fix: Need a way to find the main user via shell

Bug: 265042334
Test: manual `adb shell cmd user get-main-user`
Change-Id: Ifa58a6b4a425948e07427c6d8dd979fc0b48e653

services/core/java/com/android/server/pm/UserManagerServiceShellCommand.java

@@ -116,6 +116,9 @@ public class UserManagerServiceShellCommand extends ShellCommand {
         pw.println("    If the display option is not set, it uses the user's context to check");
         pw.println("    (so it emulates what apps would get from UserManager.isUserVisible())");
         pw.println();
+        pw.println("  get-main-user ");
+        pw.println("    Displays main user id or message if there is no main user");
+        pw.println();
     }
 
     @Override
@@ -138,6 +141,8 @@ public class UserManagerServiceShellCommand extends ShellCommand {
                     return runIsVisibleBackgroundUserOnDefaultDisplaySupported();
                 case "is-user-visible":
                     return runIsUserVisible();
+                case "get-main-user":
+                    return runGetMainUserId();
                 default:
                     return handleDefaultCommands(cmd);
             }
@@ -479,6 +484,17 @@ public class UserManagerServiceShellCommand extends ShellCommand {
         return 0;
     }
 
+    private int runGetMainUserId() {
+        PrintWriter pw = getOutPrintWriter();
+        final int mainUserId = mService.getMainUserId();
+        if (mainUserId == UserHandle.USER_NULL) {
+            pw.println("Couldn't get main user.");
+            return 1;
+        }
+        pw.println("Main user id: " + mainUserId);
+        return 0;
+    }
+
     /**
      * Gets the {@link UserManager} associated with the context of the given user.
      */

services/tests/servicestests/src/com/android/server/pm/UserManagerServiceShellCommandTest.java

@@ -0,0 +1,124 @@
+/*
+ * Copyright (C) 2023 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package com.android.server.pm;
+
+import static junit.framework.Assert.assertEquals;
+
+import static org.mockito.Mockito.doReturn;
+import static org.mockito.Mockito.spy;
+import static org.mockito.Mockito.when;
+
+import static java.io.FileDescriptor.err;
+import static java.io.FileDescriptor.in;
+import static java.io.FileDescriptor.out;
+
+import android.app.PropertyInvalidatedCache;
+import android.content.Context;
+import android.os.Binder;
+import android.os.Handler;
+import android.os.Looper;
+import android.os.ResultReceiver;
+import android.os.ShellCallback;
+import android.os.UserHandle;
+import android.platform.test.annotations.Presubmit;
+import android.util.ArrayMap;
+
+import androidx.test.InstrumentationRegistry;
+import androidx.test.runner.AndroidJUnit4;
+
+import com.android.internal.widget.LockPatternUtils;
+import com.android.server.LocalServices;
+
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.mockito.Mock;
+import org.mockito.MockitoAnnotations;
+
+import java.io.ByteArrayOutputStream;
+import java.io.PrintStream;
+import java.io.PrintWriter;
+
+/**
+ * Test class for {@link UserManagerServiceShellCommand}.
+ *
+ * runtest atest UserManagerServiceShellCommandTest
+ */
+@Presubmit
+@RunWith(AndroidJUnit4.class)
+public class UserManagerServiceShellCommandTest {
+
+    private UserManagerServiceShellCommand mCommand;
+    private UserManagerService mUserManagerService;
+    private @Mock LockPatternUtils mLockPatternUtils;
+    private final Binder mBinder = new Binder();
+    private final ShellCallback mShellCallback = new ShellCallback();
+    private final ResultReceiver mResultReceiver = new ResultReceiver(
+            new Handler(Looper.getMainLooper()));
+    private ByteArrayOutputStream mOutStream;
+    private PrintWriter mWriter;
+
+    @Before
+    public void setUp() throws Exception {
+        mOutStream = new ByteArrayOutputStream();
+        mWriter = new PrintWriter(new PrintStream(mOutStream));
+        MockitoAnnotations.initMocks(this);
+
+        if (Looper.myLooper() == null) {
+            Looper.prepare();
+        }
+        // Disable binder caches in this process.
+        PropertyInvalidatedCache.disableForTestMode();
+
+        LocalServices.removeServiceForTest(UserManagerInternal.class);
+        final Context context = InstrumentationRegistry.getTargetContext();
+
+        UserManagerService serviceInstance = new UserManagerService(context);
+        mUserManagerService = spy(serviceInstance);
+
+        ArrayMap<String, UserTypeDetails> userTypes = UserTypeFactory.getUserTypes();
+        UserSystemPackageInstaller userSystemPackageInstaller =
+                new UserSystemPackageInstaller(mUserManagerService, userTypes);
+        UserManagerServiceShellCommand cmd = new UserManagerServiceShellCommand(mUserManagerService,
+                userSystemPackageInstaller, mLockPatternUtils, context);
+        mCommand = spy(cmd);
+    }
+
+    @Test
+    public void testMainUser() {
+        when(mUserManagerService.getMainUserId()).thenReturn(12);
+        doReturn(mWriter).when(mCommand).getOutPrintWriter();
+
+        assertEquals(0, mCommand.exec(mBinder, in, out, err,
+                new String[]{"get-main-user"}, mShellCallback, mResultReceiver));
+
+        mWriter.flush();
+        assertEquals("Main user id: 12", mOutStream.toString().trim());
+    }
+
+    @Test
+    public void testMainUserNull() {
+        when(mUserManagerService.getMainUserId()).thenReturn(UserHandle.USER_NULL);
+        doReturn(mWriter).when(mCommand).getOutPrintWriter();
+
+        assertEquals(1, mCommand.exec(mBinder, in, out, err,
+                new String[]{"get-main-user"}, mShellCallback, mResultReceiver));
+        mWriter.flush();
+        assertEquals("Couldn't get main user.", mOutStream.toString().trim());
+    }
+
+}