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Formatting

Mew has one formatter, and it is the same code whether it runs in an editor or on the command line. There is nothing to configure.

What it decides​

The formatter decides indentation and the spacing between tokens. It does not decide what goes on which line, so a line break you wrote is a line break it keeps.

// Before
pub type Point{
pub field x:i32;
}
// After
pub type Point {
    pub field x: i32;
}

Runs of blank lines collapse to one, and a file that has any content at all ends with a single newline.

Running it​

mew fmt                # every .mew file under the current directory
mew fmt src            # or under a directory you name
mew fmt main.mew       # or a single file
mew fmt --check .      # report what is unformatted, write nothing, exit 1

--check is what a build runs. Mew's own build uses it to hold the sample programs to the style the formatter produces.

Why it is safe to run​

The formatter lexes its own output and compares it token by token against the input. If anything differs it returns the original unchanged, so a formatting rule cannot drop or reorder code.

info

A file that does not parse still formats. The formatter works off the token stream rather than the syntax tree, which is the normal case while you are still typing.