fix issue #138: gevent.pool.Pool().imap_unordered hangs with an empty iterator (Thanks to exproxus)

gevent/pool.py

@@ -228,9 +228,13 @@ class IMapUnordered(Greenlet):
     def _run(self):
         try:
             func = self.func
+            empty = True
             for item in self.iterable:
                 self.count += 1
                 self.spawn(func, item).rawlink(self._on_result)
+                empty = False
+            if empty:
+                self.queue.put(Failure(StopIteration))
         finally:
             self.__dict__.pop('spawn', None)
             self.__dict__.pop('func', None)
@@ -288,6 +292,7 @@ class IMap(Greenlet):
 
     def _run(self):
         try:
+            empty = True
             func = self.func
             for item in self.iterable:
                 self.count += 1
@@ -295,6 +300,10 @@ class IMap(Greenlet):
                 g.rawlink(self._on_result)
                 self.maxindex += 1
                 g.index = self.maxindex
+                empty = False
+            if empty:
+                self.maxindex += 1
+                self.queue.put((self.maxindex, Failure(StopIteration)))
         finally:
             self.__dict__.pop('spawn', None)
             self.__dict__.pop('func', None)