NpeFix generates an impossible patch, `return null` in a constructor

[monperrus]

Good news, we have a patch in repairnator!

+++ /StreamDefinitionController.java
@@ -379,2 +379,5 @@

+           if (StreamDefinitionController.this.streamService == null) {
+               return null;
+           }
            streamDeploymentStates = StreamDefinitionController.this.streamService

But this patch is impossible, because it is in a constructor, and return null is impossible in a constructor.

[tdurieux]

it is probably an error in the patch generator. I need more info, the complete json result will be useful

[surli]

It's not formatted at all, but here it is: https://github.com/Spirals-Team/librepair-experiments/blob/spring-cloud-spring-cloud-dataflow-284933348-20171008-064257_bugonly/repairnator.npefix.results

[tdurieux]

NPEFix does not generate correctly the patch. The strategy is a return VOID in a constructor, it means that it has to wrap with an if not null the end of the constructor.

Like this:

+++ /StreamDefinitionController.java
@@ -379,2 +379,5 @@

+           if (StreamDefinitionController.this.streamService != null) {
+               streamDeploymentStates = StreamDefinitionController.this.streamService
+           }
-           streamDeploymentStates = StreamDefinitionController.this.streamService

[monperrus]

This is impossible in this case, the compiler complains because because the field streamDeploymentStates may be uninitialized.

[tdurieux]

True, I forgot that we remove final modifier...

+++ /StreamDefinitionController.java
@@ -379,2 +379,5 @@

+           if (StreamDefinitionController.this.streamService != null) {
+               streamDeploymentStates = StreamDefinitionController.this.streamService
+           } else {
+               streamDeploymentStates = null;
+           }
-           streamDeploymentStates = StreamDefinitionController.this.streamService