Fixed #30759 -- Made cache.delete() return whether it succeeded.

Thanks Simon Charette for the review.

6 files changed, 22 insertions, 9 deletions

diff --git a/django/core/cache/backends/base.py b/django/core/cache/backends/base.py
index b3a65ab40f..cf9629bc03 100644
--- a/django/core/cache/backends/base.py
+++ b/django/core/cache/backends/base.py
@@ -132,7 +132,8 @@ class BaseCache:
 
     def delete(self, key, version=None):
         """
-        Delete a key from the cache, failing silently.
+        Delete a key from the cache and return whether it succeeded, failing
+        silently.
         """
         raise NotImplementedError('subclasses of BaseCache must provide a delete() method')
 
diff --git a/django/core/cache/backends/db.py b/django/core/cache/backends/db.py
index 17b5209659..33c79c5a14 100644
--- a/django/core/cache/backends/db.py
+++ b/django/core/cache/backends/db.py
@@ -197,7 +197,8 @@ class DatabaseCache(BaseDatabaseCache):
                 return True
 
     def delete(self, key, version=None):
-        self.delete_many([key], version)
+        self.validate_key(key)
+        return self._base_delete_many([self.make_key(key, version)])
 
     def delete_many(self, keys, version=None):
         key_list = []
@@ -208,7 +209,7 @@ class DatabaseCache(BaseDatabaseCache):
 
     def _base_delete_many(self, keys):
         if not keys:
-            return
+            return False
 
         db = router.db_for_write(self.cache_model_class)
         connection = connections[db]
@@ -224,6 +225,7 @@ class DatabaseCache(BaseDatabaseCache):
                 ),
                 keys,
             )
+        return bool(cursor.rowcount)
 
     def has_key(self, key, version=None):
         key = self.make_key(key, version=version)
diff --git a/django/core/cache/backends/dummy.py b/django/core/cache/backends/dummy.py
index 942b72ef89..3913746c49 100644
--- a/django/core/cache/backends/dummy.py
+++ b/django/core/cache/backends/dummy.py
@@ -28,6 +28,7 @@ class DummyCache(BaseCache):
     def delete(self, key, version=None):
         key = self.make_key(key, version=version)
         self.validate_key(key)
+        return False
 
     def has_key(self, key, version=None):
         key = self.make_key(key, version=version)
diff --git a/django/core/cache/backends/filebased.py b/django/core/cache/backends/filebased.py
index 48b8df90ab..3d76f0371b 100644
--- a/django/core/cache/backends/filebased.py
+++ b/django/core/cache/backends/filebased.py
@@ -76,16 +76,17 @@ class FileBasedCache(BaseCache):
             return False
 
     def delete(self, key, version=None):
-        self._delete(self._key_to_file(key, version))
+        return self._delete(self._key_to_file(key, version))
 
     def _delete(self, fname):
         if not fname.startswith(self._dir) or not os.path.exists(fname):
-            return
+            return False
         try:
             os.remove(fname)
         except FileNotFoundError:
             # The file may have been removed by another process.
-            pass
+            return False
+        return True
 
     def has_key(self, key, version=None):
         fname = self._key_to_file(key, version)
diff --git a/django/core/cache/backends/locmem.py b/django/core/cache/backends/locmem.py
index 6058bf5f7e..2573d14497 100644
--- a/django/core/cache/backends/locmem.py
+++ b/django/core/cache/backends/locmem.py
@@ -108,13 +108,14 @@ class LocMemCache(BaseCache):
             del self._cache[key]
             del self._expire_info[key]
         except KeyError:
-            pass
+            return False
+        return True
 
     def delete(self, key, version=None):
         key = self.make_key(key, version=version)
         self.validate_key(key)
         with self._lock:
-            self._delete(key)
+            return self._delete(key)
 
     def clear(self):
         with self._lock:
diff --git a/django/core/cache/backends/memcached.py b/django/core/cache/backends/memcached.py
index 48cfb8310b..8202005045 100644
--- a/django/core/cache/backends/memcached.py
+++ b/django/core/cache/backends/memcached.py
@@ -78,7 +78,7 @@ class BaseMemcachedCache(BaseCache):
 
     def delete(self, key, version=None):
         key = self.make_key(key, version=version)
-        self._cache.delete(key)
+        return bool(self._cache.delete(key))
 
     def get_many(self, keys, version=None):
         key_map = {self.make_key(key, version=version): key for key in keys}
@@ -170,6 +170,13 @@ class MemcachedCache(BaseMemcachedCache):
             return default
         return val
 
+    def delete(self, key, version=None):
+        # python-memcached's delete() returns True when key doesn't exist.
+        # https://github.com/linsomniac/python-memcached/issues/170
+        # Call _deletetouch() without the NOT_FOUND in expected results.
+        key = self.make_key(key, version=version)
+        return bool(self._cache._deletetouch([b'DELETED'], 'delete', key))
+
 
 class PyLibMCCache(BaseMemcachedCache):
     "An implementation of a cache binding using pylibmc"