================

Without access to the progress bar instance, when using the refinement
there's a lack of ability to do things like log or modify the title
mid-progress like you can with the standard progress bar usage.

What These Changes Do To Address the Issue
========================================================================

If you pass a second argument to the block passed to `with_progressbar`,
the second argument will be the progress bar instance.

Side Effects Caused By This Change
========================================================================

None expected.

------------------------------------------------------------------------

**Relevant URLs:**

  * [Current Ticket Link][1]
  * [Original Ticket Link][2]

**Actions:**

  * Closes 184
  * Closes 185

------------------------------------------------------------------------

[1]: #185
[2]: #184

Author: jfelchner

lib/ruby-progressbar/refinements/enumerator.rb

@@ -1,22 +1,28 @@
 class  ProgressBar
 module Refinements
 module Enumerator
-refine ::Enumerator do
-  def with_progressbar(options = {}, &block)
-    progress_bar = ProgressBar.create(options.merge(:starting_at => 0, :total => size))
+  ARITY_ERROR_MESSAGE = 'Only two arguments allowed to be passed to ' \
+                        'with_progressbar (item, progress_bar)'.freeze
 
-    each do |item|
-      progress_bar.increment
+  refine ::Enumerator do
+    def with_progressbar(options = {}, &block)
+      progress_bar = ProgressBar.create(options.merge(:starting_at => 0, :total => size))
 
-      next unless block
+      each do |item|
+        progress_bar.increment
 
-      yielded_args = []
-      yielded_args << item
+        next unless block
 
-      yield(*yielded_args)
+        yielded_args = []
+        yielded_args << item         if block.arity > 0
+        yielded_args << progress_bar if block.arity > 1
+
+        fail ::ArgumentError, ARITY_ERROR_MESSAGE if block.arity > 2
+
+        yield(*yielded_args)
+      end
     end
   end
 end
 end
 end
-end

spec/lib/ruby-progressbar/refinements/enumerator_spec.rb

@@ -84,6 +84,16 @@ module   Refinements
 
     expect(enumerator.map(&transform)).to eql((0...10).map(&transform))
   end
+
+  it 'passes the progressbar instance to the block when two arguments are requested for the block' do
+    progress     = 0
+    current_item = -1
+
+    (0...10).each.with_progressbar do |item, progress_bar|
+      expect(progress_bar.progress).to be(progress += 1)
+      expect(item).to be(current_item += 1)
+    end
+  end
 end
 end
 end