Add WIP example of silent IPC breaks while streaming

examples/open_ctx_w_nursery.py

@@ -0,0 +1,96 @@
+import trio
+from tractor import (
+    open_nursery,
+    context,
+    Context,
+    MsgStream,
+)
+
+
+async def break_channel_silently(
+    stream: MsgStream,
+):
+    async for msg in stream:
+        await stream.send(msg)
+        # XXX: close the channel right after an error is raised
+        # purposely breaking the IPC transport to make sure the parent
+        # doesn't get stuck in debug. this more or less simulates an
+        # infinite msg-receive hang on the other end. await
+        await stream._ctx.chan.send(None)
+        assert 0
+
+
+async def error_and_break_stream(
+    stream: MsgStream,
+):
+    async for msg in stream:
+        # echo back msg
+        await stream.send(msg)
+
+        try:
+            assert 0
+        except Exception:
+            await stream._ctx.chan.send(None)
+
+            # NOTE: doing this instead causes the error to propagate
+            # correctly.
+            # await stream.aclose()
+            raise
+
+
+@context
+async def just_sleep(
+
+    ctx: Context,
+    **kwargs,
+
+) -> None:
+    '''
+    Start and sleep.
+
+    '''
+    d = {}
+    await ctx.started()
+    try:
+        async with (
+            ctx.open_stream() as stream,
+            trio.open_nursery() as n,
+        ):
+            for i in range(100):
+                await stream.send(i)
+                if i > 50:
+                    n.start_soon(break_channel_silently, stream)
+                    n.start_soon(error_and_break_stream, stream)
+
+    finally:
+        d['10'] = 10
+
+
+async def main() -> None:
+
+    async with open_nursery(
+        # loglevel='info',
+        debug_mode=True,
+    ) as n:
+        portal = await n.start_actor(
+            'ctx_child',
+
+            # XXX: we don't enable the current module in order
+            # to trigger `ModuleNotFound`.
+            enable_modules=[__name__],
+
+            # add a debugger test to verify this works B)
+            # debug_mode=True,
+        )
+
+        async with portal.open_context(
+            just_sleep,  # taken from pytest parameterization
+        ) as (ctx, sent):
+            async with ctx.open_stream() as stream:
+                await stream.send(10)
+                async for msg in stream:
+                    print(msg)
+
+
+if __name__ == '__main__':
+    trio.run(main)