Fix join after task-done with no get

Also shut down before put-join in shutdown-put-join tests. Also remove indent

Author: EpicWink

Lib/queue.py

@@ -241,7 +241,7 @@ def shutdown(self, immediate=False):
                 n_items = self._qsize()
                 while self._qsize():
                     self._get()
-                self.unfinished_tasks -= n_items
+                self.unfinished_tasks = max(self.unfinished_tasks - n_items, 0)
                 self.not_empty.notify_all()
                 # release all blocked threads in `join()`
                 self.all_tasks_done.notify_all()

Lib/test/test_queue.py

@@ -575,14 +575,13 @@ def _shutdown_put_join(self, immediate):
         for func, params in thrds:
             threads.append(threading.Thread(target=func, args=params))
             threads[-1].start()
-        if not immediate or immediate:  # TODO: dedent (minimising Git diff)
-            self.assertEqual(q.unfinished_tasks, nb)
-            for i in range(nb):
-                t = threading.Thread(target=q.task_done)
-                t.start()
-                threads.append(t)
-        go.set()
+        self.assertEqual(q.unfinished_tasks, nb)
+        for i in range(nb):
+            t = threading.Thread(target=q.task_done)
+            t.start()
+            threads.append(t)
         q.shutdown(immediate)
+        go.set()
         for t in threads:
             t.join()