Python Exception MountError: Can't mount widget(s) before Vertical() is mounted upon startup

[xavierog]

Hi,

I installed cliexercices through pipx in a Debian Sid/unstable container and got the following stacktrace when launching it:

[0][12:03:06][user]{fe066b4f7864}~ $ cliexercises
╭──────────────────────────────────────────────────────────────────────────────────────── Traceback (most recent call last) ────────────────────────────────────────────────────────────────────────────────────────╮
│ /home/user/.local/share/pipx/venvs/cliexercises/lib/python3.11/site-packages/cliexercises/cli_exercises.py:87 in on_mount                                                                                         │
│                                                                                                                                                                                                                   │
│    84 │                                                                                        ╭───────────────────────────────── locals ─────────────────────────────────╮                                       │
│    85 │   def on_mount(self):                                                                  │ self = CLIExercisesApp(title='CLIExercisesApp', classes={'-light-mode'}) │                                       │
│    86 │   │   self.dark = self.user_progress.get(-1, False)                                    ╰──────────────────────────────────────────────────────────────────────────╯                                       │
│ ❱  87 │   │   self.set_quest_ip_op()                                                                                                                                                                              │
│    88 │                                                                                                                                                                                                           │
│    89 │   def on_input_submitted(self, event):                                                                                                                                                                    │
│    90 │   │   self.process_user_cmd()                                                                                                                                                                             │
│                                                                                                                                                                                                                   │
│ /home/user/.local/share/pipx/venvs/cliexercises/lib/python3.11/site-packages/cliexercises/cli_exercises.py:153 in set_quest_ip_op                                                                                 │
│                                                                                                                                                                                                                   │
│   150 │   │   │   │   ip_txt = self.trim(f.read())                                             ╭───────────────────────────────────────────── locals ──────────────────────────────────────────────╮              │
│   151 │   │   │   l_ip = Label(ip_txt, classes='ip_op', markup=False)                          │        f = <_io.TextIOWrapper name='ip.txt' mode='r' encoding='ascii'>                            │              │
│   152 │   │   │   l_ip.border_title = ip_file                                                  │  ip_file = 'ip.txt'                                                                               │              │
│ ❱ 153 │   │   │   v_ip.mount(l_ip)                                                             │ ip_files = ['ip.txt']                                                                             │              │
│   154 │   │                                                                                    │   ip_txt = 'hi there\nhow are you\n\n2 apples\n12 bananas\n\n\nblue sky\nyellow sun\nbrown earth' │              │
│   155 │   │   self.op_txt = self.trim(self.questions[self.q_idx]['op_file'])                   │     l_ip = Label()                                                                                │              │
│   156 │   │   l_op = Label(self.op_txt, classes='ip_op', markup=False)                         │     self = CLIExercisesApp(title='CLIExercisesApp', classes={'-light-mode'})                      │              │
│                                                                                                │     v_ip = Vertical()                                                                             │              │
│                                                                                                │     v_op = Vertical()                                                                             │              │
│                                                                                                ╰───────────────────────────────────────────────────────────────────────────────────────────────────╯              │
│                                                                                                                                                                                                                   │
│ /home/user/.local/share/pipx/venvs/cliexercises/lib/python3.11/site-packages/textual/widget.py:938 in mount                                                                                                       │
│                                                                                                                                                                                                                   │
│    935 │   │   │   provided a ``MountError`` will be raised.                                    ╭─────── locals ───────╮                                                                                          │
│    936 │   │   """                                                                              │   after = None       │                                                                                          │
│    937 │   │   if not self.is_attached:                                                         │  before = None       │                                                                                          │
│ ❱  938 │   │   │   raise MountError(f"Can't mount widget(s) before {self!r} is mounted")        │    self = Vertical() │                                                                                          │
│    939 │   │   # Check for duplicate IDs in the incoming widgets                                │ widgets = (Label(),) │                                                                                          │
│    940 │   │   ids_to_mount = [widget.id for widget in widgets if widget.id is not None]        ╰──────────────────────╯                                                                                          │
│    941 │   │   unique_ids = set(ids_to_mount)                                                                                                                                                                     │
╰───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
MountError: Can't mount widget(s) before Vertical() is mounted
[0][12:03:09][user]{fe066b4f7864}~ $

[learnbyexample]

Seems like something has changed in new versions of Textual. I haven't pinned the framework to a particular version (did that because it was convenient for me using pip and a single venv environment to test all of my TUI apps).

I'm not familiar with pipx, but if you are able to install Textual version 0.57.1 (what I last checked) and then install this app in the same environment, it should work.

[learnbyexample]

Relevant discussion: Textualize/textual#4570

[learnbyexample]

I've uploaded a new version of the cliexercises app that takes of the mount issue. Let me know if it works on your end.

The same problem is present in some of the other apps as well, so I'll keep this issue open until they are fixed.

[xavierog]

I've uploaded a new version of the cliexercises app that takes of the mount issue. Let me know if it works on your end.

Yes, I confirm cliexercises 2.2.0 works as expected.