Remove 'Implicit Async', Don't Await runtime.run()

[JeffersGlass]

This removes the ability to write "implicitly scheduled coroutine" code in <py-script> tags, and requires users to use known asyncio methods to run coroutines, like ensure_future() or create_task(). It reverts from the use of Pyodide's runPythonAsync() to runPython().

Fixes #879. See discussion in that issue.

This PR has a completed todo list and is ready for review.

• Primary code changes
• Run typescript, py-unit tests
• Fix async integration tests
• Adjust examples to remove implicit coroutine scheduling
  • bokeh_interactive
  • numpy_canvas_fractals
  • say_hello (?)
  • webgl/raycaster
• Add page to docs explaining deprecation and new strategies, add link in UserError

---

To be clear, users still absolutely still have the ability to run code asynchronously. All of these still work:

<!-- Basic coroutine running using asyncio.ensure_future() -->
<py-script>
import asyncio

async def main():
    display("I see you shiver with anticip", target="rocky-horror-quote")
    asyncio.sleep(5)
    display("...pation", target="rocky-horror-quote")

asyncio.ensure_future(main())
</py-script>

<!-- Running a coroutine forever -->
<py-script>
from js import console
import asyncio
from datetime import datetime

async def clock():
  while True:
    display(datetime.now().strftime("%m/%d/%Y, %H:%M:%S"), target="clock-output", append=False)
    await asyncio.sleep(1)

asyncio.ensure_future(clock())
console.log("This is logged right away, even though the clock() coroutine runs forever")
</py-script>

<!-- Using asyncio.gather() to run many coroutines -->
<py-script>
import asyncio
import random

async def individual_counter(label, delay):
  local_count = 0
  while local_count <= 10:
    await asyncio.sleep(delay)
    console.log(f"{label}-{local_count}")
    local_count += 1

  console.log(f"{label} finished!")

labels = ["A", "B", "C", "D"]
asyncio.gather(*[individual_counter(label, random.random() + 1) for label in labels])
</py-script>

What this PR removes is the old "top-level await, implicit coroutine scheduling" style permitted by runPythonAsync:

<py-script>
import asyncio
display("First")
await asyncio.sleep(1)
display("second")
</py-script>

The above code now fails, and shows a UserError explaining why this code is no longer permitted:

[antocuni]

woooo 🎉🎉🎉

[JeffersGlass]

Interesting error in test_py_config: "DeprecationWarning: There is no current event loop'" shows up in the console, causing an assert to fail.

Some googling suggests this is related to deprecation of "asyncio.get_event_loop()". Will investigate.
pytest asyncio issue
Docs: asyncio.get_event_loop

[JeffersGlass]

I added docs explaining the deprecation of implicit coroutine scheduling; the added Asyncio/Await page in the docs could use some fleshing out, but I think that should be a separate PR.

[marimeireles]

Hey @JeffersGlass just to confirm. This is not a WIP anymore, right?
Maybe you can morph it into a "real" PR?

[JeffersGlass]

This is not a WIP anymore, right?

Whoops! You're correct - I've removed "WIP". Thanks!

I didn't see that pre-commit.ci is failing here (though passing locally) - let me see if I can rectify that.

Docs build upload is failing too... but that's just the upload, not the build, which I think is a known issue of AWS permissions not being present for other-users' branches?

[madhur-tandon]

Docs build upload is failing too... but that's just the upload, not the build, which I think is a known issue of AWS permissions not being present for other-users' branches?

Yes the AWS issue is known and can be ignored for now.

[marimeireles]

I'm a +1 thank you for your work here, this is great improvement! :)

[madhur-tandon]

Great PR!

[JeffersGlass]

Thanks y'all! I do want to give @antocuni a chance to weigh in here before I hit merge, since he's been deep into the lifecycle (and the issues await runtime.run() has been causing there).

[antocuni]

Very good and solid PR, I love it!
Goodbye implicit async ☠️ 👋 🔥
Left some minor comments, but I'm approving the PR already.

[JeffersGlass]

🚀

This breaks the brand new test_importmap from #938 in exactly the way explained there - because we await fetching importmaps (but with this PR no longer await runtime.run) not all importmaps may be loaded before run execute Python scripts. After talking with @antocuni, I've marked that test xfail for now.