"coroutine was never awaited": the async function you called without await, and where to find them all

verbatim errorRuntimeWarning: coroutine 'Database.save_event' was never awaited coroutine: Database.save_event() -> None RuntimeWarning: Enable tracemalloc to get the object allocation traceback

Problem

An event-tracking side effect in a FastAPI service silently stopped working:

RuntimeWarning: coroutine 'Database.save_event' was never awaited
  coroutine: Database.save_event() -> None
RuntimeWarning: Enable tracemalloc to get the object allocation traceback

No exception. The request returned 200. The event was just... not saved. The warning scrolled past in logs nobody read.

Root cause

Calling an async def function returns a coroutine object — it does not run anything. Without await, the coroutine is created and immediately garbage-collected, producing the warning and executing zero of its body. Ours:

def log_event(event):        # sync helper, called from an async handler
    db.save_event(event)     # async def — this line created, then dropped, a coroutine

The extra trap: this bug is invisible in tests if the test suite's event loop collects pending coroutines or the DB layer uses a mock that swallows the call. It surfaced only because production counts disagreed with our dashboards.

fix preview — first 1 of 2 lines (python), truncated:

async def log_event(event):
… 1 more line in the fix

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