Fix #643 by using the right methods in Queue.peek; add test cases.

changelog.rst

@@ -12,6 +12,8 @@
   enabled with ``-O`` or ``PYTHONOPTIMIZE``. Previously these would go
   undetected if optimizations were enabled, potentially leading to
   erratic, difficult to debug behaviour.
+- Fix an ``AttributeError`` from ``gevent.queue.Queue`` when ``peek``
+  was called on an empty ``Queue``. Reported in :issue:`643` by michaelvol.
 
 1.1b3 (Aug 16, 2015)
 ====================

gevent/queue.py

@@ -298,7 +298,7 @@ class Queue(object):
             waiter = Waiter()
             timeout = Timeout.start_new(timeout, Empty)
             try:
-                self.getters.add(waiter)
+                self.getters.append(waiter)
                 if self.putters:
                     self._schedule_unlock()
                 result = waiter.get()
@@ -306,7 +306,7 @@ class Queue(object):
                     raise InvalidSwitchError('Invalid switch into Queue.peek: %r' % (result, ))
                 return self._peek()
             finally:
-                self.getters.discard(waiter)
+                self.getters.remove(waiter)
                 timeout.cancel()
         else:
             raise Empty

greentest/test__queue.py

 from greentest import TestCase, main, GenericGetTestCase
 import gevent
-from gevent.hub import get_hub
+from gevent.hub import get_hub, LoopExit
 from gevent import util
 from gevent import queue
 from gevent.queue import Empty, Full
@@ -13,8 +13,20 @@ class TestQueue(TestCase):
         self.switch_expected = False
         q = queue.Queue()
         q.put('hi')
+        self.assertEquals(q.peek(), 'hi')
         self.assertEquals(q.get(), 'hi')
 
+    def test_peek_empty(self):
+        q = queue.Queue()
+        # No putters waiting, in the main loop: LoopExit
+        self.assertRaises(LoopExit, q.peek)
+
+        def waiter(q):
+            self.assertRaises(Empty, q.peek, timeout=0.01)
+        g = gevent.spawn(waiter, q)
+        gevent.sleep(0.1)
+        g.join()
+
     def test_send_last(self):
         q = queue.Queue()
 
@@ -68,7 +80,7 @@ class TestQueue(TestCase):
 
         p1 = gevent.spawn(sender, e1, q)
         gevent.sleep(0.001)
-        self.assert_(not e1.ready())
+        self.assertTrue(not e1.ready())
         p2 = gevent.spawn(receiver, e2, q)
         self.assertEquals(e2.get(), 'hi')
         self.assertEquals(e1.get(), 'done')