From aae7c2417597a2b0607252742def6130c7f544d9 Mon Sep 17 00:00:00 2001
From: Patrick Strawderman <pstrawderman@netflix.com>
Date: Wed, 28 Sep 2022 13:19:50 -0700
Subject: [PATCH] Fix Spliterator implementations for sorted collections

Spliterators returned by CollectSpliterators.indexed and ImmutableSortedSet.spliterator
violated the Spliterator API by not returning null in getComparator when the source
items are naturally sorted. The effect was that sort operations on Streams backed by
these Spliterators were not optimized away, resulting in additional unnecessary sorting.

Fixes #6187.
---
 guava/src/com/google/common/collect/CollectSpliterators.java | 2 +-
 guava/src/com/google/common/collect/ImmutableSortedSet.java  | 3 ++-
 2 files changed, 3 insertions(+), 2 deletions(-)

diff --git a/guava/src/com/google/common/collect/CollectSpliterators.java b/guava/src/com/google/common/collect/CollectSpliterators.java
index 7d0e82f203a8..db6dce694c0e 100644
--- a/guava/src/com/google/common/collect/CollectSpliterators.java
+++ b/guava/src/com/google/common/collect/CollectSpliterators.java
@@ -96,7 +96,7 @@ public int characteristics() {
       @CheckForNull
       public Comparator<? super T> getComparator() {
         if (hasCharacteristics(Spliterator.SORTED)) {
-          return comparator;
+          return Ordering.natural().equals(comparator) ? null : comparator;
         } else {
           throw new IllegalStateException();
         }
diff --git a/guava/src/com/google/common/collect/ImmutableSortedSet.java b/guava/src/com/google/common/collect/ImmutableSortedSet.java
index 20d007271298..ed3554193838 100644
--- a/guava/src/com/google/common/collect/ImmutableSortedSet.java
+++ b/guava/src/com/google/common/collect/ImmutableSortedSet.java
@@ -805,8 +805,9 @@ public boolean tryAdvance(Consumer<? super E> action) {
       }
 
       @Override
+      @CheckForNull
       public Comparator<? super E> getComparator() {
-        return comparator;
+        return Ordering.natural().equals(comparator) ? null : comparator;
       }
     };
   }