Validate throttle capacity and refill period before initialization

diskcache/recipes.py

@@ -266,6 +266,9 @@ def throttle(
     Assumes keys will not be evicted. Set the eviction policy to 'none' on the
     cache to guarantee the keys are not evicted.
 
+    The token capacity `count` must be finite and at least one. The refill
+    period `seconds` must be finite and greater than zero.
+
     >>> import diskcache, time
     >>> cache = diskcache.Cache()
     >>> count = 0
@@ -282,6 +285,10 @@ def throttle(
     """
 
     def decorator(func):
+        if not math.isfinite(count) or count < 1:
+            raise ValueError('count must be finite and at least one')
+        if not math.isfinite(seconds) or seconds <= 0:
+            raise ValueError('seconds must be finite and greater than zero')
         rate = count / float(seconds)
         key = full_name(func) if name is None else name
         now = time_func()

tests/test_recipes.py

@@ -104,3 +104,23 @@ def worker(num):
     while (time.time() - start) < 1:
         worker(100)
     assert state['num'] > 0
+
+
+@pytest.mark.parametrize('count', [0, -1, 0.5, float('nan'), float('inf')])
+def test_throttle_rejects_invalid_capacity(cache, count):
+    with pytest.raises(ValueError, match='count'):
+        dc.throttle(cache, count, 1, name='invalid')(lambda: None)
+    assert 'invalid' not in cache
+
+
+@pytest.mark.parametrize('seconds', [0, -1, float('nan'), float('inf')])
+def test_throttle_rejects_invalid_period(cache, seconds):
+    with pytest.raises(ValueError, match='seconds'):
+        dc.throttle(cache, 1, seconds, name='invalid')(lambda: None)
+    assert 'invalid' not in cache
+
+
+@pytest.mark.parametrize('count, seconds', [(1, 0.25), (1.5, 2), (2, 1)])
+def test_throttle_valid_capacity_and_period(cache, count, seconds):
+    function = dc.throttle(cache, count, seconds)(lambda: 'result')
+    assert function() == 'result'