Fix ZUNIONSTORE nan-to-zero handling again

Real redis handles things differently for ZINTERSTORE versus ZUNIONSTORE
(see antirez/redis#3954), and dd10a73 fixed it for ZINTERSTORE but then
broken it for ZUNIONSTORE.

Author: bmerry

fakeredis/_server.py

@@ -2154,6 +2154,10 @@ def _zunioninter(self, func, dest, numkeys, *args):
         for s, w in sorted(zip(sets, weights), key=lambda x: len(x[0])):
             for member, score in s.items():
                 score *= w
+                # Redis only does this step for ZUNIONSTORE. See
+                # https://github.com/antirez/redis/issues/3954.
+                if func == 'ZUNIONSTORE' and math.isnan(score):
+                    score = 0.0
                 if member not in out_members:
                     continue
                 if member in out:

test_fakeredis.py

@@ -2619,6 +2619,14 @@ def test_zunionstore_weights(self):
                          [(b'one', 3), (b'two', 6), (b'four', 8)])
 
     def test_zunionstore_nan_to_zero(self):
+        self.zadd('foo', {'x': math.inf})
+        self.zadd('foo2', {'x': math.inf})
+        self.redis.zunionstore('bar', {'foo': 1.0, 'foo2': 0.0})
+        # This is different to test_zinterstore_nan_to_zero because of a quirk
+        # in redis. See https://github.com/antirez/redis/issues/3954.
+        self.assertEqual(self.redis.zscore('bar', 'x'), math.inf)
+
+    def test_zunionstore_nan_to_zero2(self):
         self.zadd('foo', {'zero': 0})
         self.zadd('foo2', {'one': 1})
         self.zadd('foo3', {'one': 1})
@@ -2701,6 +2709,12 @@ def test_zinterstore_nokey(self):
         with self.assertRaises(redis.ResponseError):
             self.redis.zinterstore('baz', [], aggregate='MAX')
 
+    def test_zinterstore_nan_to_zero(self):
+        self.zadd('foo', {'x': math.inf})
+        self.zadd('foo2', {'x': math.inf})
+        self.redis.zinterstore('bar', {'foo': 1.0, 'foo2': 0.0})
+        self.assertEqual(self.redis.zscore('bar', 'x'), 0.0)
+
     def test_zunionstore_nokey(self):
         with self.assertRaises(redis.ResponseError):
             self.redis.zunionstore('baz', [], aggregate='MAX')