fix: add .get() to LRUCache

Co-authored-by: Aarni Koskela <akx@iki.fi>

Author: chalmerlowe

google/auth/_cache.py

@@ -1,3 +1,17 @@
+# Copyright 2025 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
 from collections import OrderedDict
 
 
@@ -11,6 +25,14 @@ def clear(self):
         super().clear()
         self._order.clear()
 
+    def get(self, key, default=None):
+        try:
+            value = super().__getitem__(key)
+            self._update(key)
+            return value
+        except KeyError:
+            return default
+
     def __getitem__(self, key):
         value = super().__getitem__(key)
         self._update(key)

tests/test__cache.py

@@ -2,6 +2,7 @@
 
 
 def test_lru_cache():
+    """Test the LRUCache for generally expected functionality and ordering."""
     lru_cache = LRUCache(2)
     lru_cache["a"] = 1
     lru_cache["b"] = 2
@@ -17,6 +18,31 @@ def test_lru_cache():
 
 
 def test_zero_size_lru_cache():
+    """Confirm the LRUCache handles zero-size correctly."""
     lru_cache = LRUCache(0)
     lru_cache["a"] = 1
     assert "a" not in lru_cache
+
+
+def test_lru_cache_get_updates_lru():
+    """Confirm the LRUCache handles get calls correctly."""
+    lru_cache = LRUCache(2)
+    lru_cache["a"] = 1
+    lru_cache["b"] = 2
+
+    # Access "a" via get(), making it MRU.
+    assert lru_cache.get("a") == 1
+
+    # Add "c", which should evict "b" (LRU), not "a".
+    lru_cache["c"] = 3
+
+    assert "a" in lru_cache
+    assert "b" not in lru_cache
+    assert "c" in lru_cache
+
+
+def test_lru_cache_get_missing():
+    """Confirm the LRUCache handles missing keys correctly."""
+    lru_cache = LRUCache(2)
+    assert lru_cache.get("missing") is None
+    assert lru_cache.get("missing", "default") == "default"