From 140e6c0c407250c09d6fc931c70a0360c1b1c3e5 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=E9=BE=9A=E6=8C=AF?= <oscar.Gong@gmail.com>
Date: Fri, 21 Aug 2026 17:36:10 +0800
Subject: [PATCH] Fix DexFileSplitter class name collisions

Fall back to the original class names when lossy dx-style normalization produces an equal result, so TreeMap does not drop distinct entries.
---
 .../build/android/dexer/ZipEntryComparator.java    | 12 +++++++++++-
 .../build/android/dexer/DexFileSplitterTest.java   | 14 ++++++++++++++
 2 files changed, 25 insertions(+), 1 deletion(-)

diff --git a/src/tools/java/com/google/devtools/build/android/dexer/ZipEntryComparator.java b/src/tools/java/com/google/devtools/build/android/dexer/ZipEntryComparator.java
index ab0b83899..db95db4ab 100644
--- a/src/tools/java/com/google/devtools/build/android/dexer/ZipEntryComparator.java
+++ b/src/tools/java/com/google/devtools/build/android/dexer/ZipEntryComparator.java
@@ -44,6 +44,9 @@ public int compare(ZipEntry a, ZipEntry b) {
   // Copied from com.android.dx.cf.direct.ClassPathOpener
   @VisibleForTesting
   static int compareClassNames(String a, String b) {
+    String originalA = a;
+    String originalB = b;
+
     // Ensure inner classes sort second
     a = a.replace('$', '0');
     b = b.replace('$', '0');
@@ -55,6 +58,13 @@ static int compareClassNames(String a, String b) {
     a = a.replace("package-info", "");
     b = b.replace("package-info", "");
 
-    return a.compareTo(b);
+    int normalizedResult = a.compareTo(b);
+    if (normalizedResult != 0) {
+      return normalizedResult;
+    }
+
+    // Normalization is lossy. Keep distinct raw names distinct when this comparator is used as a
+    // TreeMap key comparator, otherwise entries such as Foo$2$1$1 and Foo$2$101 collapse.
+    return originalA.compareTo(originalB);
   }
 }
diff --git a/src/tools/javatests/com/google/devtools/build/android/dexer/DexFileSplitterTest.java b/src/tools/javatests/com/google/devtools/build/android/dexer/DexFileSplitterTest.java
index 1551df2de..5784e876e 100644
--- a/src/tools/javatests/com/google/devtools/build/android/dexer/DexFileSplitterTest.java
+++ b/src/tools/javatests/com/google/devtools/build/android/dexer/DexFileSplitterTest.java
@@ -29,6 +29,7 @@
 import java.nio.file.Path;
 import java.util.HashSet;
 import java.util.Set;
+import java.util.TreeMap;
 import java.util.concurrent.ExecutionException;
 import java.util.zip.CRC32;
 import java.util.zip.ZipEntry;
@@ -123,6 +124,19 @@ public void testDuplicateInputIgnored() throws Exception {
     assertThat(dexEntries(outputArchives.get(0))).containsExactlyElementsIn(expectedFiles);
   }
 
+  @Test
+  public void testClassNameComparatorPreservesNormalizationCollisions() {
+    TreeMap<String, Boolean> classNames =
+        new TreeMap<>(ZipEntryComparator::compareClassNames);
+
+    classNames.put("Foo$2$1$1.class.dex", true);
+    classNames.put("Foo$2$101.class.dex", true);
+
+    assertThat(classNames.keySet())
+        .containsExactly("Foo$2$1$1.class.dex", "Foo$2$101.class.dex")
+        .inOrder();
+  }
+
   @Test
   public void testSingleInputMultidexOutput() throws Exception {
     ImmutableList<Path> outputArchives =