Propagate any spawned asyncio task error upwards

This should mostly maintain top level SC principles for any task spawned
using `tractor.to_asyncio.run()`. When the `asyncio` task completes make
sure to cancel the pertaining `trio` cancel scope and raise any error
that may have resulted.

Resolves #120

tractor/_entry.py

@@ -12,9 +12,6 @@
 from . import _state
 
 
-__all__ = ('run',)
-
-
 log = get_logger(__name__)
 
 

tractor/to_asyncio.py

@@ -13,30 +13,33 @@
 
 import trio
 
+from ._state import current_actor
+
+
+__all__ = ['run']
+
 
 async def _invoke(
-    from_trio,
-    to_trio,
-    coro
+    from_trio: trio.abc.ReceiveChannel,
+    to_trio: asyncio.Queue,
+    coro: Awaitable,
 ) -> Union[AsyncGenerator, Awaitable]:
     """Await or stream awaiable object based on type into
     ``trio`` memory channel.
     """
     async def stream_from_gen(c):
         async for item in c:
-            to_trio.put_nowait(item)
-        to_trio.put_nowait
+            to_trio.send_nowait(item)
 
     async def just_return(c):
-        to_trio.put_nowait(await c)
+        to_trio.send_nowait(await c)
 
     if inspect.isasyncgen(coro):
         return await stream_from_gen(coro)
     elif inspect.iscoroutine(coro):
         return await coro
 
 
-# TODO: make this some kind of tractor.to_asyncio.run()
 async def run(
     func: Callable,
     qsize: int = 2**10,
@@ -45,6 +48,8 @@ async def run(
     """Run an ``asyncio`` async function or generator in a task, return
     or stream the result back to ``trio``.
     """
+    assert current_actor()._infected_aio
+
     # ITC (inter task comms)
     from_trio = asyncio.Queue(qsize)
     to_trio, from_aio = trio.open_memory_channel(qsize)
@@ -55,16 +60,40 @@ async def run(
 
     coro = func(**kwargs)
 
+    cancel_scope = trio.CancelScope()
+
     # start the asyncio task we submitted from trio
     # TODO: try out ``anyio`` asyncio based tg here
-    asyncio.create_task(_invoke(from_trio, to_trio, coro))
+    task = asyncio.create_task(_invoke(from_trio, to_trio, coro))
+    err = None
+
+    # XXX: I'm not sure this actually does anything...
+    def cancel_trio(task):
+        """Cancel the calling ``trio`` task on error.
+        """
+        nonlocal err
+        err = task.exception()
+        cancel_scope.cancel()
+
+    task.add_done_callback(cancel_trio)
 
     # determine return type async func vs. gen
     if inspect.isasyncgen(coro):
-        await from_aio.get()
+        # simple async func
+        async def result():
+            with cancel_scope:
+                return await from_aio.get()
+            if cancel_scope.cancelled_caught and err:
+                raise err
+
     elif inspect.iscoroutine(coro):
-        async def gen():
-            async for tick in from_aio:
-                yield tuple(tick)
+        # asycn gen
+        async def result():
+            with cancel_scope:
+                async with from_aio:
+                    async for item in from_aio:
+                        yield item
+            if cancel_scope.cancelled_caught and err:
+                raise err
 
-        return gen()
+    return result()