Added restriction for switching to Headless SYSTEM user.

On HSUM(HeadlessSystemUserMode) user 0 will not be a Full user and is
not going to run in foreground.
Added restrictions to prevent switching to non-full user
which will eventually restrict switching to user 0 in headless.

In some form factors we do need to switch to headless SYSTEM user even when its not FULL like in AUTO, added overlay property to allow switching to non-full SYSTEM user in case the property is enabled.

Refactor and Deprecated UserInfo.supportsSwitchToByUser by UserInfo.supportsSwitchTo after adding the restrictions to prevent switch to non-full users.

Removed redundant userInfo.isProfile check from UserController.switchUser.

Test: m , atest ActivityManagerTest -c
Bug: 262402637
Change-Id: I871e6721ce6745d5a9e3009162e3d6ac8a284908

core/api/test-current.txt

@@ -923,7 +923,7 @@ package android.content.pm {
     method public boolean isQuietModeEnabled();
     method public boolean isRestricted();
     method public boolean supportsSwitchTo();
-    method public boolean supportsSwitchToByUser();
+    method @Deprecated public boolean supportsSwitchToByUser();
     method public void writeToParcel(android.os.Parcel, int);
     field @NonNull public static final android.os.Parcelable.Creator<android.content.pm.UserInfo> CREATOR;
     field public static final int FLAG_ADMIN = 2; // 0x2

core/java/android/content/pm/UserInfo.java

@@ -22,6 +22,7 @@ import android.annotation.Nullable;
 import android.annotation.TestApi;
 import android.annotation.UserIdInt;
 import android.compat.annotation.UnsupportedAppUsage;
+import android.content.res.Resources;
 import android.os.Parcel;
 import android.os.Parcelable;
 import android.os.UserHandle;
@@ -418,16 +419,25 @@ public class UserInfo implements Parcelable {
             // Don't support switching to pre-created users until they become "real" users.
             return false;
         }
-        return !isProfile();
+        return isFull() || canSwitchToHeadlessSystemUser();
+    }
+
+    /**
+     * @return true if user is of type {@link UserManager#USER_TYPE_SYSTEM_HEADLESS} and
+     * {@link com.android.internal.R.bool.config_canSwitchToHeadlessSystemUser} is true.
+     */
+    private boolean canSwitchToHeadlessSystemUser() {
+        return UserManager.USER_TYPE_SYSTEM_HEADLESS.equals(userType) && Resources.getSystem()
+                .getBoolean(com.android.internal.R.bool.config_canSwitchToHeadlessSystemUser);
     }
 
     /**
      * @return true if this user can be switched to by end user through UI.
+     * @deprecated Use {@link UserInfo#supportsSwitchTo} instead.
      */
+    @Deprecated
     public boolean supportsSwitchToByUser() {
-        // Hide the system user when it does not represent a human user.
-        boolean hideSystemUser = UserManager.isHeadlessSystemUserMode();
-        return (!hideSystemUser || id != UserHandle.USER_SYSTEM) && supportsSwitchTo();
+        return supportsSwitchTo();
     }
 
     // TODO(b/142482943): Make this logic more specific and customizable. (canHaveProfile(userType))

core/res/res/values/config.xml

@@ -2774,6 +2774,10 @@
      it can't be deleted or downgraded to non-admin status. -->
     <bool name="config_isMainUserPermanentAdmin">false</bool>
 
+    <!-- Whether switch to headless system user is allowed. If allowed,
+    headless system user can run in the foreground even though it is not a full user. -->
+    <bool name="config_canSwitchToHeadlessSystemUser">false</bool>
+
     <!-- Whether UI for multi user should be shown -->
     <bool name="config_enableMultiUserUI">false</bool>
 

core/res/res/values/symbols.xml

@@ -355,6 +355,7 @@
   <java-symbol type="bool" name="config_speed_up_audio_on_mt_calls" />
   <java-symbol type="bool" name="config_useFixedVolume" />
   <java-symbol type="bool" name="config_isMainUserPermanentAdmin"/>
+  <java-symbol type="bool" name="config_canSwitchToHeadlessSystemUser"/>
   <java-symbol type="bool" name="config_enableMultiUserUI"/>
   <java-symbol type="bool" name="config_enableMultipleAdmins"/>
   <java-symbol type="bool" name="config_enableNewAutoSelectNetworkUI"/>

services/core/java/com/android/server/am/UserController.java

@@ -1984,10 +1984,6 @@ class UserController implements Handler.Callback {
             Slogf.w(TAG, "Cannot switch to User #" + targetUserId + ": not supported");
             return false;
         }
-        if (targetUserInfo.isProfile()) {
-            Slogf.w(TAG, "Cannot switch to User #" + targetUserId + ": not a full user");
-            return false;
-        }
         if (FactoryResetter.isFactoryResetting()) {
             Slogf.w(TAG, "Cannot switch to User #" + targetUserId + ": factory reset in progress");
             return false;