Issue #19018: The heapq.merge() function no longer suppresses IndexError
diff --git a/Lib/heapq.py b/Lib/heapq.py
index ca79db1..19037ab 100644
--- a/Lib/heapq.py
+++ b/Lib/heapq.py
@@ -366,6 +366,7 @@
'''
_heappop, _heapreplace, _StopIteration = heappop, heapreplace, StopIteration
+ _len = len
h = []
h_append = h.append
@@ -377,17 +378,21 @@
pass
heapify(h)
- while 1:
+ while _len(h) > 1:
try:
- while 1:
- v, itnum, next = s = h[0] # raises IndexError when h is empty
+ while True:
+ v, itnum, next = s = h[0]
yield v
s[0] = next() # raises StopIteration when exhausted
_heapreplace(h, s) # restore heap condition
except _StopIteration:
_heappop(h) # remove empty iterator
- except IndexError:
- return
+ if h:
+ # fast case when only a single iterator remains
+ v, itnum, next = h[0]
+ yield v
+ for v in next.__self__:
+ yield v
# Extend the implementations of nsmallest and nlargest to use a key= argument
_nsmallest = nsmallest
diff --git a/Lib/test/test_heapq.py b/Lib/test/test_heapq.py
index 73b88f0..c4de593 100644
--- a/Lib/test/test_heapq.py
+++ b/Lib/test/test_heapq.py
@@ -158,6 +158,15 @@
self.assertEqual(sorted(chain(*inputs)), list(self.module.merge(*inputs)))
self.assertEqual(list(self.module.merge()), [])
+ def test_merge_does_not_suppress_index_error(self):
+ # Issue 19018: Heapq.merge suppresses IndexError from user generator
+ def iterable():
+ s = list(range(10))
+ for i in range(20):
+ yield s[i] # IndexError when i > 10
+ with self.assertRaises(IndexError):
+ list(self.module.merge(iterable(), iterable()))
+
def test_merge_stability(self):
class Int(int):
pass