IssueTracker

A recent change in D8 changed the class names generated for synthetic classes including lambdas. Now the following three names can be present:

  A$1.class
  A-$$ExternalSyntheticLambda0.class
  A.class

The sorting used is not transitive with these names.

In some settings D8 desugars to class file and not directly to DEX, and if the desugared class files are passed to lint then the following exception can happen:

java.lang.IllegalArgumentException: Comparison method violates its general contract!
	at java.base/java.util.ComparableTimSort.mergeLo(ComparableTimSort.java:748)
	at java.base/java.util.ComparableTimSort.mergeAt(ComparableTimSort.java:485)
	at java.base/java.util.ComparableTimSort.mergeCollapse(ComparableTimSort.java:413)
	at java.base/java.util.ComparableTimSort.sort(ComparableTimSort.java:213)
	at java.base/java.util.Arrays.sort(Arrays.java:1316)
	at java.base/java.util.Arrays.sort(Arrays.java:1510)
	at java.base/java.util.ArrayList.sort(ArrayList.java:1751)
	at java.base/java.util.Collections.sort(Collections.java:145)
	at com.android.tools.lint.client.api.ClassEntry.fromClassPath(ClassEntry.java:120)
	at com.android.tools.lint.client.api.LintDriver.checkClasses(LintDriver.kt:1361)
	at com.android.tools.lint.client.api.LintDriver.runFileDetectors(LintDriver.kt:1146)
	at com.android.tools.lint.client.api.LintDriver.checkProject(LintDriver.kt:908)
	at com.android.tools.lint.client.api.LintDriver.analyze(LintDriver.kt:422)
	at com.android.tools.lint.LintCliClient.run(LintCliClient.kt:223)
	at com.android.tools.lint.Main.run(Main.java:1337)
	at com.android.tools.lint.Main.run(Main.java:241)
	at com.android.tools.lint.Main.main(Main.java:189)

See b/178715340.

Always sorting '.' lowest - as in the following patch (which fixes b/178715340) - could be an option, but I am not familiar with the internal order requirements in lint.

diff --git a/lint/libs/lint-api/src/main/java/com/android/tools/lint/client/api/ClassEntry.java b/lint/libs/lint-api/src/main/java/com/android/tools/lint/client/api/ClassEntry.java
index 13bb4925ee..e0f70a939f 100644
--- a/lint/libs/lint-api/src/main/java/com/android/tools/lint/client/api/ClassEntry.java
+++ b/lint/libs/lint-api/src/main/java/com/android/tools/lint/client/api/ClassEntry.java
@@ -82,16 +82,14 @@ class ClassEntry implements Comparable<ClassEntry> {
         for (int i = 0; i < m; i++) {
             char c1 = p1.charAt(i);
             char c2 = p2.charAt(i);
-            if (c1 != c2) {
-                // Sort Foo$Bar.class *after* Foo.class, even though $ < .
-                if (c1 == '.' && c2 == '$') {
-                    return -1;
-                }
-                if (c1 == '$' && c2 == '.') {
-                    return 1;
-                }
-                return c1 - c2;
+            // Sort Foo$Bar.class *after* Foo.class, even though $ < .
+            if (c1 == '.') {
+                c1 = 0;
+            }
+            if (c2 == '.') {
+                c2 = 0;
             }
+            return c1 - c2;
         }
 
         return (m == m1) ? -1 : 1;