Update nullability of extension versions in Rollback.

This updates nullability annotations in Rollback and RollbackStore as
suggested in comments on ag/11256434.

Bug: 152737927
Test: atest RollbackUnitTest
Test: atest RollbackTest
Test: atest RollbackStoreTest
Change-Id: Ib0973378fdd24ce275b0f3e1a687f9161d3c0e7d

services/core/java/com/android/server/rollback/Rollback.java

@@ -59,6 +59,7 @@ import java.text.ParseException;
 import java.time.Instant;
 import java.util.ArrayList;
 import java.util.List;
+import java.util.Objects;
 
 
 /**
@@ -182,7 +183,7 @@ class Rollback {
     /**
      * The extension versions supported at the time of rollback creation.
      */
-    private final SparseIntArray mExtensionVersions;
+    @NonNull private final SparseIntArray mExtensionVersions;
 
     /**
      * Constructs a new, empty Rollback instance.
@@ -210,7 +211,7 @@ class Rollback {
         mState = ROLLBACK_STATE_ENABLING;
         mTimestamp = Instant.now();
         mPackageSessionIds = packageSessionIds != null ? packageSessionIds : new int[0];
-        mExtensionVersions = extensionVersions;
+        mExtensionVersions = Objects.requireNonNull(extensionVersions);
     }
 
     Rollback(int rollbackId, File backupDir, int stagedSessionId, int userId,
@@ -234,7 +235,7 @@ class Rollback {
         mState = state;
         mApkSessionId = apkSessionId;
         mRestoreUserDataInProgress = restoreUserDataInProgress;
-        mExtensionVersions = extensionVersions;
+        mExtensionVersions = Objects.requireNonNull(extensionVersions);
         // TODO(b/120200473): Include this field during persistence. This field will be used to
         // decide which rollback to expire when ACTION_PACKAGE_REPLACED is received. Note persisting
         // this field is not backward compatible. We won't fix b/120200473 until S to minimize the

services/core/java/com/android/server/rollback/RollbackStore.java

@@ -21,7 +21,6 @@ import static android.os.UserHandle.USER_SYSTEM;
 import static com.android.server.rollback.Rollback.rollbackStateFromString;
 
 import android.annotation.NonNull;
-import android.annotation.Nullable;
 import android.content.pm.PackageManager;
 import android.content.pm.VersionedPackage;
 import android.content.rollback.PackageRollbackInfo;
@@ -178,7 +177,7 @@ class RollbackStore {
         return ceSnapshotInodes;
     }
 
-    private static @Nullable JSONArray extensionVersionsToJson(
+    private static @NonNull JSONArray extensionVersionsToJson(
             SparseIntArray extensionVersions) throws JSONException {
         JSONArray array = new JSONArray();
         for (int i = 0; i < extensionVersions.size(); i++) {
@@ -190,7 +189,7 @@ class RollbackStore {
         return array;
     }
 
-    private static @Nullable SparseIntArray extensionVersionsFromJson(JSONArray json)
+    private static @NonNull SparseIntArray extensionVersionsFromJson(JSONArray json)
             throws JSONException {
         if (json == null) {
             return new SparseIntArray(0);

services/tests/servicestests/src/com/android/server/rollback/RollbackUnitTest.java

@@ -331,7 +331,7 @@ public class RollbackUnitTest {
     public void notifySessionWithSuccess() {
         int[] sessionIds = new int[]{ 7777, 8888 };
         Rollback rollback = new Rollback(123, new File("/test/testing"), -1, USER, INSTALLER,
-                sessionIds, null);
+                sessionIds, new SparseIntArray(0));
         // The 1st invocation returns false because not all child sessions are notified.
         assertThat(rollback.notifySessionWithSuccess()).isFalse();
         // The 2nd invocation returns true because now all child sessions are notified.
@@ -342,7 +342,7 @@ public class RollbackUnitTest {
     public void allPackagesEnabled() {
         int[] sessionIds = new int[]{ 7777, 8888 };
         Rollback rollback = new Rollback(123, new File("/test/testing"), -1, USER, INSTALLER,
-                sessionIds, null);
+                sessionIds, new SparseIntArray(0));
         // #allPackagesEnabled returns false when 1 out of 2 packages is enabled.
         rollback.info.getPackages().add(newPkgInfoFor(PKG_1, 12, 10, false));
         assertThat(rollback.allPackagesEnabled()).isFalse();