During tests there may be deadlocks

[ofek]

What Operating System are you running on? Windows

In the following snippet if you uncomment the yielding of the Header the test will block:

from textual.app import App
from textual.screen import Screen
from textual.widgets import Footer, Header, Input


class MyScreen(Screen):
    def compose(self):
        # yield Header()
        yield Input()
        yield Footer()


class MyApp(App):
    def on_mount(self):
        self.install_screen(MyScreen(), 'myscreen')
        self.push_screen('myscreen')


async def test():
    app = MyApp()
    async with app.run_test():
        raise Exception('never raised')

        assert True

[ofek]

Another example:

from textual.app import App
from textual.containers import Container
from textual.screen import Screen
from textual.widget import Widget
from textual.widgets import Footer


class MyWidget(Widget):
    def compose(self):
        yield Footer()


class MyScreen(Screen):
    def compose(self):
        yield Container(MyWidget())


class MyApp(App):
    def on_mount(self):
        self.install_screen(MyScreen(), 'myscreen')
        self.push_screen('myscreen')


async def test():
    app = MyApp()
    async with app.run_test():
        raise Exception('never raised')

        assert True

[davep]

Installed as a unit test in Textual, the most minimal version of this I can get to hang (although I can Ctrl+C it) is this:

from textual.app import App
from textual.screen import Screen
from textual.widget import Widget


class MyWidget(Widget):

    def compose(self):
        yield Widget()


class MyScreen(Screen):

    def compose(self):
        yield MyWidget()


class MyApp(App):

    def on_mount(self):
        self.install_screen(MyScreen(), 'myscreen')
        self.push_screen('myscreen')


async def test_this():
    app = MyApp()
    async with app.run_test():
        raise Exception('never raised')
        assert True

If I make MyApp.on_mount async and await the installation and the push of the screen:

from textual.app import App
from textual.screen import Screen
from textual.widget import Widget


class MyWidget(Widget):

    def compose(self):
        yield Widget()


class MyScreen(Screen):

    def compose(self):
        yield MyWidget()


class MyApp(App):

    async def on_mount(self):
        await self.install_screen(MyScreen(), 'myscreen')
        await self.push_screen('myscreen')


async def test_this():
    app = MyApp()
    async with app.run_test():
        raise Exception('never raised')
        assert True

it runs to completion just fine.

[davep]

And, for the sake of completeness, just to be sure it's not some fluke and the screen isn't getting mounted but the pilot is ladning...

from textual.app import App
from textual.screen import Screen
from textual.widget import Widget


class MyWidget(Widget):

    def compose(self):
        yield Widget()


class MyScreen(Screen):

    def compose(self):
        yield MyWidget()


class MyApp(App):

    async def on_mount(self):
        await self.install_screen(MyScreen(), 'myscreen')
        await self.push_screen('myscreen')


async def test_this():
    app = MyApp()
    async with app.run_test() as pilot:
        assert pilot.app.screen is pilot.app.get_screen("myscreen")

That runs fine for me.

[github-actions]

Don't forget to star the repository!

Follow @textualizeio for Textual updates.