unused-async (RUF029)

This rule is unstable and in preview. The --preview flag is required for use.

What it does

Checks for functions declared async that do not await or otherwise use features requiring the function to be declared async.

Why is this bad?

Declaring a function async when it's not is usually a mistake, and will artificially limit the contexts where that function may be called. In some cases, labeling a function async is semantically meaningful (e.g. with the trio library).

Examples

async def foo():
    bar()

Use instead:

def foo():
    bar()