await inside f-string

When I tried cythonizing

async def abc():
    return "abc"


async def main():
    print(f"{await abc()}")

I got

Error compiling Cython file:
------------------------------------------------------------
...
async def abc():
    return "abc"


async def main():
    print(f"{await abc()}")
                   ^
------------------------------------------------------------

test.pyx:6:20: Expected ')', found 'abc'

I’m sure python can run it directly. It seems that cython won’t parse await inside f-string, and I have to split it into two lines now.

[scoder]

Sure. The parser is in Parsing.py, look for p_f_string_expr(), which parses the expressions. Check CPython’s Grammar file to see what kind of expression is allowed there, and compare it to what Cython’s parser expects. Make sure Cython’s parser uses a parse function that accepts await. For tests, I think we should finally have a separate Cython specific test for async-await, in addition to CPython’s own tests that we run. Create a new test file tests/run/async_await.pyx, implement a test coroutine function in there and give it a doctest that asserts the necessary behaviour. See https://github.com/cython/cython/wiki/HackerGuide#tests on how to run that test.

[scoder]

Implemented in #3070.