feat: drop cachetools dependency in favor of simple local implementation

Author: akx

.kokoro/requirements.txt

@@ -16,10 +16,6 @@ backports-tarfile==1.2.0 \
     --hash=sha256:77e284d754527b01fb1e6fa8a1afe577858ebe4e9dad8919e34c862cb399bc34 \
     --hash=sha256:d75e02c268746e1b8144c278978b6e98e85de6ad16f8e4b0844a154557eca991
     # via jaraco-context
-cachetools==5.5.0 \
-    --hash=sha256:02134e8439cdc2ffb62023ce1debca2944c3f289d66bb17ead3ab3dede74b292 \
-    --hash=sha256:2cc24fb4cbe39633fb7badd9db9ca6295d766d9c2995f245725a46715d050f2a
-    # via google-auth
 certifi==2024.8.30 \
     --hash=sha256:922820b53db7a7257ffbda3f597266d435245903d80737e34f8a45ff3e3230d8 \
     --hash=sha256:bec941d2aa8195e248a60b31ff9f0558284cf01a52591ceda73ea9afffd69fd9

google/auth/_cache.py

@@ -0,0 +1,42 @@
+from collections import OrderedDict
+
+
+class LRUCache(dict):
+    def __init__(self, maxsize):
+        super().__init__()
+        self._order = OrderedDict()
+        self.maxsize = maxsize
+
+    def clear(self):
+        super().clear()
+        self._order.clear()
+
+    def __getitem__(self, key):
+        value = super().__getitem__(key)
+        self._update(key)
+        return value
+
+    def __setitem__(self, key, value):
+        maxsize = self.maxsize
+        if maxsize <= 0:
+            return
+        if key not in self:
+            while len(self) >= maxsize:
+                self.popitem()
+        super().__setitem__(key, value)
+        self._update(key)
+
+    def __delitem__(self, key):
+        super().__delitem__(key)
+        del self._order[key]
+
+    def popitem(self):
+        """Remove and return the least recently used key-value pair."""
+        key, _ = self._order.popitem(last=False)
+        return key, super().pop(key)
+
+    def _update(self, key):
+        try:
+            self._order.move_to_end(key)
+        except KeyError:
+            self._order[key] = None

google/auth/jwt.py

@@ -50,8 +50,7 @@
 import json
 import urllib
 
-import cachetools
-
+from google.auth import _cache
 from google.auth import _helpers
 from google.auth import _service_account_info
 from google.auth import crypt
@@ -629,7 +628,7 @@ def __init__(
             token_lifetime (int): The amount of time in seconds for
                 which the token is valid. Defaults to 1 hour.
             max_cache_size (int): The maximum number of JWT tokens to keep in
-                cache. Tokens are cached using :class:`cachetools.LRUCache`.
+                cache. Tokens are cached using :class:`google.auth._cache.LRUCache`.
             quota_project_id (Optional[str]): The project ID used for quota
                 and billing.
 
@@ -645,7 +644,7 @@ def __init__(
             additional_claims = {}
 
         self._additional_claims = additional_claims
-        self._cache = cachetools.LRUCache(maxsize=max_cache_size)
+        self._cache = _cache.LRUCache(maxsize=max_cache_size)
 
     @classmethod
     def _from_signer_and_info(cls, signer, info, **kwargs):

noxfile.py

@@ -73,7 +73,6 @@ def mypy(session):
     session.install("-e", ".")
     session.install(
         "mypy",
-        "types-cachetools",
         "types-certifi",
         "types-freezegun",
         "types-pyOpenSSL",

setup.py

@@ -20,7 +20,6 @@
 
 
 DEPENDENCIES = (
-    "cachetools>=2.0.0,<6.0",
     "pyasn1-modules>=0.2.1",
     # rsa==4.5 is the last version to support 2.7
     # https://github.com/sybrenstuvel/python-rsa/issues/152#issuecomment-643470233

testing/constraints-3.7.txt

@@ -5,7 +5,6 @@
 #
 # e.g., if setup.py has "foo >= 1.14.0, < 2.0.0dev",
 # Then this file should have foo==1.14.0
-cachetools==2.0.0
 pyasn1-modules==0.2.1
 setuptools==40.3.0
 rsa==3.1.4

tests/test__cache.py

@@ -0,0 +1,22 @@
+from google.auth._cache import LRUCache
+
+
+def test_lru_cache():
+    lru_cache = LRUCache(2)
+    lru_cache["a"] = 1
+    lru_cache["b"] = 2
+    assert lru_cache["a"] == 1
+    lru_cache["c"] = 3
+    assert "b" not in lru_cache
+    assert lru_cache["a"] == 1
+    assert lru_cache["c"] == 3
+    lru_cache["d"] = 4
+    assert "a" not in lru_cache
+    assert lru_cache["c"] == 3
+    assert lru_cache["d"] == 4
+
+
+def test_zero_size_lru_cache():
+    lru_cache = LRUCache(0)
+    lru_cache["a"] = 1
+    assert "a" not in lru_cache