Remove `keylen` from `LruCache`. (#9993)

`keylen` seems to be a thing that is frequently incorrectly set, and we don't really need it.

The only time it was used was to figure out if we had removed a subtree in `del_multi`, which we can do better by changing `TreeCache.pop` to return a different type (`TreeCacheNode`).

Commits should be independently reviewable.

1 files changed, 4 insertions, 2 deletions

diff --git a/tests/util/test_treecache.py b/tests/util/test_treecache.py
index 3b077af27e..6066372053 100644
--- a/tests/util/test_treecache.py
+++ b/tests/util/test_treecache.py
@@ -13,7 +13,7 @@
 # limitations under the License.
 
 
-from synapse.util.caches.treecache import TreeCache
+from synapse.util.caches.treecache import TreeCache, iterate_tree_cache_entry
 
 from .. import unittest
 
@@ -64,12 +64,14 @@ class TreeCacheTestCase(unittest.TestCase):
         cache[("a", "b")] = "AB"
         cache[("b", "a")] = "BA"
         self.assertEquals(cache.get(("a", "a")), "AA")
-        cache.pop(("a",))
+        popped = cache.pop(("a",))
         self.assertEquals(cache.get(("a", "a")), None)
         self.assertEquals(cache.get(("a", "b")), None)
         self.assertEquals(cache.get(("b", "a")), "BA")
         self.assertEquals(len(cache), 1)
 
+        self.assertEquals({"AA", "AB"}, set(iterate_tree_cache_entry(popped)))
+
     def test_clear(self):
         cache = TreeCache()
         cache[("a",)] = "A"