Merge pull request python-hyper#39 from python-hyper/issue-38

Allow exclusive dependency on stream 0 (as None).

Author: Lukasa

HISTORY.rst

@@ -1,6 +1,14 @@
 Changelog
 =========
 
+dev
+---
+
+**Bugfixes**
+
+- Allow ``insert_stream`` to be called with ``exclusive=True`` but no explicit
+  ``depends_on`` value.
+
 1.2.1 (2016-10-26)
 ------------------
 

src/priority/priority.py

@@ -286,16 +286,15 @@ def insert_stream(self,
 
         stream = Stream(stream_id, weight)
 
+        if not depends_on:
+            depends_on = 0
+
         if exclusive:
-            assert depends_on is not None
             parent_stream = self._get_or_insert_parent(depends_on)
             self._exclusive_insert(parent_stream, stream)
             self._streams[stream_id] = stream
             return
 
-        if not depends_on:
-            depends_on = 0
-
         parent = self._get_or_insert_parent(depends_on)
         parent.add_child(stream)
         self._streams[stream_id] = stream

test/test_priority.py

@@ -235,6 +235,10 @@ def test_priority_tree_raises_deadlock_error_if_all_blocked(self):
             (7,  1,    True,  16, [1],    [7, 3, 7, 3, 7, 3, 7, 3, 7]),
             (7,  1,    True,  16, [1, 7], [5, 3, 11, 3, 5, 3, 11, 3, 5]),
             (1,  0,    False, 32, [],     [1, 3, 7, 1, 7, 1, 3, 7, 1]),
+            (1,  0,    True,  32, [],     [1, 1, 1, 1, 1, 1, 1, 1, 1]),
+            (1,  0,    True,  32, [1],    [3, 5, 7, 7, 3, 5, 7, 7, 3]),
+            (1,  None, True,  32, [],     [1, 1, 1, 1, 1, 1, 1, 1, 1]),
+            (1,  None, True,  32, [1],    [3, 5, 7, 7, 3, 5, 7, 7, 3]),
         ]
     )
     def test_can_reprioritize_a_stream(self,
@@ -371,6 +375,22 @@ def test_priority_refuses_to_allow_too_many_streams_in_tree(self, count):
         with pytest.raises(priority.TooManyStreamsError):
             p.insert_stream(x + 1)
 
+    @pytest.mark.parametrize('depends_on', [0, None])
+    def test_can_insert_stream_with_exclusive_dependency_on_0(self,
+                                                              depends_on):
+        """
+        It is acceptable to insert a stream with an exclusive dependency on
+        stream 0, both explicitly and implicitly.
+        """
+        p = priority.PriorityTree()
+        p.insert_stream(stream_id=1)
+        p.insert_stream(stream_id=3)
+
+        p.insert_stream(stream_id=5, depends_on=depends_on, exclusive=True)
+
+        next_ten_ids = [next(p) for _ in range(0, 10)]
+        assert next_ten_ids == [5] * 10
+
 
 class TestPriorityTreeOutput(object):
     """