Formatting

nurlfmt produces one canonical layout per source file. The rules are opinionated and not configurable — the same idea as gofmt or zig fmt. ./build.sh builds it to build/nurlfmt.

./nurlfmt.sh <file.nu>              # format, print to stdout
./nurlfmt.sh --write   <file.nu> …  # rewrite in place
./nurlfmt.sh --check   <file.nu> …  # CI gate — exit 1 if not canonical
cat src.nu | ./nurlfmt.sh           # stdin → stdout

The rules

• 4 spaces per nesting level, no tabs. { opens a level and } closes it. Parentheses and brackets do not add a level — call arguments stay on one line by default.
• Exactly one space between adjacent tokens. No alignment whitespace.
• One statement per line inside a block, and one match arm per line.
• Opening { stays on the construct's line; closing } gets its own line, aligned with the opener.
• Delimiters get one inner space on each side when non-empty: ( fn arg arg ), [ T | 1 2 3 ], @ Rect { 3 7 } — and collapse to no space when empty: ( fn ), {}.
• One blank line between top-level declarations; multiple blank lines collapse to one. Do not put blank lines right after { or right before }.
• No trailing whitespace, and the file ends with exactly one newline.
• No automatic line wrapping. A long expression stays on one line unless the author already broke it across lines — nurlfmt preserves a user-introduced newline inside an expression. It does not fight it.

@ fizzbuzz i n → v {
    : ~ i i 1
    ~ <= i n {
        : b div3 == 0 % i 3
        : b div5 == 0 % i 5
        ? & div3 div5
            { ( nurl_print `FizzBuzz\n` ) }
            ? div3
                { ( nurl_print `Fizz\n` ) }
                { ( nurl_print `\n` ) }
        = i + i 1
    }
}

Idempotence

Formatting is a fixed point: nurlfmt(nurlfmt(x)) == nurlfmt(x). Every shipped .nu file round-trips byte-for-byte. Compiling the formatted output produces the same result as compiling the original. The build system checks this on every build.

Next

• Editor and tooling — the language server that runs nurlfmt on save.
• For the complete rule set with worked before/after examples, see docs/FORMAT.md.