Allow interface classes named package-info without ACC_ABSTRACT

This was already handled on then DEX and R8 case by adding the
ACC_ABSTRACT flag. In D8 Cf to Cf  desugaring do a pass through
keeping the interface without ACC_ABSTRACT.

Fixes: b/234792931
Change-Id: Iac39c48dc07beff5448c6765b88b140fa1bfbecf

src/main/java/com/android/tools/r8/jar/CfApplicationWriter.java

diff --git a/src/main/java/com/android/tools/r8/jar/CfApplicationWriter.java b/src/main/java/com/android/tools/r8/jar/CfApplicationWriter.java
index d576801..cdb9762 100644
--- a/src/main/java/com/android/tools/r8/jar/CfApplicationWriter.java
+++ b/src/main/java/com/android/tools/r8/jar/CfApplicationWriter.java
@@ -243,8 +243,15 @@
         clazz.accessFlags.setSuper();
       }
     }
+    boolean allowInvalidCfAccessFlags = false;
+    if (clazz
+        .getType()
+        .getDescriptor()
+        .endsWith(appView.dexItemFactory().createString("/package-info;"))) {
+      allowInvalidCfAccessFlags = true;
+    }
     int access =
-        options.testing.allowInvalidCfAccessFlags
+        allowInvalidCfAccessFlags || options.testing.allowInvalidCfAccessFlags
             ? clazz.accessFlags.materialize()
             : clazz.accessFlags.getAsCfAccessFlags();
     if (clazz.isDeprecated()) {

src/test/java/com/android/tools/r8/cf/PackageInfoClassFileWithoutAbstractAccessModifierTest.java

diff --git a/src/test/java/com/android/tools/r8/cf/PackageInfoClassFileWithoutAbstractAccessModifierTest.java b/src/test/java/com/android/tools/r8/cf/PackageInfoClassFileWithoutAbstractAccessModifierTest.java
new file mode 100644
index 0000000..0db0bbf
--- /dev/null
+++ b/src/test/java/com/android/tools/r8/cf/PackageInfoClassFileWithoutAbstractAccessModifierTest.java
@@ -0,0 +1,77 @@
+// Copyright (c) 2022, the R8 project authors. Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+package com.android.tools.r8.cf;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.junit.Assert.assertEquals;
+
+import com.android.tools.r8.TestBase;
+import com.android.tools.r8.TestParameters;
+import com.android.tools.r8.utils.AndroidApiLevel;
+import com.android.tools.r8.utils.codeinspector.ClassSubject;
+import com.android.tools.r8.utils.codeinspector.CodeInspector;
+import com.android.tools.r8.utils.codeinspector.Matchers;
+import java.util.List;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+import org.junit.runners.Parameterized.Parameter;
+import org.junit.runners.Parameterized.Parameters;
+import org.objectweb.asm.ClassWriter;
+import org.objectweb.asm.Opcodes;
+
+@RunWith(Parameterized.class)
+public class PackageInfoClassFileWithoutAbstractAccessModifierTest extends TestBase
+    implements Opcodes {
+
+  @Parameter(0)
+  public TestParameters parameters;
+
+  @Parameter(1)
+  public Backend backend;
+
+  @Parameters(name = "{0}")
+  public static List<Object[]> data() {
+    return buildParameters(getTestParameters().withNoneRuntime().build(), Backend.values());
+  }
+
+  private static final String CLASS_NAME = "it.unimi.dsi.fastutil.package-info";
+
+  private void inspect(CodeInspector inspector, boolean isR8) {
+    ClassSubject packageInfo = inspector.clazz(CLASS_NAME);
+    assertThat(packageInfo, Matchers.isInterface());
+    assertEquals(backend.isDex() || isR8, packageInfo.isAbstract());
+  }
+
+  @Test
+  public void testD8() throws Exception {
+    testForD8(backend)
+        .addProgramClassFileData(dump())
+        .setMinApi(AndroidApiLevel.B)
+        .compile()
+        .inspect(inspector -> inspect(inspector, false));
+  }
+
+  @Test
+  public void testR8() throws Exception {
+    testForR8(backend)
+        .addProgramClassFileData(dump())
+        .addKeepMainRule(CLASS_NAME)
+        .setMinApi(AndroidApiLevel.B)
+        .compile()
+        .inspect(inspector -> inspect(inspector, true));
+  }
+
+  // Some versions of javac would generate package-info class files without ACC_ABSTRACT.
+  // Dump of it/unimi/dsi/fastutil/package-info.class from fastutil-8.5.8.jar.
+  public static byte[] dump() throws Exception {
+    ClassWriter classWriter = new ClassWriter(0);
+    classWriter.visit(
+        V1_5, ACC_INTERFACE, "it/unimi/dsi/fastutil/package-info", null, "java/lang/Object", null);
+    classWriter.visitSource("package-info.java", null);
+    classWriter.visitEnd();
+    return classWriter.toByteArray();
+  }
+}