From 9ca2c14cd8af9f7cadc957ecbba9de7a08256664 Mon Sep 17 00:00:00 2001
From: Aarni Koskela <akx@iki.fi>
Date: Mon, 26 Aug 2024 13:51:54 +0300
Subject: [PATCH] feat: drop `cachetools` dependency in favor of simple local
 implementation

---
 .kokoro/requirements.txt    |  4 ----
 google/auth/_cache.py       | 42 +++++++++++++++++++++++++++++++++++++
 google/auth/jwt.py          |  7 +++----
 noxfile.py                  |  1 -
 setup.py                    |  1 -
 testing/constraints-3.7.txt |  1 -
 tests/test__cache.py        | 22 +++++++++++++++++++
 7 files changed, 67 insertions(+), 11 deletions(-)
 create mode 100644 google/auth/_cache.py
 create mode 100644 tests/test__cache.py

diff --git a/.kokoro/requirements.txt b/.kokoro/requirements.txt
index 9622baf0b..264902dd5 100644
--- a/.kokoro/requirements.txt
+++ b/.kokoro/requirements.txt
@@ -16,10 +16,6 @@ backports-tarfile==1.2.0 \
     --hash=sha256:77e284d754527b01fb1e6fa8a1afe577858ebe4e9dad8919e34c862cb399bc34 \
     --hash=sha256:d75e02c268746e1b8144c278978b6e98e85de6ad16f8e4b0844a154557eca991
     # via jaraco-context
-cachetools==5.3.3 \
-    --hash=sha256:0abad1021d3f8325b2fc1d2e9c8b9c9d57b04c3932657a72465447332c24d945 \
-    --hash=sha256:ba29e2dfa0b8b556606f097407ed1aa62080ee108ab0dc5ec9d6a723a007d105
-    # via google-auth
 certifi==2024.7.4 \
     --hash=sha256:5a1e7645bc0ec61a09e26c36f6106dd4cf40c6db3a1fb6352b0244e7fb057c7b \
     --hash=sha256:c198e21b1289c2ab85ee4e67bb4b4ef3ead0892059901a8d5b622f24a1101e90
diff --git a/google/auth/_cache.py b/google/auth/_cache.py
new file mode 100644
index 000000000..f03480230
--- /dev/null
+++ b/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
diff --git a/google/auth/jwt.py b/google/auth/jwt.py
index 1ebd565d4..3225d9e2e 100644
--- a/google/auth/jwt.py
+++ b/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):
diff --git a/noxfile.py b/noxfile.py
index 07cef9bcc..e3c8951cb 100644
--- a/noxfile.py
+++ b/noxfile.py
@@ -73,7 +73,6 @@ def mypy(session):
     session.install("-e", ".")
     session.install(
         "mypy",
-        "types-cachetools",
         "types-certifi",
         "types-freezegun",
         "types-pyOpenSSL",
diff --git a/setup.py b/setup.py
index 4e4c0d47b..70ac90cd6 100644
--- a/setup.py
+++ b/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
diff --git a/testing/constraints-3.7.txt b/testing/constraints-3.7.txt
index 6c4dd2e8c..dec647cfd 100644
--- a/testing/constraints-3.7.txt
+++ b/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
diff --git a/tests/test__cache.py b/tests/test__cache.py
new file mode 100644
index 000000000..6ac9326fb
--- /dev/null
+++ b/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