snapshot of https://github.com/zulip/zulip.git @ 48c69911c7dd4e03b20552eb3bd77ad8151c1357 (2026-09-15)

zerver/lib/per_request_cache.py

@@ -0,0 +1,40 @@
+import functools
+from collections.abc import Callable, Hashable
+from typing import Any, TypeVar
+
+ReturnT = TypeVar("ReturnT")
+
+FUNCTION_NAME_TO_PER_REQUEST_RESULT: dict[str, dict[Any, Any]] = {}
+
+
+def cache_for_current_request(f: Callable[..., ReturnT]) -> Callable[..., ReturnT]:
+    """Cache the return value for each distinct set of arguments
+    during the current request.  Unlike
+    @cache_for_current_request, this supports functions
+    with any hashable arguments, not just a single int key."""
+    cache_key = f.__name__
+
+    assert cache_key not in FUNCTION_NAME_TO_PER_REQUEST_RESULT
+    FUNCTION_NAME_TO_PER_REQUEST_RESULT[cache_key] = {}
+
+    @functools.wraps(f)
+    def wrapper(*args: Hashable, **kwargs: Hashable) -> ReturnT:
+        cache = FUNCTION_NAME_TO_PER_REQUEST_RESULT[cache_key]
+        key = (args, frozenset(kwargs.items()))
+        if key in cache:
+            return cache[key]
+        result = f(*args, **kwargs)
+        cache[key] = result
+        return result
+
+    return wrapper
+
+
+def flush_per_request_cache(cache_key: str) -> None:
+    if cache_key in FUNCTION_NAME_TO_PER_REQUEST_RESULT:
+        FUNCTION_NAME_TO_PER_REQUEST_RESULT[cache_key] = {}
+
+
+def flush_per_request_caches() -> None:
+    for cache_key in FUNCTION_NAME_TO_PER_REQUEST_RESULT:
+        FUNCTION_NAME_TO_PER_REQUEST_RESULT[cache_key] = {}