MVar#take accepts a block as parameter

Author: lionelperrin

lib/concurrent/mvar.rb

@@ -68,10 +68,14 @@ def take(timeout = nil)
 
         # If we timed out we'll still be empty
         if unlocked_full?
-          value = @value
-          @value = EMPTY
-          @empty_condition.signal
-          apply_deref_options(value)
+          if block_given?
+            yield @value
+          else
+            value = @value
+            @value = EMPTY
+            @empty_condition.signal
+            apply_deref_options(value)
+          end
         else
           TIMEOUT
         end

spec/concurrent/mvar_spec.rb

@@ -68,6 +68,28 @@ def dereferenceable_subject(value, opts = {})
         expect(m.take(0.1)).to eq MVar::TIMEOUT
       end
 
+      context 'when a block is given' do
+        it 'yields current value to the block and puts back value' do
+          m = MVar.new(14)
+          expect { |b| m.take(&b) }.to yield_with_args(14)
+          expect(m.take).to eq(14)
+        end
+        it 'puts back value even if an exception is raised' do
+          m = MVar.new(14)
+          expect { m.take { fail 'boom!' } }.to raise_error('boom!')
+          expect(m.take).to eq(14)
+        end
+        it 'returns the returned value of the block' do
+          m = MVar.new(14)
+          expect(m.take{2}).to eq(2)
+          expect(m.take).to eq(14)
+        end
+        it 'returns TIMEOUT on timeout on an empty MVar' do
+          m = MVar.new
+          expect(m.take(0.1){}).to eq MVar::TIMEOUT
+        end
+      end
+
     end
 
     describe '#put' do