cpython-uasyncio: uasyncio compatibility module for CPython.

Implements scheduling a coroutine by yielding it.

Related discussion:
https://groups.google.com/d/msg/python-tulip/emU4_qyPVQM/eS8G0bnmBIEJ

cpython-uasyncio/example_yield_coro.py

@@ -0,0 +1,21 @@
+import uasyncio as asyncio
+
+
+def run1():
+    for i in range(1):
+        print('Hello World')
+        yield from asyncio.sleep(2)
+    print("run1 finished")
+
+def run2():
+    for i in range(3):
+        print('bar')
+        yield run1()
+        yield from asyncio.sleep(1)
+
+
+import logging
+logging.basicConfig(level=logging.INFO)
+loop = asyncio.get_event_loop()
+loop.create_task(run2())
+loop.run_forever()

cpython-uasyncio/metadata.txt

@@ -0,0 +1,3 @@
+srctype = cpython-backport
+type = module
+version = 0.1

cpython-uasyncio/patch.diff

@@ -0,0 +1,27 @@
+This patch shows changes done to asyncio.tasks.Task._step() from CPython 3.4.2.
+
+--- tasks.py	2015-01-01 10:51:40.707114866 +0200
++++ uasyncio.py	2015-01-01 10:54:20.172402890 +0200
+@@ -46,13 +55,16 @@
+                 # Bare yield relinquishes control for one event loop iteration.
+                 self._loop.call_soon(self._step)
+             elif inspect.isgenerator(result):
++                #print("Scheduling", result)
++                self._loop.create_task(result)
++                self._loop.call_soon(self._step)
+                 # Yielding a generator is just wrong.
+-                self._loop.call_soon(
+-                    self._step, None,
+-                    RuntimeError(
+-                        'yield was used instead of yield from for '
+-                        'generator in task {!r} with {}'.format(
+-                            self, result)))
++#                self._loop.call_soon(
++#                    self._step, None,
++#                    RuntimeError(
++#                        'yield was used instead of yield from for '
++#                        'generator in task {!r} with {}'.format(
++#                            self, result)))
+             else:
+                 # Yielding something else is an error.
+                 self._loop.call_soon(

cpython-uasyncio/setup.py

@@ -0,0 +1,18 @@
+import sys
+# Remove current dir from sys.path, otherwise setuptools will peek up our
+# module instead of system.
+sys.path.pop(0)
+from setuptools import setup
+
+
+setup(name='micropython-cpython-uasyncio',
+      version='0.1',
+      description='MicroPython module uasyncio ported to CPython',
+      long_description='This is MicroPython compatibility module, allowing applications using\nMicroPython-specific features to run on CPython.\n',
+      url='https://github.com/micropython/micropython/issues/405',
+      author='MicroPython Developers',
+      author_email='micro-python@googlegroups.com',
+      maintainer='MicroPython Developers',
+      maintainer_email='micro-python@googlegroups.com',
+      license='Python',
+      py_modules=['uasyncio'])

cpython-uasyncio/uasyncio.py

@@ -0,0 +1,80 @@
+import inspect
+import asyncio
+import asyncio.futures as futures
+from asyncio import *
+
+
+OrgTask = Task
+
+class Task(OrgTask):
+
+    def _step(self, value=None, exc=None):
+        assert not self.done(), \
+            '_step(): already done: {!r}, {!r}, {!r}'.format(self, value, exc)
+        if self._must_cancel:
+            if not isinstance(exc, futures.CancelledError):
+                exc = futures.CancelledError()
+            self._must_cancel = False
+        coro = self._coro
+        self._fut_waiter = None
+
+        self.__class__._current_tasks[self._loop] = self
+        # Call either coro.throw(exc) or coro.send(value).
+        try:
+            if exc is not None:
+                result = coro.throw(exc)
+            elif value is not None:
+                result = coro.send(value)
+            else:
+                result = next(coro)
+        except StopIteration as exc:
+            self.set_result(exc.value)
+        except futures.CancelledError as exc:
+            super().cancel()  # I.e., Future.cancel(self).
+        except Exception as exc:
+            self.set_exception(exc)
+        except BaseException as exc:
+            self.set_exception(exc)
+            raise
+        else:
+            if isinstance(result, futures.Future):
+                # Yielded Future must come from Future.__iter__().
+                if result._blocking:
+                    result._blocking = False
+                    result.add_done_callback(self._wakeup)
+                    self._fut_waiter = result
+                    if self._must_cancel:
+                        if self._fut_waiter.cancel():
+                            self._must_cancel = False
+                else:
+                    self._loop.call_soon(
+                        self._step, None,
+                        RuntimeError(
+                            'yield was used instead of yield from '
+                            'in task {!r} with {!r}'.format(self, result)))
+            elif result is None:
+                # Bare yield relinquishes control for one event loop iteration.
+                self._loop.call_soon(self._step)
+            elif inspect.isgenerator(result):
+                #print("Scheduling", result)
+                self._loop.create_task(result)
+                self._loop.call_soon(self._step)
+                # Yielding a generator is just wrong.
+#                self._loop.call_soon(
+#                    self._step, None,
+#                    RuntimeError(
+#                        'yield was used instead of yield from for '
+#                        'generator in task {!r} with {}'.format(
+#                            self, result)))
+            else:
+                # Yielding something else is an error.
+                self._loop.call_soon(
+                    self._step, None,
+                    RuntimeError(
+                        'Task got bad yield: {!r}'.format(result)))
+        finally:
+            self.__class__._current_tasks.pop(self._loop)
+            self = None  # Needed to break cycles when an exception occurs.
+
+
+asyncio.tasks.Task = Task