Unnecessary linebreak on 3.10-style Union types.

[kthy]

Describe the style change

Black 22.8.0 makes typing hints in Python ≥ 3.10 harder to read by line breaking on the pipe (type union) operator without any apparent reason.

Examples in the current Black style

I'm writing a FastAPI application:

from fastapi import APIRouter, Query

router = APIRouter(prefix="/black", tags=["black"])


@router.get("/foo")
async def foo(
    param1: str
    | None = Query(
        default=None, title="A parameter", description="A longer description of the parameter."
    ),
    param2: str
    | None = Query(
        default=None,
        title="Another parameter",
        description="A longer description of the other parameter.",
    ),
) -> str:
    """Docstring goes here."""
    return f"{param1=} {param2=}"

Desired style

from fastapi import APIRouter, Query

router = APIRouter(prefix="/pfx", tags=["pfx"])


@router.get("/foo")
async def foo(
    param1: str | None = Query(
        default=None, title="A parameter", description="A longer description of the parameter."
    ),
    param2: str | None = Query(
        default=None,
        title="Another parameter",
        description="A longer description of the other parameter.",
    ),
) -> str:
    """Docstring goes here."""
    return f"{param1=} {param2=}"

Additional context

If you remove the | None part of the typing hint, a linebreak is not inserted by Black.

str | None for types is syntax introduced in Python 3.10. Python 3.9 and earlier had Union[str, None] which is not susceptible to the problem.

[calumy]

This seems similar to #3296 which is a duplicate of #2316.

[kthy]

Thanks, I'd tried to search for existing issues but came up blank. Closing as dupe.