Added IVar#set? to unify Channel::Probe.

Author: jdantonio

lib/concurrent/ivar.rb

@@ -127,6 +127,13 @@ def fail(reason = StandardError.new)
       set { raise reason }
     end
 
+    def set?(value = NO_VALUE, &block)
+      set(value, &block)
+      true
+    rescue MultipleAssignmentError
+      false
+    end
+
     protected
 
     # @!visibility private

spec/concurrent/ivar_shared.rb

@@ -93,4 +93,66 @@
       expect(subject.fail).to eq subject
     end
   end
+
+  describe '#set?' do
+
+    context 'when unset' do
+
+      it 'assigns the value' do
+        subject.set?(32)
+        expect(subject.value).to eq 32
+      end
+
+      it 'assigns the block result' do
+        subject.set?{ 32 }
+        expect(subject.value).to eq 32
+      end
+
+      it 'returns true' do
+        expect(subject.set?('hi')).to eq true
+      end
+    end
+
+    context 'when fulfilled' do
+
+      before(:each) { subject.set(27) }
+
+      it 'does not assign the value' do
+        subject.set?(88)
+        expect(subject.value).to eq 27
+      end
+
+      it 'does not assign the block result' do
+        subject.set?{ 88 }
+        expect(subject.value).to eq 27
+      end
+
+      it 'returns false' do
+        expect(subject.set?('hello')).to eq false
+      end
+    end
+
+    context 'when rejected' do
+
+      before(:each) { subject.fail }
+
+      it 'does not assign the value' do
+        subject.set?(88)
+        expect(subject).to be_rejected
+      end
+
+      it 'does not assign the block result' do
+        subject.set?{ 88 }
+        expect(subject).to be_rejected
+      end
+
+      it 'has a nil value' do
+        expect(subject.value).to be_nil
+      end
+
+      it 'returns false' do
+        expect(subject.set?('hello')).to eq false
+      end
+    end
+  end
 end