JavaScript semantics are such that the caller of an async function does not
need to await that function for it to run to completion. This commit makes
that behaviour also apply to top-level async Python code run via
`runPythonAsync()`.
Signed-off-by: Damien George <damien@micropython.org>
The `reason` in a rejected promise should be an instance of `Error`. That
leads to better error messages on the JavaScript side.
Signed-off-by: Damien George <damien@micropython.org>
This commit adds a significant portion of the existing MicroPython asyncio
module to the webassembly port, using parts of the existing asyncio code
and some custom JavaScript parts.
The key difference to the standard asyncio is that this version uses the
JavaScript runtime to do the actual scheduling and waiting on events, eg
Promise fulfillment, timeouts, fetching URLs.
This implementation does not include asyncio.run(). Instead one just uses
asyncio.create_task(..) to start tasks and then returns to the JavaScript.
Then JavaScript will run the tasks.
The implementation here tries to reuse as much existing asyncio code as
possible, and gets all the semantics correct for things like cancellation
and asyncio.wait_for. An alternative approach would reimplement Task,
Event, etc using JavaScript Promise's. That approach is very difficult to
get right when trying to implement cancellation (because it's not possible
to cancel a JavaScript Promise).
Signed-off-by: Damien George <damien@micropython.org>
This optimises the case where a Python function is, for example, stored to
a JavaScript attribute and then later retrieved from Python. The Python
function no longer needs to be a proxy with double proxying needed for the
call from Python -> JavaScript -> Python.
Signed-off-by: Damien George <damien@micropython.org>
