app: Add ability to hide configuration form when app is disabled

- Some apps store their configuration in database. The database server may not
be running when app is disabled. Configuration changes may then not be
possible for such apps. Provide the ability to disable configuration for apps
that don't support configuration changes when disabled.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/app.py

@@ -42,6 +42,10 @@ class App:
     the app. This flag is currently set during backup and restore operations
     but UI changes are currently not implemented.
 
+    'configure_when_disabled' is a boolean indicating whether the app can
+    configured while it is disabled. Some apps such those whose configuration
+    is stored in a database can't be configured while they are disabled because
+    the database server may not be running when the app is disabled.
     """
 
     app_id: str | None = None
@@ -51,6 +55,8 @@ class App:
     locked: bool = False  # Whether user interaction with the app is allowed.
     # XXX: Lockdown the application UI by implementing a middleware
 
+    configure_when_disabled: bool = True
+
     _all_apps: ClassVar[collections.OrderedDict[
         str, 'App']] = collections.OrderedDict()
 

plinth/tests/test_app.py

@@ -67,6 +67,9 @@ def test_app_instantiation():
     assert app.app_id == 'test-app'
     assert app._all_apps['test-app'] == app
     assert len(app._all_apps) == 1
+    assert app.can_be_disabled
+    assert not app.locked
+    assert app.configure_when_disabled
 
 
 def test_app_get():

plinth/views.py

@@ -215,6 +215,11 @@ class AppView(FormView):
         if not self.form_class:
             return None
 
+        if not self.app.configure_when_disabled:
+            status = self.get_common_status()
+            if not status['is_enabled']:
+                return None
+
         return super().get_form(*args, **kwargs)
 
     def _get_common_status(self):