Support AnyIO

[davidbrochart]

@agronholm I know that you're working on the 5.0 branch, and you have probably been thinking about lots of things that I'm not even aware of, but I've been playing with this PR and the following example code, and it seems to work pretty well.
In #97 you seem to have taken another direction by treating tasks as resources, which is not what I do here, so I'm wondering what I am missing.

from anyio import run, sleep
from asphalt.core import ContainerComponent, Component, context_teardown, run_application

async def task0():
    print("task0 start")
    await sleep(2)
    print("task0 end")

async def task1():
    print("task1 start")
    await sleep(1)
    # 1 / 0
    await sleep(1)
    print("task1 end")

class Component1(Component):
    @context_teardown
    async def start(self, ctx):
        self.task_group.start_soon(task1)
        yield
        print("teardown1")

class Component0(ContainerComponent):
    @context_teardown
    async def start(self, ctx):
        self.add_component("component1", Component1)
        self.task_group.start_soon(task0)
        await sleep(1)
        await super().start(ctx)
        yield
        print("teardown0")

async def main():
    component0 = Component0()
    await run_application(component0, start_timeout=3)

run(main)

[agronholm]

Well, having the test suite pass would be a start :)
But seriously, I will take a look at this tomorrow or the day after. I'm pretty sure it's not very simple to move to structured concurrency or I would've done it long ago already.

[davidbrochart]

I'm pretty sure it's not very simple to move to structured concurrency or I would've done it long ago already.

I know, that's why I suspect I'm missing something 😄
I will work on tests if you think this PR is worth it.

[agronholm]

Meanwhile you can describe for me how you see the startup and shutdown sequences of nested components working with this approach.

[davidbrochart]

👍 will do but later, it's late here.

[davidbrochart]

The application starts with a top-level task group, that is passed to the root component, and that is used to start it with a timeout. Each ContainerComponent creates a new task group where it starts its child components, and this task group is also passed to the child components.
In the example above, the root component Component0 starts a task task0 using its component-level task group, and adds Component1 which starts task1 with its (nested) component-level task group. If no exception happens, the application runs until all tasks are done, then each component's teardown runs. If an exception happens (like in task1 by uncommenting 1 / 0), the application stops after running the teardowns, and the exception is finally raised.

[coveralls]

coverage: 96.39% (-1.0%) from 97.393%
when pulling e08eb00 on davidbrochart:anyio
into bac9743 on asphalt-framework:master.

[agronholm]

I'll take a closer look at this on the weekend. I really, really want structured concurrency in Asphalt ASAP.

[davidbrochart]

Closing in favor of #102.