Single line if (without else) statement

[Cationiz3r]

Hello all, I was working on a project of mine when I found that rustfmt was always expanding short if statements.

For example, I have a function that adds cached items into a redis server, which would always fail if the items list is empty, so the following code snippet is used:

if items.is_empty() { return Ok(()); }

However, by default, rustfmt always expand it to:

if items.is_empty() {
    return Ok(());
}

which takes 2 extra lines.

Is there an option I can use to compact it into the first snippet?

[wellkilo]

There is no rustfmt option that keeps a standalone if statement such as this on one line:

if items.is_empty() { return Ok(()); }

The similarly named stable option single_line_if_else_max_width does not cover this case. It applies when an if ... else ... is formatted as a subexpression. In the current formatter, ControlFlow::new_if sets allow_single_line only when expr_type == ExprType::SubExpression, and rewrite_single_line immediately requires an else_block. See to_control_flow and rewrite_single_line.

So the idiomatic, rustfmt-stable form is the expanded block. If you must preserve the compact guard locally, the available escape hatch is:

#[rustfmt::skip]
fn add_cached(items: &[Item]) -> Result<(), Error> {
    if items.is_empty() { return Ok(()); }
    // ...
}

but #[rustfmt::skip] applies to the containing item, not just that one if, so it is usually a worse trade-off than accepting the standard layout. single_line_if_else_max_width cannot be used to change this specific statement form.

If this answers which setting applies, please mark the reply as accepted.