Return Request context cancelled error (#93)

* request context cancelled error

graphsync.go

@@ -94,6 +94,13 @@ const (
 	RequestCancelled = ResponseStatusCode(35)
 )
 
+// RequestContextCancelledErr is an error message received on the error channel when the request context given by the user is cancelled/times out
+type RequestContextCancelledErr struct{}
+
+func (e RequestContextCancelledErr) Error() string {
+	return "Request Context Cancelled"
+}
+
 // RequestFailedBusyErr is an error message received on the error channel when the peer is busy
 type RequestFailedBusyErr struct{}
 

requestmanager/requestmanager_test.go

@@ -199,8 +199,13 @@ func TestCancelRequestInProgress(t *testing.T) {
 
 	testutil.VerifyEmptyResponse(requestCtx, t, returnedResponseChan1)
 	td.blockChain.VerifyWholeChain(requestCtx, returnedResponseChan2)
-	testutil.VerifyEmptyErrors(requestCtx, t, returnedErrorChan1)
+
 	testutil.VerifyEmptyErrors(requestCtx, t, returnedErrorChan2)
+
+	errors := testutil.CollectErrors(requestCtx, t, returnedErrorChan1)
+	require.Len(t, errors, 1)
+	_, ok := errors[0].(graphsync.RequestContextCancelledErr)
+	require.True(t, ok)
 }
 
 func TestCancelManagerExitsGracefully(t *testing.T) {

requestmanager/responsecollector.go

@@ -80,10 +80,24 @@ func (rc *responseCollector) collectResponses(
 			case <-rc.ctx.Done():
 				return
 			case <-requestCtx.Done():
+				select {
+				case <-rc.ctx.Done():
+				case returnedErrors <- graphsync.RequestContextCancelledErr{}:
+				}
 				return
 			case err, ok := <-incomingErrors:
 				if !ok {
 					incomingErrors = nil
+					// even if the `incomingErrors` channel is closed without any error,
+					// the context could still have timed out in which case we need to inform the caller of the same.
+					select {
+					case <-requestCtx.Done():
+						select {
+						case <-rc.ctx.Done():
+						case returnedErrors <- graphsync.RequestContextCancelledErr{}:
+						}
+					default:
+					}
 				} else {
 					receivedErrors = append(receivedErrors, err)
 				}