Preserve file descriptor blocking mode in add_reader and add_writer

tests/test_sockets.py

@@ -1,4 +1,5 @@
 import asyncio
+import os
 import pickle
 import select
 import socket
@@ -14,6 +15,28 @@
 
 class _TestSockets:
 
+    def test_add_reader_writer_preserves_blocking_mode(self):
+        read_fd, write_fd = os.pipe()
+        try:
+            self.assertTrue(os.get_blocking(read_fd))
+            self.loop.add_reader(read_fd, lambda: None)
+            try:
+                self.assertTrue(os.get_blocking(read_fd))
+            finally:
+                self.loop.remove_reader(read_fd)
+            self.assertTrue(os.get_blocking(read_fd))
+
+            self.assertTrue(os.get_blocking(write_fd))
+            self.loop.add_writer(write_fd, lambda: None)
+            try:
+                self.assertTrue(os.get_blocking(write_fd))
+            finally:
+                self.loop.remove_writer(write_fd)
+            self.assertTrue(os.get_blocking(write_fd))
+        finally:
+            os.close(read_fd)
+            os.close(write_fd)
+
     async def recv_all(self, sock, nbytes):
         buf = b''
         while len(buf) < nbytes:

uvloop/handles/poll.pyx

@@ -1,7 +1,9 @@
 @cython.no_gc_clear
 cdef class UVPoll(UVHandle):
     cdef _init(self, Loop loop, int fd):
-        cdef int err
+        cdef:
+            int err
+            bint was_blocking = os_get_blocking(fd)
 
         self._start_init(loop)
 
@@ -18,6 +20,13 @@ cdef class UVPoll(UVHandle):
 
         self._finish_init()
 
+        if was_blocking:
+            try:
+                os_set_blocking(fd, True)
+            except BaseException:
+                self._close()
+                raise
+
         self.fd = fd
         self.reading_handle = None
         self.writing_handle = None

uvloop/includes/stdlib.pxi

@@ -104,6 +104,8 @@ cdef os_environ = os.environ
 cdef os_dup = os.dup
 cdef os_set_inheritable = os.set_inheritable
 cdef os_get_inheritable = os.get_inheritable
+cdef os_get_blocking = os.get_blocking
+cdef os_set_blocking = os.set_blocking
 cdef os_close = os.close
 cdef os_open = os.open
 cdef os_devnull = os.devnull