Used a proper IntEnum class for the sqlite threading mode using for c…

…aching.

tiled/_tests/test_client_cache.py

@@ -11,7 +11,7 @@
 from ..adapters.array import ArrayAdapter
 from ..adapters.mapping import MapAdapter
 from ..client import Context, from_context, record_history
-from ..client.cache import Cache, CachedResponse, with_thread_lock
+from ..client.cache import Cache, CachedResponse, ThreadingMode, with_thread_lock
 from ..server.app import build_app
 
 tree = MapAdapter(
@@ -177,7 +177,7 @@ def test_clear_cache(client):
 
 def test_not_thread_safe(client, monkeypatch):
     # Check that writes fail if thread safety is disabled
-    monkeypatch.setattr(sqlite3, "threadsafety", 0)
+    monkeypatch.setattr(sqlite3, "threadsafety", ThreadingMode.SINGLE_THREAD)
     cache = client.context.cache
     # Clear the cache in another thread
     with concurrent.futures.ThreadPoolExecutor(max_workers=5) as executor:
@@ -187,7 +187,8 @@ def test_not_thread_safe(client, monkeypatch):
 
 
 @pytest.mark.skipif(
-    sqlite3.threadsafety < 2, reason="sqlite not built with thread safe support"
+    sqlite3.threadsafety != ThreadingMode.SERIALIZED,
+    reason="sqlite not built with thread safe support",
 )
 def test_thread_safety(client):
     cache = client.context.cache

tiled/client/cache.py

@@ -1,3 +1,4 @@
+import enum
 import json
 import os
 import sqlite3
@@ -162,6 +163,18 @@ def wrapper(obj, *args, **kwargs):
     return wrapper
 
 
+class ThreadingMode(enum.IntEnum):
+    """Threading mode used in the sqlite3 package.
+
+    https://docs.python.org/3/library/sqlite3.html#sqlite3.threadsafety
+
+    """
+
+    SINGLE_THREAD = 0
+    MULTI_THREAD = 1
+    SERIALIZED = 3
+
+
 class Cache:
     def __init__(
         self,
@@ -201,9 +214,8 @@ def write_safe(self):
         lock (``@with_thread_lock``) to prevent parallel writes.
 
         """
-        SERIALIZED = 3  # Could be defined in an enum elsewhere
         is_main_thread = threading.current_thread().ident == self._owner_thread
-        sqlite_is_safe = sqlite3.threadsafety == SERIALIZED
+        sqlite_is_safe = sqlite3.threadsafety == ThreadingMode.SERIALIZED
         return is_main_thread or sqlite_is_safe
 
     def __getstate__(self):