Formatter

ignis fmt rewrites source to a canonical layout. It parses the file, formats it, and reparses the result to confirm the tree did not change — a formatter that alters meaning is worse than no formatter, so it fails rather than write something it cannot verify.

ignis fmt src/main.ign
ignis fmt --check src/main.ign
ignis fmt --emit diff src/main.ign

Settings

They resolve in this order: built-in defaults, then [formatter] in ignis.toml, then ignisfmt.toml or an explicit --config, then CLI flags. An unknown key is a hard error, not a warning — a typo in a config file should not silently do nothing.

With use_tabs, indentation is emitted as one tab per level while indent_width still decides the logical width used for wrapping decisions.

What it normalizes

• Spacing around :, =, +, - and commas.
• Generic brackets stay tight: identity<T>, never identity < T >.
• Empty namespace, record, enum, trait and extern blocks collapse to {} on one line.
• Trailing whitespace goes, and the file ends with exactly one newline.
• Trailing commas follow the layout: a single-line parameter list or record initializer drops the final comma, a multiline one adds it.
• A single pipe expression may stay inline when it fits; a chain of two or more |> always breaks across lines.

What it preserves

Import order stays as written unless sort_imports is on, and even then sorting happens within each existing group — blank lines and comments between imports mark deliberate groups and the formatter does not merge across them.

Consecutive imports from the same path are merged into one list, unless a blank line separates them. A discard import (import _ from "...") is never merged into a named list.

A single blank line between declarations survives, because it is how you group things.

Where it stops

There is no general wrapping contract for every long expression yet. The formatter wraps what it has rules for — callable signatures, record initializers, import lists, single pipes — and when it cannot prove a rewrite is safe it fails instead of guessing. Expect that on unusual long expressions, and treat it as a missing rule rather than a bug in your code.