Merge pull request moby#2385 from venturehacks/panic_failed_to_get_edge

don't cast Value when pipe is errored

solver/edge.go

@@ -458,7 +458,14 @@ func (e *edge) processUpdate(upt pipe.Receiver) (depChanged bool) {
 			dep.err = err
 		}
 
-		state := upt.Status().Value.(*edgeState)
+		if upt.Status().Value == nil {
+			return
+		}
+		state, isEdgeState := upt.Status().Value.(*edgeState)
+		if !isEdgeState {
+			bklog.G(context.TODO()).Warnf("invalid edgeState value for update: %T", state)
+			return
+		}
 
 		if len(dep.keys) < len(state.keys) {
 			newKeys := state.keys[len(dep.keys):]

solver/scheduler.go

@@ -352,7 +352,7 @@ func (pf *pipeFactory) NewInputRequest(ee Edge, req *edgeRequest) pipe.Receiver
 	target := pf.s.ef.getEdge(ee)
 	if target == nil {
 		return pf.NewFuncRequest(func(_ context.Context) (interface{}, error) {
-			return req, errors.Errorf("failed to get edge: inconsistent graph state")
+			return nil, errors.Errorf("failed to get edge: inconsistent graph state")
 		})
 	}
 	p := pf.s.newPipe(target, pf.e, pipe.Request{Payload: req})