Issue #20400: Merge Tulip into Python: add the new asyncio.subprocess module

* Add a new asyncio.subprocess module
* Add new create_subprocess_exec() and create_subprocess_shell() functions
* The new asyncio.subprocess.SubprocessStreamProtocol creates stream readers
  for stdout and stderr and a stream writer for stdin.
* The new asyncio.subprocess.Process class offers an API close to the
  subprocess.Popen class:

  - pid, returncode, stdin, stdout and stderr attributes
  - communicate(), wait(), send_signal(), terminate() and kill() methods

* Remove STDIN (0), STDOUT (1) and STDERR (2) constants from base_subprocess
  and unix_events, to not be confused with the symbols with the same name of
  subprocess and asyncio.subprocess modules
* _ProactorBasePipeTransport.get_write_buffer_size() now counts also the size
  of the pending write
* _ProactorBaseWritePipeTransport._loop_writing() may now pause the protocol if
  the write buffer size is greater than the high water mark (64 KB by default)

Lib/test/test_asyncio/test_base_events.py

@@ -116,18 +116,17 @@ class BaseEventLoopTests(unittest.TestCase):
             self.loop.stop()
 
         self.loop._process_events = unittest.mock.Mock()
-        delay = 0.1
-
-        when = self.loop.time() + delay
+        when = self.loop.time() + 0.1
         self.loop.call_at(when, cb)
         t0 = self.loop.time()
         self.loop.run_forever()
         dt = self.loop.time() - t0
-
-        self.assertGreaterEqual(dt, delay - self.loop._granularity, dt)
-        # tolerate a difference of +800 ms because some Python buildbots
-        # are really slow
-        self.assertLessEqual(dt, 0.9, dt)
+        self.assertTrue(0.09 <= dt <= 0.9,
+                        # Issue #20452: add more info in case of failure,
+                        # to try to investigate the bug
+                        (dt,
+                         self.loop._granularity,
+                         time.get_clock_info('monotonic')))
 
     def test_run_once_in_executor_handle(self):
         def cb():

Lib/test/test_asyncio/test_events.py

@@ -1179,14 +1179,6 @@ class EventLoopTestsMixin:
         calls.append(self.loop._run_once_counter)
         self.assertEqual(calls, [1, 3, 5, 6])
 
-    def test_granularity(self):
-        granularity = self.loop._granularity
-        self.assertGreater(granularity, 0.0)
-        # Worst expected granularity: 1 ms on Linux (limited by poll/epoll
-        # resolution), 15.6 ms on Windows (limited by time.monotonic
-        # resolution)
-        self.assertLess(granularity, 0.050)
-
 
 class SubprocessTestsMixin:
 

Lib/test/test_asyncio/test_subprocess.py

@@ -0,0 +1,196 @@
+from asyncio import subprocess
+import asyncio
+import signal
+import sys
+import unittest
+from test import support
+if sys.platform != 'win32':
+    from asyncio import unix_events
+
+# Program exiting quickly
+PROGRAM_EXIT_FAST = [sys.executable, '-c', 'pass']
+
+# Program blocking
+PROGRAM_BLOCKED = [sys.executable, '-c', 'import time; time.sleep(3600)']
+
+# Program sleeping during 1 second
+PROGRAM_SLEEP_1SEC = [sys.executable, '-c', 'import time; time.sleep(1)']
+
+# Program copying input to output
+PROGRAM_CAT = [
+    sys.executable, '-c',
+    ';'.join(('import sys',
+              'data = sys.stdin.buffer.read()',
+              'sys.stdout.buffer.write(data)'))]
+
+class SubprocessMixin:
+    def test_stdin_stdout(self):
+        args = PROGRAM_CAT
+
+        @asyncio.coroutine
+        def run(data):
+            proc = yield from asyncio.create_subprocess_exec(
+                                          *args,
+                                          stdin=subprocess.PIPE,
+                                          stdout=subprocess.PIPE,
+                                          loop=self.loop)
+
+            # feed data
+            proc.stdin.write(data)
+            yield from proc.stdin.drain()
+            proc.stdin.close()
+
+            # get output and exitcode
+            data = yield from proc.stdout.read()
+            exitcode = yield from proc.wait()
+            return (exitcode, data)
+
+        task = run(b'some data')
+        task = asyncio.wait_for(task, 10.0, loop=self.loop)
+        exitcode, stdout = self.loop.run_until_complete(task)
+        self.assertEqual(exitcode, 0)
+        self.assertEqual(stdout, b'some data')
+
+    def test_communicate(self):
+        args = PROGRAM_CAT
+
+        @asyncio.coroutine
+        def run(data):
+            proc = yield from asyncio.create_subprocess_exec(
+                                          *args,
+                                          stdin=subprocess.PIPE,
+                                          stdout=subprocess.PIPE,
+                                          loop=self.loop)
+            stdout, stderr = yield from proc.communicate(data)
+            return proc.returncode, stdout
+
+        task = run(b'some data')
+        task = asyncio.wait_for(task, 10.0, loop=self.loop)
+        exitcode, stdout = self.loop.run_until_complete(task)
+        self.assertEqual(exitcode, 0)
+        self.assertEqual(stdout, b'some data')
+
+    def test_shell(self):
+        create = asyncio.create_subprocess_shell('exit 7',
+                                                 loop=self.loop)
+        proc = self.loop.run_until_complete(create)
+        exitcode = self.loop.run_until_complete(proc.wait())
+        self.assertEqual(exitcode, 7)
+
+    def test_start_new_session(self):
+        # start the new process in a new session
+        create = asyncio.create_subprocess_shell('exit 8',
+                                                 start_new_session=True,
+                                                 loop=self.loop)
+        proc = self.loop.run_until_complete(create)
+        exitcode = self.loop.run_until_complete(proc.wait())
+        self.assertEqual(exitcode, 8)
+
+    def test_kill(self):
+        args = PROGRAM_BLOCKED
+        create = asyncio.create_subprocess_exec(*args, loop=self.loop)
+        proc = self.loop.run_until_complete(create)
+        proc.kill()
+        returncode = self.loop.run_until_complete(proc.wait())
+        if sys.platform == 'win32':
+            self.assertIsInstance(returncode, int)
+            # expect 1 but sometimes get 0
+        else:
+            self.assertEqual(-signal.SIGKILL, returncode)
+
+    def test_terminate(self):
+        args = PROGRAM_BLOCKED
+        create = asyncio.create_subprocess_exec(*args, loop=self.loop)
+        proc = self.loop.run_until_complete(create)
+        proc.terminate()
+        returncode = self.loop.run_until_complete(proc.wait())
+        if sys.platform == 'win32':
+            self.assertIsInstance(returncode, int)
+            # expect 1 but sometimes get 0
+        else:
+            self.assertEqual(-signal.SIGTERM, returncode)
+
+    @unittest.skipIf(sys.platform == 'win32', "Don't have SIGHUP")
+    def test_send_signal(self):
+        args = PROGRAM_BLOCKED
+        create = asyncio.create_subprocess_exec(*args, loop=self.loop)
+        proc = self.loop.run_until_complete(create)
+        proc.send_signal(signal.SIGHUP)
+        returncode = self.loop.run_until_complete(proc.wait())
+        self.assertEqual(-signal.SIGHUP, returncode)
+
+    def test_get_subprocess(self):
+        args = PROGRAM_EXIT_FAST
+
+        @asyncio.coroutine
+        def run():
+            proc = yield from asyncio.create_subprocess_exec(*args,
+                                                             loop=self.loop)
+            yield from proc.wait()
+
+            popen = proc.get_subprocess()
+            popen.wait()
+            return (proc, popen)
+
+        proc, popen = self.loop.run_until_complete(run())
+        self.assertEqual(popen.returncode, proc.returncode)
+        self.assertEqual(popen.pid, proc.pid)
+
+    def test_broken_pipe(self):
+        large_data = b'x' * support.PIPE_MAX_SIZE
+
+        create = asyncio.create_subprocess_exec(
+                             *PROGRAM_SLEEP_1SEC,
+                             stdin=subprocess.PIPE,
+                             loop=self.loop)
+        proc = self.loop.run_until_complete(create)
+        with self.assertRaises(BrokenPipeError):
+            self.loop.run_until_complete(proc.communicate(large_data))
+        self.loop.run_until_complete(proc.wait())
+
+
+if sys.platform != 'win32':
+    # Unix
+    class SubprocessWatcherMixin(SubprocessMixin):
+        Watcher = None
+
+        def setUp(self):
+            policy = asyncio.get_event_loop_policy()
+            self.loop = policy.new_event_loop()
+
+            # ensure that the event loop is passed explicitly in the code
+            policy.set_event_loop(None)
+
+            watcher = self.Watcher()
+            watcher.attach_loop(self.loop)
+            policy.set_child_watcher(watcher)
+
+        def tearDown(self):
+            policy = asyncio.get_event_loop_policy()
+            policy.set_child_watcher(None)
+            self.loop.close()
+            policy.set_event_loop(None)
+
+    class SubprocessSafeWatcherTests(SubprocessWatcherMixin, unittest.TestCase):
+        Watcher = unix_events.SafeChildWatcher
+
+    class SubprocessFastWatcherTests(SubprocessWatcherMixin, unittest.TestCase):
+        Watcher = unix_events.FastChildWatcher
+else:
+    # Windows
+    class SubprocessProactorTests(SubprocessMixin, unittest.TestCase):
+        def setUp(self):
+            policy = asyncio.get_event_loop_policy()
+            self.loop = asyncio.ProactorEventLoop()
+
+            # ensure that the event loop is passed explicitly in the code
+            policy.set_event_loop(None)
+
+        def tearDown(self):
+            policy = asyncio.get_event_loop_policy()
+            self.loop.close()
+            policy.set_event_loop(None)
+
+
+if __name__ == '__main__':
+    unittest.main()

Lib/test/test_asyncio/test_windows_events.py

@@ -105,7 +105,7 @@ class ProactorTests(unittest.TestCase):
         self.loop.run_until_complete(f)
         elapsed = self.loop.time() - start
         self.assertFalse(f.result())
-        self.assertTrue(0.18 < elapsed < 0.9, elapsed)
+        self.assertTrue(0.18 < elapsed < 0.5, elapsed)
 
         _overlapped.SetEvent(event)