tree 907a350737554d2688ba0b216766ab28096e4b4e
parent 0125ebc5c3f276ac58a5adf1617a6c1141c0fdb3
author Rahul Ravikumar <rahulrav@google.com> 1572833470 +0530
committer Rahul Ravikumar <rahulrav@google.com> 1572833470 +0530

Empty WorkContinuation node makes subsequent nodes the head node and replaces the chain.

* Enqueue runnable looks for a node with no pre-requisites to start a REPLACE
* When we insert an empty node in the middle of the chain, the next node
  becomes the new head node, and previously inserted nodes are replaced.
* This fix just treats a then(emptyList) a no-op and returns the existing
  WorkContinuation.

Fixes: b/142835274
Test: Added unit tests. Ran integration tests.
Change-Id: Ib34badf0477771eb06a6bfe68c7d9f4ed664563b