Implement subprocess.run()

Make it available to all Python versions, not just 3.5. It is
cooperative on all versions.

This requires some minor updates to the Popen API (being a context
manager and having the args attribute on Python 2) and works best when
the TimeoutExpired exception is also defined in Python 2 (as a subclass
of Timeout, for BWC).

This prompts me to wonder if some of the duplicated Py2/Py3
methods (like check_call) can be combined now. I think I'm generally OK
with API extensions so long as there are no BWC concerns, and the
context-management, in particular, is nice for those methods.

Fixes #872.

changelog.rst

@@ -161,6 +161,17 @@ Other Changes
             considered deprecated after it is constructed.
 - The :func:`gevent.os.waitpid` function is cooperative in more
   circumstances. Reported in :issue:`878` by Heungsub Lee.
+- The :mod:`gevent.subprocess` module now provides the
+  :func:`gevent.subprocess.run` function in a cooperative way even
+  when the system is not monkey patched, on all supported versions of
+  Python. (It was added officially in Python 3.5.)
+- Popen objects can be used as context managers even on Python 2.
+- Popen objects save their *args* attribute even on Python 2.
+- :exc:`gevent.subprocess.TimeoutExpired` is defined even on Python 2,
+  where it is a subclass of the :exc:`gevent.timeout.Timeout`
+  exception; all instances where a ``Timeout`` exception would
+  previously be thrown under Python 2 will now throw a
+  ``TimeoutExpired`` exception.
 
 1.1.2 (Jul 21, 2016)
 ====================

src/gevent/timeout.py

@@ -124,11 +124,11 @@ class Timeout(BaseException):
        Add warning about negative *seconds* values.
     """
 
-    def __init__(self, seconds=None, exception=None, ref=True, priority=-1):
+    def __init__(self, seconds=None, exception=None, ref=True, priority=-1, _use_timer=True):
         BaseException.__init__(self)
         self.seconds = seconds
         self.exception = exception
-        if seconds is None:
+        if seconds is None or not _use_timer:
             # Avoid going through the timer codepath if no timeout is
             # desired; this avoids some CFFI interactions on PyPy that can lead to a
             # RuntimeError if this implementation is used during an `import` statement. See

src/greentest/test__subprocess.py

@@ -6,6 +6,7 @@ import gevent
 from gevent import subprocess
 import time
 import gc
+import tempfile
 
 
 PYPY = hasattr(sys, 'pypy_version_info')
@@ -229,5 +230,106 @@ class Test(greentest.TestCase):
 
         test_subprocess_in_native_thread.ignore_leakcheck = True
 
+class RunFuncTestCase(greentest.TestCase):
+    # Based on code from python 3.6
+
+    __timeout__ = 6
+
+    def run_python(self, code, **kwargs):
+        """Run Python code in a subprocess using subprocess.run"""
+        argv = [sys.executable, "-c", code]
+        return subprocess.run(argv, **kwargs)
+
+    def test_returncode(self):
+        # call() function with sequence argument
+        cp = self.run_python("import sys; sys.exit(47)")
+        self.assertEqual(cp.returncode, 47)
+        with self.assertRaises(subprocess.CalledProcessError):
+            cp.check_returncode()
+
+    def test_check(self):
+        with self.assertRaises(subprocess.CalledProcessError) as c:
+            self.run_python("import sys; sys.exit(47)", check=True)
+        self.assertEqual(c.exception.returncode, 47)
+
+    def test_check_zero(self):
+        # check_returncode shouldn't raise when returncode is zero
+        cp = self.run_python("import sys; sys.exit(0)", check=True)
+        self.assertEqual(cp.returncode, 0)
+
+    def test_timeout(self):
+        # run() function with timeout argument; we want to test that the child
+        # process gets killed when the timeout expires.  If the child isn't
+        # killed, this call will deadlock since subprocess.run waits for the
+        # child.
+        with self.assertRaises(subprocess.TimeoutExpired):
+            self.run_python("while True: pass", timeout=0.0001)
+
+    def test_capture_stdout(self):
+        # capture stdout with zero return code
+        cp = self.run_python("print('BDFL')", stdout=subprocess.PIPE)
+        self.assertIn(b'BDFL', cp.stdout)
+
+    def test_capture_stderr(self):
+        cp = self.run_python("import sys; sys.stderr.write('BDFL')",
+                             stderr=subprocess.PIPE)
+        self.assertIn(b'BDFL', cp.stderr)
+
+    def test_check_output_stdin_arg(self):
+        # run() can be called with stdin set to a file
+        tf = tempfile.TemporaryFile()
+        self.addCleanup(tf.close)
+        tf.write(b'pear')
+        tf.seek(0)
+        cp = self.run_python(
+            "import sys; sys.stdout.write(sys.stdin.read().upper())",
+            stdin=tf, stdout=subprocess.PIPE)
+        self.assertIn(b'PEAR', cp.stdout)
+
+    def test_check_output_input_arg(self):
+        # check_output() can be called with input set to a string
+        cp = self.run_python(
+            "import sys; sys.stdout.write(sys.stdin.read().upper())",
+            input=b'pear', stdout=subprocess.PIPE)
+        self.assertIn(b'PEAR', cp.stdout)
+
+    def test_check_output_stdin_with_input_arg(self):
+        # run() refuses to accept 'stdin' with 'input'
+        tf = tempfile.TemporaryFile()
+        self.addCleanup(tf.close)
+        tf.write(b'pear')
+        tf.seek(0)
+        with self.assertRaises(ValueError,
+                               msg="Expected ValueError when stdin and input args supplied.") as c:
+            self.run_python("print('will not be run')",
+                            stdin=tf, input=b'hare')
+        self.assertIn('stdin', c.exception.args[0])
+        self.assertIn('input', c.exception.args[0])
+
+    def test_check_output_timeout(self):
+        with self.assertRaises(subprocess.TimeoutExpired) as c:
+            self.run_python(
+                (
+                    "import sys, time\n"
+                    "sys.stdout.write('BDFL')\n"
+                    "sys.stdout.flush()\n"
+                    "time.sleep(3600)"
+                ),
+                # Some heavily loaded buildbots (sparc Debian 3.x) require
+                # this much time to start and print.
+                timeout=3, stdout=subprocess.PIPE)
+        self.assertEqual(c.exception.output, b'BDFL')
+        # output is aliased to stdout
+        self.assertEqual(c.exception.stdout, b'BDFL')
+
+    def test_run_kwargs(self):
+        newenv = os.environ.copy()
+        newenv["FRUIT"] = "banana"
+        cp = self.run_python(('import sys, os;'
+                              'sys.exit(33 if os.getenv("FRUIT")=="banana" else 31)'),
+                             env=newenv)
+        self.assertEqual(cp.returncode, 33)
+
+
 if __name__ == '__main__':
     greentest.main()