The compiler is not picky right now, but these are actually all syntax
errors:
- await is only valid in an async function
- async functions that use yield are actually async generators (a construct
not supported by the compiler right now)
This fixes the cases where the task being waited on finishes just before or
just after the wait_for itself is cancelled.
Fixes issue #8717.
Signed-off-by: Damien George <damien@micropython.org>
These are internal names and can be safely renamed without affecting user
code. push_sorted() and push_head() are merged into a single push()
method, which is already how the C version is implemented. pop_head() is
simply renamed to pop().
The changes are:
- q.push_sorted(task, t) -> q.push(task, t)
- q.push_head(task) -> q.push(task)
- q.pop_head() -> q.pop()
The shorter names and removal of push_head() leads to a code size reduction
of between 40 and 64 bytes on bare-metal targets.
Signed-off-by: Damien George <damien@micropython.org>
This fixes a bug where the gather is cancelled externally and then one of
its sub-tasks (that the gather was waiting on) finishes right between the
cancellation being queued and being executed.
Signed-off-by: Damien George <damien@micropython.org>
The following fixes are made:
- cancelling a gather now cancels all sub-tasks of the gather (previously
it would only cancel the first)
- if any sub-task of a gather raises an exception then the gather finishes
(previously it would only finish if the first sub-task raised)
Fixes issues #5798, #7807, #7901.
Signed-off-by: Damien George <damien@micropython.org>
This commit switches the roles of the helper task from a cancellation task
to a runner task, to get the correct semantics for cancellation of
wait_for.
Some uasyncio tests are now disabled for the native emitter due to issues
with native code generation of generators and yield-from.
Fixes#5797.
Signed-off-by: Damien George <damien@micropython.org>
When a tasks raises an exception which is uncaught, and no other task
await's on that task, then an error message is printed (or a user function
called) via a call to Loop.call_exception_handler. In CPython this call is
made when the Task object is freed (eg via reference counting) because it's
at that point that it is known that the exception that was raised will
never be handled.
MicroPython does not have reference counting and the current behaviour is
to deal with uncaught exceptions as early as possible, ie as soon as they
terminate the task. But this can be undesirable because in certain cases
a task can start and raise an exception immediately (before any await is
executed in that task's coro) and before any other task gets a chance to
await on it to catch the exception.
This commit changes the behaviour so that tasks which end due to an
uncaught exception are scheduled one more time for execution, and if they
are not await'ed on by the next scheduling loop, then the exception handler
is called (eg the exception is printed out).
Signed-off-by: Damien George <damien@micropython.org>
This commit adds a completely new implementation of the uasyncio module.
The aim of this version (compared to the original one in micropython-lib)
is to be more compatible with CPython's asyncio module, so that one can
more easily write code that runs under both MicroPython and CPython (and
reuse CPython asyncio libraries, follow CPython asyncio tutorials, etc).
Async code is not easy to write and any knowledge users already have from
CPython asyncio should transfer to uasyncio without effort, and vice versa.
The implementation here attempts to provide good compatibility with
CPython's asyncio while still being "micro" enough to run where MicroPython
runs. This follows the general philosophy of MicroPython itself, to make it
feel like Python.
The main change is to use a Task object for each coroutine. This allows
more flexibility to queue tasks in various places, eg the main run loop,
tasks waiting on events, locks or other tasks. It no longer requires
pre-allocating a fixed queue size for the main run loop.
A pairing heap is used to queue Tasks.
It's currently implemented in pure Python, separated into components with
lazy importing for optional components. In the future parts of this
implementation can be moved to C to improve speed and reduce memory usage.
But the aim is to maintain a pure-Python version as a reference version.
