Try/except on all app

[mattthhh]

Hi there! I wanted to know if there is a solution to catch all exceptions from the whole app running, I tried this code following :

if __name__ == "__main__":
    try:
        app = App()
        ret = app.run()
    except Exception as err:
        print("sad")

but it didn't work... I got the exception with rich printing but it's not handled by my try/except in my main. Any ideas ?

[davep]

Generally I think it's fair to say that the best idea is to catch exceptions as close to their source as possible, and then handle them gracefully. Textual, as you can see, has a catch-all handler that reports the error. I don't believe there's a direct method of turning it off, but you could probably override App._fatal_error (which is at the heart of this) and do something with it. For example:

import sys

from textual.app import App

class BadApp(App[None]):

    def on_mount(self) -> None:
        _ = 1/0

    def _fatal_error(self) -> None:
        super()._fatal_error()
        self._exit_renderables = []
        _, exception, _ = sys.exc_info()
        if exception is not None:
            raise exception

if __name__ == "__main__":
    try:
        BadApp().run()
    except Exception as error:
        print(error)

This, of course, has the downside of overriding an internal method, but I suspect this will be stable.

[mattthhh]

Okay, one more little problem is that now the dump is printed twice :

╭────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── Traceback (most recent call last) ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ ***:193 in on_option_list_option_highlighted                                                                                                                                                                                                  │
│                                                                                                                                                                                                                                                                                │
│   190 │   │   log.write(entry.description)                                                     ╭──────────────────────────────────────────────────────────────── locals ────────────────────────────────────────────────────────────────╮                                      │
│   191 │   │   styles = event.option_list.get_component_styles(                                 │  entry = <json_file.Menu object at 0x7f91852cf1d0>                                                                                     │                                      │
│   192 │   │   │   "option-list--option-highlighted")                                           │  event = OptionHighlighted(option_list=OptionList(), option=Option(prompt='Modules'), option_id=None, option_index=0)                  │                                      │
│ ❱ 193 │   │   self.__colorOptionList(styles, Type.MENU)                                        │    log = MyLog()                                                                                                                       │                                      │
│   194 │   │   if len(pl.stack) == 1:                                                           │     pl = PathLabel()                                                                                                                   │                                      │
│   195 │   │   │   self.update_bindings(                                                        │   self = Sam(title='sam', classes={'-dark-mode'})                                                                                      │                                      │
│   196 │   │   │   │   [("escape", "back", "Exit"), ("slash", "command_palette", "Search")])    │ styles = RenderStyles(auto_color=True, color=Color(255, 255, 255, a=0.87), background=Color(1, 120, 212), text_style=Style(bold=True)) │                                      │
│                                                                                                ╰────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯                                      │
│                                                                                                                                                                                                                                                                                │
│ ***:399 in __colorOptionList                                                                                                                                                                                                                  │
│                                                                                                                                                                                                                                                                                │
│   396 │   │   """                                                                              ╭──────────────────────────────────────────────────────────────── locals ────────────────────────────────────────────────────────────────╮                                      │
│   397 │   │   styles.background = Color(1, 120, 212)                                           │   self = Sam(title='sam', classes={'-dark-mode'})                                                                                      │                                      │
│   398 │   │   # ol = self.query_one(OptionList)                                                │ styles = RenderStyles(auto_color=True, color=Color(255, 255, 255, a=0.87), background=Color(1, 120, 212), text_style=Style(bold=True)) │                                      │
│ ❱ 399 │   │   ol.styles.border = ("tall", Color(1, 120, 212))                                  │   type = <Type.MENU: 1>                                                                                                                │                                      │
│   400 │   │   if type is Type.COMMAND:                                                         ╰────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯                                      │
│   401 │   │   │   styles.background = "limegreen"                                                                                                                                                                                                                              │
│   402 │   │   │   ol.styles.border = ("tall", "limegreen")                                                                                                                                                                                                                     │
╰────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
NameError: name 'ol' is not defined
╭────────────────────────────────────────────────────────────────────────────────────────────────────────────────────── Traceback (most recent call last) ───────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╮
│ ***:193 in on_option_list_option_highlighted                                                                                                                                                                                                  │
│                                                                                                                                                                                                                                                                                │
│   190 │   │   log.write(entry.description)                                                     ╭──────────────────────────────────────────────────────────────── locals ────────────────────────────────────────────────────────────────╮                                      │
│   191 │   │   styles = event.option_list.get_component_styles(                                 │  entry = <json_file.Menu object at 0x7f91852cf1d0>                                                                                     │                                      │
│   192 │   │   │   "option-list--option-highlighted")                                           │  event = OptionHighlighted(option_list=OptionList(), option=Option(prompt='Modules'), option_id=None, option_index=0)                  │                                      │
│ ❱ 193 │   │   self.__colorOptionList(styles, Type.MENU)                                        │    log = MyLog()                                                                                                                       │                                      │
│   194 │   │   if len(pl.stack) == 1:                                                           │     pl = PathLabel()                                                                                                                   │                                      │
│   195 │   │   │   self.update_bindings(                                                        │   self = Sam(title='sam', classes={'-dark-mode'})                                                                                      │                                      │
│   196 │   │   │   │   [("escape", "back", "Exit"), ("slash", "command_palette", "Search")])    │ styles = RenderStyles(auto_color=True, color=Color(255, 255, 255, a=0.87), background=Color(1, 120, 212), text_style=Style(bold=True)) │                                      │
│                                                                                                ╰────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯                                      │
│                                                                                                                                                                                                                                                                                │
│ ***:399 in __colorOptionList                                                                                                                                                                                                                  │
│                                                                                                                                                                                                                                                                                │
│   396 │   │   """                                                                              ╭──────────────────────────────────────────────────────────────── locals ────────────────────────────────────────────────────────────────╮                                      │
│   397 │   │   styles.background = Color(1, 120, 212)                                           │   self = Sam(title='sam', classes={'-dark-mode'})                                                                                      │                                      │
│   398 │   │   # ol = self.query_one(OptionList)                                                │ styles = RenderStyles(auto_color=True, color=Color(255, 255, 255, a=0.87), background=Color(1, 120, 212), text_style=Style(bold=True)) │                                      │
│ ❱ 399 │   │   ol.styles.border = ("tall", Color(1, 120, 212))                                  │   type = <Type.MENU: 1>                                                                                                                │                                      │
│   400 │   │   if type is Type.COMMAND:                                                         ╰────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯                                      │
│   401 │   │   │   styles.background = "limegreen"                                                                                                                                                                                                                              │
│   402 │   │   │   ol.styles.border = ("tall", "limegreen")                                                                                                                                                                                                                     │
╰────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────────╯
NameError: name 'ol' is not defined

NOTE: 2 errors shown above.

[davep]

Not sure why that would be. With this code:

import sys

from textual.app import App

class BadApp(App[None]):

    def on_mount(self) -> None:
        _ = 1/0

    def _fatal_error(self) -> None:
        super()._fatal_error()
        _, exception, _ = sys.exc_info()
        if exception is not None:
            raise exception

if __name__ == "__main__":
    try:
        BadApp().run()
    except Exception as error:
        print("Something bad happened :-(")

I only get it the once:

[mattthhh]

Yeah interesting... with your code I have one dump as you, I guess something wrong with my code

[mattthhh]

If I put an error in inherit function of the class App as compose or on_mount I have also one dump, but when I put an error in a function of my subclass of App, here I have 2 dumps. Maybe I should reimplement all _fatal_error function in my subclass without using super()

[mattthhh]

Found a workaround with this :

self._exit_renderables = [self._exit_renderables[0]]

with keeping super. Normally I should have no more than one errors to crash the entire app.