[WIP/RFC] allow polling on a provided fd

neovim/api/nvim.py

@@ -322,6 +322,20 @@ def new_highlight_source(self):
         """Return new src_id for use with Buffer.add_highlight."""
         return self.current.buffer.add_highlight("", 0, src_id=0)
 
+    def _error_wrapper(self, fn, call_point, *args, **kwargs):
+        if fn is None:
+            return None
+        def handler():
+            try:
+                fn(*args, **kwargs)
+            except Exception as err:
+                msg = ("error caught while executing async callback:\n"
+                       "{0!r}\n{1}\n \nthe call was requested at\n{2}"
+                       .format(err, format_exc_skip(1, 5), call_point))
+                self._err_cb(msg)
+                raise
+        return handler
+
     def async_call(self, fn, *args, **kwargs):
         """Schedule `fn` to be called by the event loop soon.
 
@@ -333,18 +347,33 @@ def async_call(self, fn, *args, **kwargs):
         that shouldn't block neovim.
         """
         call_point = ''.join(format_stack(None, 5)[:-1])
+        handler = self._error_wrapper(fn, call_point, *args, **kwargs)
 
-        def handler():
-            try:
-                fn(*args, **kwargs)
-            except Exception as err:
-                msg = ("error caught while executing async callback:\n"
-                       "{0!r}\n{1}\n \nthe call was requested at\n{2}"
-                       .format(err, format_exc_skip(1, 5), call_point))
-                self._err_cb(msg)
-                raise
         self._session.threadsafe_call(handler)
 
+    def poll_fd(self, fd, on_readable=None, on_writable=None, greenlet=True):
+        """
+        Invoke callbacks when the fd is ready for reading and/or writing. if
+        `on_readable` is not None, it should be callback, which will be invoked
+        (with no arguments) when the fd is ready for writing. Similarily if
+        `on_writable` is not None it will be invoked when the fd is ready for
+        writing.
+
+        Only one callback (of each kind) can be registered on the same fd at a
+        time. If both readability and writability should be monitored, both
+        callbacks must be registered by the same `poll_fd` call.
+
+        By default, the function is invoked in a greenlet, just like a callback
+        scheduled by async_call. 
+
+        Returns a function that deactivates the callback(s).
+        """
+        call_point = ''.join(format_stack(None, 5)[:-1])
+        on_readable = self._error_wrapper(on_readable, call_point)
+        on_writable = self._error_wrapper(on_writable, call_point)
+        return self._session.poll_fd(fd, on_readable, on_writable, greenlet)
+
+
 
 class Buffers(object):
 

neovim/msgpack_rpc/async_session.py

@@ -32,6 +32,10 @@ def threadsafe_call(self, fn):
         """Wrapper around `MsgpackStream.threadsafe_call`."""
         self._msgpack_stream.threadsafe_call(fn)
 
+    def poll_fd(self, fd, on_readable, on_writable):
+        """Wrapper around `BaseEventLoop.poll_fd`."""
+        return self._msgpack_stream.poll_fd(fd, on_readable, on_writable)
+
     def request(self, method, args, response_cb):
         """Send a msgpack-rpc request to Nvim.
 

neovim/msgpack_rpc/event_loop/asyncio.py

@@ -113,6 +113,18 @@ def _stop(self):
     def _threadsafe_call(self, fn):
         self._loop.call_soon_threadsafe(fn)
 
+    def _poll_fd(self, fd, on_readable, on_writable):
+        if on_readable is not None:
+            self._loop.add_reader(fd, on_readable)
+        if on_writable is not None:
+            self._loop.add_writer(fd, on_writable)
+        def cancel():
+            if on_readable is not None:
+                self._loop.remove_reader(fd)
+            if on_writable is not None:
+                self._loop.remove_writer(fd)
+        return cancel
+
     def _setup_signals(self, signals):
         if os.name == 'nt':
             # add_signal_handler is not supported in win32

neovim/msgpack_rpc/event_loop/base.py

@@ -121,6 +121,24 @@ def threadsafe_call(self, fn):
         """
         self._threadsafe_call(fn)
 
+    def poll_fd(self, fd, on_readable=None, on_writable=None):
+        """
+        Invoke callbacks when the fd is ready for reading and/or writing. if
+        `on_readable` is not None, it should be callback, which will be invoked
+        (with no arguments) when the fd is ready for writing. Similarily if
+        `on_writable` is not None it will be invoked when the fd is ready for
+        writing.
+
+        Only one callback (of each kind) can be registered on the same fd at a
+        time. If both readability and writability should be monitored, both
+        callbacks must be registered by the same `poll_fd` call.
+
+        Returns a function that deactivates the callback(s).
+        """
+        if on_readable is None and on_writable is None:
+            raise ValueError("poll_fd: At least one of `on_readable` and `on_writable` must be present")
+        return self._poll_fd(fd, on_readable, on_writable)
+
     def run(self, data_cb):
         """Run the event loop."""
         if self._error:

neovim/msgpack_rpc/event_loop/uv.py

@@ -106,6 +106,22 @@ def _on_async(self, handle):
         while self._callbacks:
             self._callbacks.popleft()()
 
+    def _poll_fd(self, fd, on_readable, on_writable):
+        poll = pyuv.Poll(self._loop, fd)
+        events = 0
+        if on_readable is not None:
+            events |= pyuv.UV_READABLE
+        if on_writable is not None:
+            events |= pyuv.UV_WRITABLE
+        def callback(poll_handle, evts, errorno):
+            if evts & pyuv.UV_READABLE:
+                on_readable()
+            if evts & pyuv.UV_WRITABLE:
+                on_writable()
+
+        poll.start(events, callback)
+        return poll.stop
+
     def _setup_signals(self, signals):
         self._signal_handles = []
 

neovim/msgpack_rpc/msgpack_stream.py

@@ -28,6 +28,10 @@ def threadsafe_call(self, fn):
         """Wrapper around `BaseEventLoop.threadsafe_call`."""
         self._event_loop.threadsafe_call(fn)
 
+    def poll_fd(self, fd, on_readable, on_writable):
+        """Wrapper around `BaseEventLoop.poll_fd`."""
+        return self._event_loop.poll_fd(fd, on_readable, on_writable)
+
     def send(self, msg):
         """Queue `msg` for sending to Nvim."""
         debug('sent %s', msg)

neovim/msgpack_rpc/session.py

@@ -28,8 +28,10 @@ def __init__(self, async_session):
         self._is_running = False
         self._setup_exception = None
 
-    def threadsafe_call(self, fn, *args, **kwargs):
-        """Wrapper around `AsyncSession.threadsafe_call`."""
+    def _wrap_greenlet(self, fn, *args, **kwargs):
+        if fn is None:
+            return None
+
         def handler():
             try:
                 fn(*args, **kwargs)
@@ -41,8 +43,23 @@ def greenlet_wrapper():
             gr = greenlet.greenlet(handler)
             gr.switch()
 
+        return greenlet_wrapper
+
+    def threadsafe_call(self, fn, *args, **kwargs):
+        """Wrapper around `AsyncSession.threadsafe_call`."""
+
+        greenlet_wrapper = self._wrap_greenlet(fn, *args, **kwargs)
         self._async_session.threadsafe_call(greenlet_wrapper)
 
+    def poll_fd(self, fd, on_readable, on_writable, greenlet=True):
+        """Wrapper around `AsyncSession.threadsafe_call`."""
+        if greenlet:
+            on_readable = self._wrap_greenlet(on_readable)
+            on_writable = self._wrap_greenlet(on_writable)
+
+        return self._async_session.poll_fd(fd, on_readable, on_writable)
+
+
     def next_message(self):
         """Block until a message(request or notification) is available.