Prevent deleting folders with children

FAQ.md

@@ -109,7 +109,7 @@ Related questions:
 * Load more messages: long press a folder in the folder list, select *Fetch more messages*
 * Delete a message, skipping trash: long press the trash icon
 * Delete an account/identity: (Main) Settings, tap Manual setup, tap Accounts/Identities, tap the account/identity, tap the trash icon in the top right corner
-* Delete a folder: long press the folder in the folder list, Edit properties, tap the trash icon in the top right corner
+* Delete a folder: long press the folder in the folder list, Edit properties, tap the trash icon in the top right corner. Note that you can't delete folders which still have sub folders.
 * Undo send: Outbox, swipe the message in the list left or right
 * Delete a contact: please [see this FAQ](#faq171)
 * Store sent messages in the inbox: please [see this FAQ](#faq142)

app/src/main/java/eu/faircode/email/AdapterFolder.java

@@ -730,7 +730,8 @@ public class AdapterFolder extends RecyclerView.Adapter<AdapterFolder.ViewHolder
             if (folder.selectable && Shortcuts.can(context))
                 popupMenu.getMenu().add(Menu.NONE, R.string.title_pin, order++, R.string.title_pin);
 
-            if (!folder.read_only && EntityFolder.USER.equals(folder.type))
+            if (!folder.read_only && EntityFolder.USER.equals(folder.type) &&
+                    (folder.child_refs == null || folder.child_refs.isEmpty()))
                 popupMenu.getMenu().add(Menu.NONE, R.string.title_delete, order++, R.string.title_delete);
 
             popupMenu.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {

app/src/main/java/eu/faircode/email/FragmentFolder.java

@@ -52,6 +52,7 @@ import androidx.preference.PreferenceManager;
 
 import com.google.android.material.snackbar.Snackbar;
 
+import java.util.List;
 import java.util.Objects;
 
 public class FragmentFolder extends FragmentBase {
@@ -301,6 +302,9 @@ public class FragmentFolder extends FragmentBase {
                 EntityFolder parent = db.folder().getFolderByName(aid, parentName);
                 EntityFolder folder = db.folder().getFolder(id);
 
+                List<EntityFolder> children = db.folder().getChildFolders(id);
+                args.putBoolean("children", (children != null && !children.isEmpty()));
+
                 if (folder != null) {
                     EntityAccount account = db.account().getAccount(folder.account);
                     if (account != null) {
@@ -377,7 +381,8 @@ public class FragmentFolder extends FragmentBase {
 
                 deletable = (folder != null &&
                         !folder.read_only &&
-                        EntityFolder.USER.equals(folder.type));
+                        EntityFolder.USER.equals(folder.type) &&
+                        !args.getBoolean("children"));
                 invalidateOptionsMenu();
             }
 

index.html

@@ -121,7 +121,7 @@
 <li>Load more messages: long press a folder in the folder list, select <em>Fetch more messages</em></li>
 <li>Delete a message, skipping trash: long press the trash icon</li>
 <li>Delete an account/identity: (Main) Settings, tap Manual setup, tap Accounts/Identities, tap the account/identity, tap the trash icon in the top right corner</li>
-<li>Delete a folder: long press the folder in the folder list, Edit properties, tap the trash icon in the top right corner</li>
+<li>Delete a folder: long press the folder in the folder list, Edit properties, tap the trash icon in the top right corner. Note that you can’t delete folders which still have sub folders.</li>
 <li>Undo send: Outbox, swipe the message in the list left or right</li>
 <li>Delete a contact: please <a href="#faq171">see this FAQ</a></li>
 <li>Store sent messages in the inbox: please <a href="#faq142">see this FAQ</a></li>