Add condition wrapper without cache_info.

Author: tkem

src/cachetools/_decorators.py

@@ -127,6 +127,38 @@ def cache_clear():
     return wrapper
 
 
+def _cached_cond(func, cache, key, cond):
+    pending = set()
+
+    def wrapper(*args, **kwargs):
+        k = key(*args, **kwargs)
+        with cond:
+            cond.wait_for(lambda: k not in pending)
+            try:
+                return cache[k]
+            except KeyError:
+                pending.add(k)
+        try:
+            v = func(*args, **kwargs)
+            with cond:
+                try:
+                    cache[k] = v
+                except ValueError:
+                    pass  # value too large
+                return v
+        finally:
+            with cond:
+                pending.remove(k)
+                cond.notify_all()
+
+    def cache_clear():
+        with cond:
+            cache.clear()
+
+    wrapper.cache_clear = cache_clear
+    return wrapper
+
+
 def _cached_locked(func, cache, key, lock):
     def wrapper(*args, **kwargs):
         k = key(*args, **kwargs)
@@ -192,6 +224,8 @@ def _cached_wrapper(func, cache, key, lock, info):
             wrapper = _uncached(func)
         elif lock is None:
             wrapper = _cached_unlocked(func, cache, key)
+        elif hasattr(lock, "wait_for") and hasattr(lock, "notify_all"):
+            wrapper = _cached_cond(func, cache, key, lock)
         else:
             wrapper = _cached_locked(func, cache, key, lock)
         wrapper.cache_info = None