Fix #874

Refactor test__backdoor.py to be simpler, and add a test case for this
specific issue. Take the proposed patch of switch in by overriding
throw() just for backdoor because I don't really see a general place for
it in the hub.

changelog.rst

@@ -140,6 +140,9 @@ Other Changes
 - The various ``FileObject`` implementations are more consistent with
   each other. **Note:** Writing to the *io* property of a FileObject should be
   considered deprecated.
+- Timeout exceptions (and other asynchronous exceptions) could cause
+  the Backdoor server to fail to properly manage the
+  stdout/stderr/stdin values. Reported with a patch in :pr:`874` by stefanmh.
 
 Servers
 ~~~~~~~

src/gevent/backdoor.py

@@ -28,7 +28,6 @@ try:
 except AttributeError:
     sys.ps2 = '... '
 
-
 class _Greenlet_stdreplace(Greenlet):
     # A greenlet that replaces sys.std[in/out/err] while running.
     _fileobj = None
@@ -37,7 +36,7 @@ class _Greenlet_stdreplace(Greenlet):
     def switch(self, *args, **kw):
         if self._fileobj is not None:
             self.switch_in()
-        Greenlet.switch(self, *args, **kw) # pylint:disable=no-member
+        Greenlet.switch(self, *args, **kw)
 
     def switch_in(self):
         self.saved = sys.stdin, sys.stderr, sys.stdout
@@ -47,11 +46,16 @@ class _Greenlet_stdreplace(Greenlet):
         sys.stdin, sys.stderr, sys.stdout = self.saved
         self.saved = None
 
+    def throw(self, *args, **kwargs):
+        if self.saved is None and self._fileobj is not None:
+            self.switch_in()
+        Greenlet.throw(self, *args, **kwargs)
+
     def run(self):
         try:
             return Greenlet.run(self)
         finally:
-            # XXX why is this necessary?
+            # Make sure to restore the originals.
             self.switch_out()
 
 

src/greentest/greentest.py

@@ -367,8 +367,9 @@ class TestCase(TestCaseMetaClass("NewBase", (BaseTestCase,), {})):
             self.cleanup()
         self._error = self._none
         for x in self.close_on_teardown:
+            close = getattr(x, 'close', x)
             try:
-                x.close()
+                close()
             except Exception:
                 pass
         try:

src/greentest/test__backdoor.py

@@ -7,39 +7,45 @@ from _six import xrange
 
 def read_until(conn, postfix):
     read = b''
-    if isinstance(postfix, str) and str != bytes:
+    if not isinstance(postfix, bytes):
         postfix = postfix.encode('utf-8')
     while not read.endswith(postfix):
         result = conn.recv(1)
         if not result:
             raise AssertionError('Connection ended before %r. Data read:\n%r' % (postfix, read))
         read += result
-    if str != bytes:
-        read = read.decode('utf-8')
-    return read
 
+    return read if isinstance(read, str) else read.decode('utf-8')
 
-def create_connection(address):
-    conn = socket.socket()
-    conn.connect(address)
-    return conn
+def readline(conn):
+    with conn.makefile() as f:
+        return f.readline()
 
+class Test(greentest.TestCase):
 
-def readline(conn):
-    f = conn.makefile()
-    line = f.readline()
-    f.close()
-    return line
+    _server = None
 
+    def tearDown(self):
+        self._server.stop()
+        self._server = None
+        super(Test, self).tearDown()
 
-class Test(greentest.TestCase):
+    def _make_server(self, *args, **kwargs):
+        self._server = backdoor.BackdoorServer(('127.0.0.1', 0), *args, **kwargs)
+        self._close_on_teardown(self._server.stop)
+        self._server.start()
+
+    def _create_connection(self):
+        conn = socket.socket()
+        self._close_on_teardown(conn)
+        conn.connect(('127.0.0.1', self._server.server_port))
+        return conn
 
     def test(self):
-        server = backdoor.BackdoorServer(('127.0.0.1', 0))
-        server.start()
+        self._make_server()
 
         def connect():
-            conn = create_connection(('127.0.0.1', server.server_port))
+            conn = self._create_connection()
             try:
                 read_until(conn, '>>> ')
                 conn.sendall(b'2+2\r\n')
@@ -48,70 +54,66 @@ class Test(greentest.TestCase):
             finally:
                 conn.close()
 
-        try:
-            jobs = [gevent.spawn(connect) for _ in xrange(10)]
-            gevent.joinall(jobs, raise_error=True)
-        finally:
-            server.close()
-        #self.assertEqual(conn.recv(1), '')
+        jobs = [gevent.spawn(connect) for _ in xrange(10)]
+        gevent.joinall(jobs, raise_error=True)
 
     def test_quit(self):
-        server = backdoor.BackdoorServer(('127.0.0.1', 0))
-        server.start()
-        conn = None
-        try:
-            conn = create_connection(('127.0.0.1', server.server_port))
-            read_until(conn, '>>> ')
-            conn.sendall(b'quit()\r\n')
-            line = readline(conn)
-            self.assertEqual(line, '')
-        finally:
-            if conn is not None:
-                conn.close()
-            server.stop()
+        self._make_server()
+        conn = self._create_connection()
+        read_until(conn, '>>> ')
+        conn.sendall(b'quit()\r\n')
+        line = readline(conn)
+        self.assertEqual(line, '')
 
     def test_sys_exit(self):
-        server = backdoor.BackdoorServer(('127.0.0.1', 0))
-        server.start()
-        conn = None
-        try:
-            conn = create_connection(('127.0.0.1', server.server_port))
-            read_until(conn, b'>>> ')
-            conn.sendall(b'import sys; sys.exit(0)\r\n')
-            line = readline(conn)
-            self.assertEqual(line, '')
-        finally:
-            if conn is not None:
-                conn.close()
-            server.stop()
+        self._make_server()
+        conn = self._create_connection()
+        read_until(conn, b'>>> ')
+        conn.sendall(b'import sys; sys.exit(0)\r\n')
+        line = readline(conn)
+        self.assertEqual(line, '')
 
     def test_banner(self):
         banner = "Welcome stranger!" # native string
-        server = backdoor.BackdoorServer(('127.0.0.1', 0), banner=banner)
-        server.start()
-        try:
-            conn = create_connection(('127.0.0.1', server.server_port))
-            response = read_until(conn, b'>>> ')
-            self.assertEqual(response[:len(banner)], banner, response)
-            conn.close()
-        finally:
-            server.stop()
+        self._make_server(banner=banner)
+        conn = self._create_connection()
+        response = read_until(conn, b'>>> ')
+        self.assertEqual(response[:len(banner)], banner, response)
 
     def test_builtins(self):
-        server = backdoor.BackdoorServer(('127.0.0.1', 0))
-        server.start()
-        conn = None
-        try:
-            conn = create_connection(('127.0.0.1', server.server_port))
-            read_until(conn, b'>>> ')
-            conn.sendall(b'locals()["__builtins__"]\r\n')
-            response = read_until(conn, '>>> ')
-            self.assertTrue(len(response) < 300, msg="locals() unusable: %s..." % response)
-        finally:
-            if conn is not None:
-                conn.close()
-            server.stop()
-
+        self._make_server()
+        conn = self._create_connection()
+        read_until(conn, b'>>> ')
+        conn.sendall(b'locals()["__builtins__"]\r\n')
+        response = read_until(conn, '>>> ')
+        self.assertTrue(len(response) < 300, msg="locals() unusable: %s..." % response)
+
+    def test_switch_exc(self):
+        from gevent.queue import Queue, Empty
+
+        def bad():
+            q = Queue()
+            print('switching out, then throwing in')
+            try:
+                q.get(block=True, timeout=0.1)
+            except Empty:
+                print("Got Empty")
+            print('switching out')
+            gevent.sleep(0.1)
+            print('switched in')
+
+        self._make_server(locals={'bad': bad})
+        conn = self._create_connection()
+        read_until(conn, b'>>> ')
+        conn.sendall(b'bad()\r\n')
+        response = read_until(conn, '>>> ')
+        response = response.replace('\r\n', '\n')
+        self.assertEqual('switching out, then throwing in\nGot Empty\nswitching out\nswitched in\n>>> ', response)
+
+        conn.sendall(b'quit()\r\n')
+        line = readline(conn)
+        self.assertEqual(line, '')
+        conn.close()
 
 if __name__ == '__main__':
     greentest.main()