If a group of deps has only one unique element, store it bare.

Not storing it bare both breaks equality comparison for GroupedList and
uses more space.

--
Change-Id: Iaf4f88908ecf4293cfc31dbd896f46e1da3b4184
Reviewed-on: https://bazel-review.googlesource.com/#/c/6850/
MOS_MIGRATED_REVID=137099785

1 files changed, 4 insertions, 4 deletions

diff --git a/src/main/java/com/google/devtools/build/lib/util/GroupedList.java b/src/main/java/com/google/devtools/build/lib/util/GroupedList.java
index a6f9fbe683..9babacff2b 100644
--- a/src/main/java/com/google/devtools/build/lib/util/GroupedList.java
+++ b/src/main/java/com/google/devtools/build/lib/util/GroupedList.java
@@ -66,12 +66,14 @@ public class GroupedList<T> implements Iterable<Collection<T>> {
     // Iterables.getFirst will return null, and null is not instanceof List.
     Preconditions.checkState(!(Iterables.getFirst(helper.elements, null) instanceof List),
         "Cannot make grouped list of lists: %s", helper);
-    Set<T> uniquifier = CompactHashSet.createWithExpectedSize(helper.groupedList.size());
+    Set<T> uniquifier = CompactHashSet.createWithExpectedSize(helper.elements.size());
     for (Object item : helper.groupedList) {
       if (item instanceof List) {
         // Optimize for the case that elements in this list are unique.
         ImmutableList.Builder<T> dedupedList = null;
         List<T> list = (List<T>) item;
+        Preconditions.checkState(
+            list.size() > 1, "Helper should have compressed small list %s properly", list);
         for (int i = 0; i < list.size(); i++) {
           T elt = list.get(i);
           if (!uniquifier.add(elt)) {
@@ -87,9 +89,7 @@ public class GroupedList<T> implements Iterable<Collection<T>> {
           elements.add(list);
         } else {
           List<T> filteredList = dedupedList.build();
-          if (!filteredList.isEmpty()) {
-            elements.add(filteredList);
-          }
+          addItem(filteredList, elements);
         }
       } else if (uniquifier.add((T) item)) {
         elements.add(item);