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fix(cache): preserve LRUDict.get defaults and LRU order #8683

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fix(cache): preserve LRUDict.get defaults and LRU order #8683

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6 changes: 3 additions & 3 deletions aws_lambda_powertools/shared/cache_dict.py
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Original file line number Diff line number Diff line change
Expand Up @@ -3,8 +3,8 @@

class LRUDict(OrderedDict):
"""
Cache implementation based on ordered dict with a maximum number of items. Last accessed item will be evicted
first. Currently used by idempotency utility.
Cache implementation based on ordered dict with a maximum number of items. Least recently used item will be
evicted first. Currently used by idempotency utility.
"""

def __init__(self, max_items=1024, *args, **kwargs):
Expand All @@ -26,6 +26,6 @@ def __setitem__(self, key, value):

def get(self, key, *args, **kwargs):
item = super().get(key, *args, **kwargs)
if item:
if key in self:
self.move_to_end(key=key)
return item
20 changes: 20 additions & 0 deletions tests/unit/test_lru_cache.py
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Original file line number Diff line number Diff line change
Expand Up @@ -43,6 +43,26 @@ def test_cache_order_get(populated_cache):
assert last_item == f"key_{random_value}"


def test_cache_get_missing_key_returns_default():
cache = LRUDict(max_items=2)
cache["existing"] = "value"

assert cache.get("missing", "fallback") == "fallback"
assert list(cache) == ["existing"]


@pytest.mark.parametrize("value", [False, 0, None, ""])
def test_cache_get_falsey_value_updates_recency(value):
cache = LRUDict(max_items=2)
cache["falsey"] = value
cache["other"] = "value"

assert cache.get("falsey") == value
cache["new"] = "value"

assert list(cache) == ["falsey", "new"]


def test_cache_evict_over_max_items(populated_cache):
assert "key_0" in populated_cache
assert len(populated_cache) == MAX_CACHE_ITEMS
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