Keep first argument on the same line for wrapped calls and literals

[vladkens]

Hi Ruff team 👋
First of all, thanks for Ruff — the formatter is excellent and we’ve been very happy with it overall.

I’d like to propose an optional formatting style for function calls and literals that improves compactness and readability in some cases.

Desired formatting

When a call or literal needs to be wrapped, keep the first argument (or opening literal) on the same line as the outer call:

items.append(WeeklyStats(
    period=period_name,
    volume=period_vol,
    fees=period_fee,
    realized_pnl=period_pnl,
))

items.append({
    "period_name": period_name,
    "volume": period_vol,
    "fees": period_fee,
    "realized_pnl": period_pnl,
})

Instead of the current default formatting:

items.append(
    WeeklyStats(
        period=period_name,
        volume=period_vol,
        fees=period_fee,
        realized_pnl=period_pnl,
    )
)

items.append(
    {
        "period_name": period_name,
        "volume": period_vol,
        "fees": period_fee,
        "realized_pnl": period_pnl,
    }
)

Motivation

This style:

• Reduces vertical space
• Makes the semantic grouping clearer (append(WeeklyStats(...)))
• Improves readability for nested expressions

This is especially noticeable in builder-style code and data aggregation pipelines.

Implementation notes

From my understanding, this should be feasible since all required information is already available in the AST. It can be implemented with opt-in configuration option, for example:

[format]
keep-first-argument-on-line = true

}

---

Happy to help with examples, edge cases, discussion, or coding if useful.

Thanks again for the great work!

[ntBre]

Thanks for the report and the kind words!

We currently have a preview style analogous to Black's hug_parens_with_braces_and_square_brackets preview style that will preserve the formatting in your second example, but I don't think it currently applies to calls.

https://play.ruff.rs/3ec3cb57-d450-4d2d-9b9d-33e9680c4958?secondary=Format

I'm not sure I would personally want it to apply to calls as I slightly prefer our current formatting. But I'm interested to hear what others think!

[JWCS]

I was aware of hug_parens_..., which is the sole reason my team uses preview=true, but I was struggling / disappointed to find no issues on nested calls. The best I got was searching "nested" in discussions, and discovering this entry. I've also struggled to find a similar issue on black...

The use case for us is there's often a "type conversion" going in & out of an external library api call. Standard ones in the library could be str, Path, or coercive api-modeling dataclasses

long_var_name_path: Path = Path(long_function_name(
     long, args, list, possibly splitlines, ...
))
long_var_name_path: Path = Path(
     long_function_name(
         long, args, list, possibly splitlines, ...
    )
)

We would prefer cuddling of open/close calls for 1-arg entries; arguments could be made this shouldn't happen for multiple arguments.