core-quality-py-async-without-await

Pack: core-quality Default severity: MAJOR Languages: Python Lifecycle: experimental Confidence: 0.85

What it catches

async def functions whose body contains no await expression, no async for, and no async with. Almost always a missing-await bug — the developer meant await something() and wrote something().

Async-protocol dunders are exempt by name: __aenter__, __aexit__, __aiter__, __anext__, __await__. They legitimately don't need an internal await — the protocol does the awaiting.

Why this matters for vibe-coded apps

A missing await is invisible at the call site: the coroutine returns a Coroutine object that nobody schedules, the side effect silently never happens, and FastAPI / asyncio carry on as if the work succeeded. Either add the missing await or drop the async keyword.

Example — flagged

async def fetch_user(id):
    user = lookup(id)         # ← missing await; flagged on the `async def`
    return user

async def cleanup():          # no await at all; flagged
    return 'done'

async def with_inner_await(): # inner function's await doesn't count
    async def nested():
        return await something()
    return nested

Example — not flagged

async def fetch_user(id):
    user = await lookup(id)        # explicit await — silent
    return user

async def for_await_loop(items):
    async for item in items:       # `async for` is an implicit await
        yield item

async def using_async_with():
    async with cm():               # `async with` is an implicit await
        return 'ok'

class Resource:
    async def __aenter__(self):    # async-protocol dunder — exempt
        return self

Suggested fix

# (a) Add the missing await.
async def fetch_user(id):
    user = await lookup(id)

# (b) Drop the async keyword — the body is synchronous.
def fetch_user(id):
    return lookup_sync(id)

Implementation

Tree-sitter-python AST. Visits every function_definition with an async modifier child. bodyHasAwait recursively walks the body for any await expression OR a for_statement / with_statement with an async child token. Nested function definitions are skipped (their awaits don't satisfy the outer's contract).

Source: `shared/packs/core-quality/core-quality-py-async-without-await.ts` Fixtures: `corpus/rules/core-quality-py-async-without-await/`