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

zerver/lib/profile.py

@@ -0,0 +1,38 @@
+import cProfile
+from collections.abc import Callable
+from functools import wraps
+from typing import TypeVar
+
+from typing_extensions import ParamSpec
+
+ParamT = ParamSpec("ParamT")
+ReturnT = TypeVar("ReturnT")
+
+
+def profiled(func: Callable[ParamT, ReturnT]) -> Callable[ParamT, ReturnT]:
+    """
+    This decorator should obviously be used only in a dev environment.
+    It works best when surrounding a function that you expect to be
+    called once.  One strategy is to write a backend test and wrap the
+    test case with the profiled decorator.
+
+    You can run a single test case like this:
+
+        # edit zerver/tests/test_external.py and place @profiled above the test case below
+        ./tools/test-backend zerver.tests.test_external.RateLimitTests.test_ratelimit_decrease
+
+    Then view the results like this:
+
+        ./tools/show-profile-results test_ratelimit_decrease.profile
+
+    """
+
+    @wraps(func)
+    def wrapped_func(*args: ParamT.args, **kwargs: ParamT.kwargs) -> ReturnT:
+        fn = func.__name__ + ".profile"
+        prof = cProfile.Profile()
+        retval = prof.runcall(func, *args, **kwargs)
+        prof.dump_stats(fn)
+        return retval
+
+    return wrapped_func